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Egyptian oligocene primates A review.

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YEARBOOK OF PHYSICAL ANTHROPOLOGY 38:199-238 (1995)
Egyptian Oligocene Primates: A Review
ELWYN SIMONS
Duke Primate Center, Durham, North Carolina 27705
KEY WORDS
Fayum Province, Egypt, Oligocene, Anthropoideans, Dawn
apes, propliopithecids, parapithecids, Apidium, Aegyptopithecus, Parapithecus,
Propliopithecus, Afrotarsius, primate anatomy, primate behavior, paleoecology
ABSTRACT
The study of the early anthropoids or anthropoideans from
the Oligocene badlands of the Fayum Province, Egypt, covers the greater
part of this century. This review discusses the successive stages of our
knowledge of these animals, which have become the oldest well understood
kinds of higher primates or anthropoideans. The study of the first finds,
made early in the century, is reviewed and the various interpretations of
these scanty remains are discussed. All initial discussions were based on
only four specimens. Essentially all of the early rankings made by authors
who, in many cases, had not seen the actual specimens were incorrect.
Nevertheless i t was realized that these Fayum primates were somehow the
earliest relatives of apes and monkeys then known. Prominent scholars
questioned whether one of these, Apidium, was even a primate. At the end
of the 1950s two specimens, found at the beginning of the century, were
located a t the American Museum of Natural History. Their description
kindled new interest in the Fayum primates and established that they
showed cranial characters of higher primates. Beginning in 1961 a sequence
of four periods of development in the study of these important ancient primates began. The first was a series of eight expeditions from Yale University conducted from 1961 to 1968. These cooperative projects conducted with
the Geological Survey and Mining Authority of Egypt (EGSMA) increased
the number of primate specimens from six or eight to over 500. These discoveries led to the description of new species as well as reports on the first
limb elements and cranial remains. After this phase came a period when the
desert Fayum was closed to exploration and publications were concerned
mainly with continued description of the new finds. The third major period
of research that is outlined here, between 1977 and 1989, came with renewed field work in Egypt now carried out cooperatively between Duke
University and EGSMA. The research on Fayum primates in this period
was greatly expanded, as is explained in this paper, because: 1)new techniques enabled the recovery of extensive collections of postcranial elements
as well a s skulls and facial crania, which made possible revisions of both
anatomy of the propliopithecids and parapithecids; 2) a n international interdisciplinary team published extensively on the background context for
the primates including studies on environment, dating, and geological setting; and 3) prosimians in addition to the basal Anthropoidea were found.
Since 1990 research on Fayum primates has been expanded even more to
include a larger number of researchers, many trained through field work a t
0 1995 Wiley-Liss, Inc.
200
YEARBOOK OF PHYSICAL ANTHROPOLOGY
[Vol. 38, 1995
the various Fayum localities, and although important Oligocene finds continue to be made, a whole new world of Eocene anthropoidean and prosimian primates has been discovered there. o 1995 Wiley-Liss, Inc.
During the last 34 years, finds of early higher primates in the Fayum have
revolutionized our understanding of the origins and early history of higher primates. Members of this mammal group are variously called anthropoideans, anthropoids, or simians. During most of this long period of time, fossil primates from
the Fayum were recovered from what is called the upper sequence of the Jebel
Qatrani Formation (Bown and Kraus, 1988). As a result of recent paleomagnetic
studies (Kappelman et al. 19921, this part of the Fayum section has been dated to
be of early Oligocene age. The age of the lower part of this formation, called the
lower sequence, has been debated, but most authorities agree that particularly the
lower-most site, which has produced a rich fauna of mammals called Fayum Locality 41, is of Eocene age. Since 1989, a new and intriguing primate fauna has
been described from this Eocene locality. The diversity of these newly found
Eocene Fayum collections is rapidly reaching that seen in the assemblage of primates recovered from the upper sequence. Stratigraphic relationships can be seen
in Figure 1, which displays the names and times of occurrence of Fayum primate
species. Because the Oligocene and Eocene primate faunas are separated both
taxonomically and temporally, it seems advisable to review them separately.
Hence, this paper discusses only the Oligocene primates from the upper sequence
of the Fayum badlands, together with those few specimens collected at Fayum
Locality E near the top of the lower sequence. The lower sequence primates have
been briefly reviewed recently (Simons and Rasmussen, 1995). This review article
presents a historical overview of research in the Fayum Oligocene. A simplified
outline of this history is presented in Table 1.
In a further paper now in preparation, I discuss in detail the Fayum Eocene
primates. With that discussion will be included a review of the other early Tertiary
primates from the Afro-Arabian region. These are mainly Eocene in age and come
from Morocco, Algeria, Tunisia, and from sites in the Sultanate of Oman on the
Persian Gulf.
THE FIRST OLIGOCENE PRIMATE DISCOVERIES, 1907-1908
The first evidence of primates in the Egyptian Oligocene deposits north of the
large lake called Birket Qarun, Fayum Province, Egypt, was published by Henry
Fairfield Osborn (1908). The type specimen of the primate he described, Apidium
phiomense, was based on a find made in 1907 by Richard Markgraf, a n expatriate
amateur collector. As a n alternative to being a primate, Osborn also considered
that this animal might be primitive pig-like artiodactyl. In fact, the generic name
he chose is the Latin diminutive of the ancient Egyptian name for the sacred bull,
Apis. The type specimen, a left lower jaw, was found at the onset of a n expedition
from the American Museum of Natural History, New York (AMNH), carried out by
staff members Walter Granger and George Olsen in the spring of 1907. After the
AMNH expedition ended that April, Markgraf, who lived in the Fayum at the
village of Sennuris, continued to collect. He sold further fossil primates found in
1907 and 1908 both to the American Museum and the Naturalkabinett in Stuttgart, Germany.
Three of the primate specimens Markgraf sent to Stuttgart were named in 1910
by Max Schlosser but were not described until 1911, from which date the three
names he had proposed became valid. The most complete specimen was named
Parapithecus fraasi, after the noted paleontologist Otto Fraas. This type specimen
preserves the left and right mandibular rami attached centrally and contains a
total of 15 teeth (the third antemolar tooth of the right side has been lost). A second
larger and structurally different early anthropoidean, Propliopithecus haeckeli,
consisted of a fragmentary left and right rami as well as a symphyseal fragment of
EGYPTIAN OLIGOCENE PRIMATES
Simonsl
201
-
Aegyptopithecus rewris
Propliopithecus chirobates
Apidium phiomense
Qatrania jleaglei
Parapithecus grangeri
Afroiarsius chatrathi
lorisid species
ci
E
3 0 0 Mv)
w
........
unknown
..............
I
........
*
Quarry G
Quarry
*
rL'7
v
150 M-
Quarry E
*
Quarry
E
{
Propliopi!hecus haeckeli
Propliopithecus markgrafi
Parapithecus fraasi
c
c
Propliopithecus ankeli
Apidium moustafai
Apidium b owni
Oligopilhecus savagei
Qatrania wingi
omomyid species
Catopithecus browni
9
0 M-:
Serapia eocaena
Arsinoea kallimos
Plesiopithecus teras
Fig. 1. Fayum primates. Diagrammatic partial section of Fayum Eocene, Oligocene, and Miocene sediments showing stratigraphic levels of the various quarries and the temporal distribution of the 21
described species of Fayum primates. Descriptions of two new species of prosimians from Locality 41 are
unpublished.
one individual. Taken together, these jaw fragments hold the incisor roots, the
lower canines, and the five teeth posterior to the canines on both sides. Schlosser
chose to name this species after the eminent biologist Ernst Haeckel (see Fig. 2).
The third jaw fragment contained only left first and second molars and Schlosser
described this find as Moeripithecus markgrafi, after its collector. Schlosser also
mentioned a fourth specimen in his collection (now lost), which he identified as an
indeterminate anaptomorphid. It appears that, judging from the figure in his 1911
publication, this specimen was a poorly preserved mandibular fragment of Apidium.
Of the three species Schlosser described it was evident that one, Propliopithecus
haeckeli, was dentally very similar to modern Hylobates. However, little could be
said (then or now) about Moeripithecus markgrafi because of its incompleteness.
Schlosser reasoned that the third and smallest of the three primates, Parapithecus
fraasi, might be related to Tursius or, on the other hand, belong within Homi-
202
YEARBOOK OF PHYSICAL ANTHROPOLOGY
[Vol. 38, 1995
TABLE 1 . Major periods of research on Fayum primates
Dates
1907-1912
Principal discoveries
First discoveries of Oligocene African primates:
Apidium, Parapithecus, Propliopithecus
1914-1947
No primary research, secondary views about
kinds of lineages represented; no primates
found on Berkeley Pan-African Expedition of
1947
Controversy emerges over primate status of
Apidium-status confirmed from new study;
Anthropoidean features found in a newly
located museum specimen of a frontal bone.
New Fayum expeditions yield hundreds of
primate fossils; first long hones and skull.
Description of Oligopithecus, Aeolopithecus
Aegyptopithecus, and Apidium moustafai
1948-1960
1961-1968
1969-1976
No field work in Egypt. Research continues on
earlier collections-description of skeletal
parts, skull of Aegyptopithecus, and a new
species, Parapithecus grangeri
1977-1989
Renewed collections with great increase in
number of finds, especially postcranial hones.
Major discoveries concerning sexual
dimorphism, cranial anatomy and postcranial
adaptations. Revision of propliopithecids and
parapithecids. Discovery of omomyids,
Afrotarsius, Qatrania. Interdisciplinary work
on environment, dating and geological setting
Emphasis shifts to search for Eocene primates
but Oligocene research continues to diversify
1990-1995
Collectorsiresearchers
Henry F. Osborn
Richard Markgraf
Walter Granger
Max Schlosser
W.K. Gregory
0. Ahel
Wendell Phillips
Basil Cooke
E.L. Simons
Joseph Kalin
J . Hiirzeler
J. Piveteau
E.L. Simons
D.E. Savage
G.E. Meyer
D.E. Russell
Y.S. Moustafa
L.G. Tanner
E.L. Simons
G.C. Conroy
P.D. Gingerich
E. Delson
B. el Khoshab
An interdisciplinary team
made up of dozens of
international scholars
Numerous researchers now
dominated by students
trained in the Favum
noidea, depending on the interpretation of the kinds and number of teeth this
mandible held. Determination of the dental formula depended on whether the
second pair of teeth (from the front) in the series are large lateral incisors or are
small canines. Thus either 1.1.3.3. or 2.1.2.3. might have been the correct dental
formula.
After the publication of these four species by Osborn and Schlosser more than 40
years passed without the addition of any further data about Egyptian Oligocene
primates. Most standard reference books mentioned Schlosser’s suggestion that
Propliopithecus might be related to gibbons and that Parapithecus was linked to
tarsiers and monkeys. Gregory (1922) suggested that Apidium might be related to
the Old World monkeys while Abel(1931) suggested the same (a relationship with
monkeys) for Moeripithecus markgrafi. With the entire body of data about Old
World Oligocene primates based on four specimens, very little could be concluded
about higher primate origins. In addition, no one returned to Egypt to collect more
material until 1947, when a n expedition organized by Wendell Phillips (University
of California-Berkeley) spent a few weeks in the Fayum, but no primate fossils
were recovered.
Unfortunately, the early collectors, before 1916, kept poor records; only the type
of Apidium phiomense (Osborn, 1908), has a field locality. This shows i t to have
come from the upper fossil wood zone about 100 meters below the top of the section.
First, a British scientist appointed to the Geological Survey of Egypt Beadnell
(19051,and soon thereafter Osborn (1908,19091, divided these rocks they called the
Fluviomarine Series (now termed the Jebel Qatrani Formation) into upper and
lower levels that they named Fossil Wood Zones. During the 1980s, Bown and
Simonsl
203
EGYPTIAN OLIGOCENE PRIMATES
1 cm
7
Fig. 2. Two genera of propliopithecids. Cuts showing inner (a)and outer (b)views of the right canine
through M, of Propliopithecus haeckeli; e: Crown view of same. (Reproduced from Kalin, 1961, with
permission of Masson, Cie. Paris, France.) d Posterior premolar and
of Aegyptopithecus, lower left
jaw-crown view, from Simons (19651, reprinted with permission from Nature 205:135, 1965, Macmillan
Magazines Limited.
204
YEARBOOK OF PHYSICAL ANTHROPOLOGY
[Val. 38, 1995
Kraus (1988) studied the geology and paleoenvironment of the latter formation
and divided i t into upper and lower sequences, corresponding exactly to the earlier
fossil wood zones. Their new terms solved three basic problems: 1) there is almost
no wood in the upper sequence; 2) fossil wood localities in the lower sequence are
discontinuous and concentrated only locally and in a few levels; and 3) a term such
a s Fossil Wood Zone does not adequately define sediments and contacts while the
new terms, “upper sequence” and “lower sequence,” do.
Early expeditions camped and collected almost exclusively in the lower sequence
(that is, Lower Fossil Wood Zone) near two large quarries, designated quarries A
and B, in early 1907 by Osborn. About the same time Richard Markgraf was
employed by Osborn and he gave the American Museum a small collection he had
made in the upper sequence deposits. This included the type specimen of Apidium
phiomense. The vast majority of Fayum land-mammal fossils found before 1910
came from the upper part of the lower sequence, which lies about 190 meters below
the level where the type ofApidiumphiomensewas found. The three types described
by Schlosser (1911) have no locality data and so theoretically could have come from
almost any level within the 200-meter-thick middle part of the section. None of the
types of these three species appear to belong within any of the later described species
from the upper sequence. They are smaller and more generalized, and thus probably
were found near the base of the upper sequence or below i t in the section.
Thus from 1907 to 1947, with such limited material, the main points that could
be concluded about these four first recovered Fayum primates were 1)that their
teeth were not particularly like those of prosimians or New World monkeys but
rather resembled apes or cercopithecoids; 2) that their low-crowned teeth indicated
a frugivorous diet; and 3) that they ranged in size from about the bulk of squirrels
or marmosets to about that of half-grown cats or the smallest of the living Old
World anthropoids, the “talapoin” or swamp monkey. Further, the lifestyle and
environment of these monkey-like creatures were unknown. Their exact temporal
relationships were also uncertain. Fayum mammals were largely exotic and at
that time could not be effectively correlated with the European land-mammal
faunal sequence. The Fayum continental sediments, from which these fossils came,
had not been well described geologically, could not then be dated, and were poorly
correlated. Lastly, the age of this sequence was also debated a s being either late
Eocene or early Oligocene. Much time must have elapsed during the accumulation
of these continental sediments, but the times of beginning and end of their deposition were unclear.
By the middle of the 20th century (1950-60) it was clear that these four fragmentary primate species could provide little reliable information about primate
evolutionary history or even about their own adaptations or affinities. However,
the fact that such primates could be found at all in the Egyptian Oligocene stood
as a n open invitation, even a “red flag,” signaling the need for further research
there. But no researchers went back. Perhaps this was because the Fayum is best
worked in winter when most scholars, being academicians, are teaching. Summer
temperatures in the Fayum, which can reach 138”Fahrenheit in the shade, prohibit camping there a t that time of year. Another impediment to renewed work
there may have been the belief that the workers a t the turn of the century had
already recovered almost all fossils of any importance that were to be found in the
main Fayum localities, i.e., that the Fayum localities were “worked out.” With
hindsight, we know that they did in fact locate virtually all the large mammalian
fossils such as skulls, jaws, and bones of the giant rhinoceros-like embrithopod
Arsinoitherium or of the moderately large proboscidean, Palaeomastodon. What
was actually wrong in the early years was that none of the collectors, with the
exception of Markgraf (who had found all four primate type specimens), developed
any ability to find small mammal fossils, even though Granger, a n accomplished
collector, communicated to Osborn a desire to seek them. These smaller fossils
were there in great abundance, but they had not been noticed or collected by others
than Markgraf.
Simons]
EGYPTIAN OLIGOCENE PRIMATES
205
FAYUM PRIMATE RESEARCH IN THE 1950s
Patterson (1954) wrote a provocative short paper on primate evolutionary history which underlined the point that almost all the then well-known fossil primates were clustered either in a constellation of Paleocene/Eocene lineages or
alternatively in Miocene to Holocene patterns of relationships. Only the four incomplete Fayum Oligocene primate finds then known stood anywhere between
these two great groups of fossil primates. Soon after this, in 1956, I undertook a
study of the problem of the origin of the Anthropoidea a s a dissertation project a t
Oxford University. This attempt involved analyzing all the then-known Paleocene/
Eocene primates for their potential as ancestors of the monkey-ape-human group.
In the course of this work (partly published in Simons, 1961a and 1962a), it became
clear that if more could be learned about Fayum primates i t would be important to
the understanding of primate evolutionary history. Judging mainly on the basis of
the teeth of Parapithecus and Propliopithecus, it seemed that higher primates
arose initially in Africa-nothing as anthropoid-like as they were had ever been
found on another continent. Since no continental mammal-bearing Paleocene and
Eocene sediments were known in Africa, the Fayum Oligocene was clearly the
place to look for early anthropoideans.
In 1958, while reviewing what Fayum land mammal fossils there were to be
found in museum collections, I was surprised to find three undescribed Fayum
primate fossils a t the American Museum which nearly doubled the then-known
specimens from the Fayum that had been described nearly a half-century earlier.
These new specimens consisted of 1)a right calcaneus AMNH 14607; 2) a frontal
bone AMNH 14556 (see Simons, 1959); and 3) a left, nearly edentulous, jaw ramus
AMNH 13389 (see Simons, 1961b).
Labels showed t h a t the frontal and the calcaneus had been sold to the American
Museum by Markgraf, who had collected them in 1908. The fragmentary left jaw
was collected by George Olsen in the spring of 1907 from the place now known a s
quarry M, but was mistakenly catalogued a s a carnivore. In fact, had Osborn or
others at the AMNH responded affirmatively to Markgraf‘s inquiries (in his letters
of the period to Osborn-now housed at the AMNH) whether they wanted to buy
small mammal fossils, the paleontological history of higher primates might have
been different. Among other things, the three primates which Markgraf collected
in 1909 might have gone to the AMNH rather than to the Stuttgart collections
from which Schlosser (1911) described them.
The calcaneus (AMNH 14607) was not elongated and resembled those of Eocene
lemuroids such a s Notharctus o r Adapis. As is the case for virtually every known
Fayum mammal fossil, it had been found unassociated with any other fossil. Nevertheless, this was a marmoset-sized primate calcaneus, compatible in size with
what would be expected for Apidium, as much later discoveries demonstrated
(Simons, 1959).
The primate frontal bone Markgraf found in 1908 was soon described (Simons,
1959) a t a time when I had begun to make plans to renew field collecting in the
Fayum. In 1959, this fragment was the oldest known cranial part of a primate
belonging to suborder Anthropoidea. It was specialized or derived like later anthropoideans in showing that the orbital cavity was enclosed by bone posteriorly by
zygomatic and frontal plates. This frontal (AMNH 14556) further revealed another
derived feature, full osseous fusion of the right and left frontals (typically separate
in Eocene primates) into a single bone, the metopic suture having closed at a n
early growth stage as in higher primates, rather than being retained until adulthood a s in most prosimians. Traces of the maxillofrontal suture present on the left
side of this bone show that there was no contact between the lachrymal and nasal
a s is sometimes the case in modern lemurs and ceboid monkeys. The interorbital
septum in the posterior and ventromedial part of the orbit is quite thin. The size of
the orbital opening relative to other dimensions of this frontal also indicates that
this was a diurnal animal. These and other “features of the fragmentary Fayum
frontal” confirmed for the first time in 1959 that the anthropoidean grade of pri-
206
YEARBOOK OF PHYSICAL ANTHROPOLOGY
[Vol. 38, 1995
mate evolution had been reached by early Oligocene times. Thus, dependence on
olfaction had been reduced, the frontals were fused, the orbits were protected by
bony plates, and the lifestyle was diurnal-all features characteristic of the great
majority of Anthropoidea. Later discoveries made in the Fayum confirm that this
AMNH frontal belongs with Apidium phiomense (Simons, 1995). It seems that
Markgraf discovered the type jaw of Apidzum phiomense (AMNH 13370), the calcaneus AMNH 14607, and the frontal AMNH 14556 somewhere to the north of his
camp in the vicinity of quarry A. This would put the horizon of these three fossils
as being on the upper levels in the region of present-day quarries M, P, I, and J,
wherein all subsequent specimens of Apidium phiomense have been found.
Both Piveteau (1957) and Hurzeler (1958) questioned whether Apidium and
Parapithecus were even primates. As stated above, Osborn had suggested that
Apidium might be a n artiodactyl. Hiirzeler (1958) particularly argued that Apidi u m was a condylarth with lower molar centroconid cusps resembling those of
Phenacodus. This suggested relationship was offered in spite of the fact that
Condylarthra had never been reported from Africa. Contrary to these and other
challenges of the primate status of Parapithecus and Apidium, my studies in
1956-58 confirmed the evidence for their allocation to order Primates. Moreover,
as had originally been noted by Gregory (1922), there is a greater molar cusp
resemblance (including centroconid placement) between the lower molars of a n
undoubted primate, Oreopithecus, and those of Apidium. These similarities certainly exceeded the resemblance of molars of Apidium to those of any condylarth
(Simons, 1960). The latter publication pointed out two other primate characteristics in addition to premolar and molar cusp anatomy. The first characteristic was
that the jaw ramus under the teeth was subequal in depth from front to back-not
deepening posteriorly and shallowing anteriorly as in most condylarths and artiodactyls with which Apidium had been compared. The second feature (Simons,
1960) was that the type jaw on the medial side begins to expand internally on the
inside of P4 as if to meet the symphysis, again suggesting a closed, foreshortened
tooth row as in Anthropoidea but not as in any condylarths or artiodactyls.
George Gaylord Simpson was very conversant with the interpretation of fossil
primates at that period, although regrettably he never wrote a book about primate
evolution. In the fall of 1960, when I had already booked travel to Egypt hoping to
initiate field work in the Fayum, he and I discussed my interpretation of Apidium
as definitely being a primate, rather than belonging to some other order. Admittedly, determinations on single or unique specimens are often less secure than could
be wished. I remarked jokingly to Simpson that it might be just my luck in Egypt
to find new Apidium specimens demonstrating that it could not be a primate. To
this, his indirect but prescient reply was: “That will never happen.” And i t didn’t!
The matter of the relationship, if any special one, between Apidium and Oreopithecus is discussed in Simons (1960). Oreopithecus had been described by Forsythe-Major (1872) and later published on extensively by Hurzeler (1949, 1958).
Since the 1960s, Oreopithecus has been the subject of many studies, and Apidium
has become much better known. Oreopithecus, like other Old World higher primates, most probably had a n African ancestry. Later anatomical studies alternate
a s to whether Oreopithecus represents a distinct superfamily or, more probably,
that i t is a n atypical hominoid (see Harrison, 1986, and references there cited).
Harrison (1986) has presented a case that Nyanzapithecus from the Miocene of
Kenya is related to the ancestry of Oreopithecus and that the latter also shows
resemblances to Rangwapithecus. More recent studies of Apidium (particularly
Fleagle and Simons, 1995) show i t to have been adept at springing and leaping and
to have had locomotor specializations that almost certainly exclude it from a close
relation to the ancestry of Oreopithecus.
EGYPTIAN PRIMATE DISCOVERIES OF THE 1960s
Nineteen sixty-one was a turning point in the history of the study of Egyptian
Oligocene primates, because i t was the year of publication of the last two primary
EGYPTIAN OLIGOCENE PRIMATES
Simonsl
I
1 CM
207
I
Fig. 3. Illustration of the crown view of the lower dentition of the type and only specimen of Parapithecus fruasi, from Kalin (1961), reproduced with permission of Masson Cie, Paris, France. This find
was recovered at an uncertain level in the Fayum. Parapithecus fraasi retains a single pair of milk
incisors into young adulthood. These deciduous teeth are the central pair of the four teeth on the right.
In Parapithecus grangeri, which occurs later in time, these incisors are lost at an earlier age. Species of
Parupithecus are the only higher primates known to have lost all adult lower incisors.
studies of Fayum primates found in the 1907-8 period as well as the date of my
first cooperative field research project in the Fayum (October-December 1961).
The two primary studies that were published in 1961 were written before our new
work began in the fall of that year. The more important of these reports was by
Kalin (19611,who reviewed in detail, with excellent illustrations, the three Fayum
primate types that had been less thoroughly described by Schlosser (1911). In
connection with preparation of his scientific observations on Parapithecus and
Apidium (1958), Dr. J. Hurzeler in Basel had borrowed, further cleaned, and photographed the three Fayum primate types housed a t Stuttgart. While visiting in
Basel that year Hurzeler showed me these three type specimens. On examining the
second tooth in the series of Parapithecus from the side (instead of from above only,
as in previously published illustrations), it was obvious that this tooth had a
pointed crown very much higher and longer than the tooth immediately behind it.
This tooth was much bigger in volume than the tiny pair of spatulate teeth at the
midline that could only be incisors. Always, this type specimen of Parapithecus
fraasi had been illustrated in crown view, where these disparities in size and
structure were much less obvious (see Fig. 3). I concluded (Simons, 1959) t h a t these
teeth lateral to the central incisors were the canines, thus unexpectedly giving
Parapithecus a different lower dental formula: 1.1.3.3.
Kalin had not previously published on original Tertiary fossil primates and his
discussions of the three Fayum primates a t Stuttgart were rather tentative. He
decided that Parapithecus belonged to its own superfamily, transitional from prosimians to higher primates, and that it was not a good structural antecedent to
Propliopithecus. He considered that Propliopithecus was perhaps related to the
smaller Miocene apes of Kenya, and expressed the view that relationships of Moeripithecus were most problematic, but noted that there were distinct resemblances
to Propliopithecus. Kalin’s paper constitutes a thorough discussion and documentation of the various opinions expressed about these three Fayum primates by
scientists during the more than 50 years when no new information was added.
Nevertheless, he (like all the authorities he cited) was handicapped by the limited
evidence provided by the restricted number of fossils. Following Hiirzeler’s (1958)
rejection of Apidium as a primate, Kalin failed to deal with this primate in his
otherwise detailed monograph. Nevertheless, Kalin’s discussions and bibliography
are a n important landmark and summary. His line drawings and photographic
illustrations are the best ever published of these three Fayum primate type specimens (see Figs. 2 and 3). In fact, many publications of this period were secondary,
208
YEARBOOK OF PHYSICAL ANTHROPOLOGY
[Vol. 38, 1995
having been offered by scientists who had not actually seen or studied the three
original specimens a t Stuttgart or that of Apidium in New York.
At about the same time, my report on one of the undescribed Fayum primate
specimens that had lain unnoticed in the AMNH collections for over 50 years was
published (Simons, 1961b). This was the left lower mandibular horizontal ramus
located earlier in the American Museum (AMNH 13389) that belonged to a gibbonsized primate. An error existed in the transcribed records about this specimen a t
the American Museum, for they indicated that this find was made above the
basalt, and this error was picked up (Simons, 1961b). We now know that this jaw
came from in or near quarry M, because the original field labels later turned up.
The mandible was too poorly preserved to be made a type specimen, but i t actually
was the first recovered evidence of what was soon to be named Aegyptopithecus.
The jaw was approximately a third larger than the type of Propliopithecus, and it
was distinctly different anatomically from the latter. It therefore signaled the
existence of a new kind of Fayum primate. Unlike that of Propliopithecus, this jaw
was much deeper under the canine, indicating that the canine was relatively
larger, the front premolar was elongated and sectorial, and the M, considerably
smaller relative to P4 and M,. Rather than looking like Propliopithecus, AMNH
13389 much more closely resembled mandibles of later hylobatids, of the smaller
East African Miocene primates, and of Proconsul.
Exactly 50 years had passed since publication of Schlosser's 1911 treatment of
the Fayum primates. The first Fayum expedition from Yale, which began in October 1961, was supported by a grant in geology from the United States National
Science Foundation (NSF) and by the Geological Survey of Egypt. An earlier trip
to the Fayum badlands in December of 1960 had served mainly to investigate the
feasibility of further work there and to establish credibility for applying for funds
to do so. Since then the Yale, Duke, and Cairo collections have acquired a total of
over 20,000 specimens. Even with this extensive series of materials, many new
horizons for research are now opening up, in part because of the discovery of a n
extensive Eocene fauna (Simons, 1989,1990, 1992; Simons and Rasmussen, 1995).
About half these early explorations were funded in part also by the Smithsonian
Foreign Currency Program, now discontinued in Egypt. In addition to the EGSMA
personnel, my initial research that first season was ably assisted in the field by
Y.S. Moustafa, Cairo University, D.E. Russell, Musee d'Histoire Naturelle, Paris,
and D.E. Savage, University of California, Berkeley.
It is interesting that although we then diligently searched the upper sequence
deposits in the area north, northwest, and northeast of the American Museum
campsite of 1907 (where we also camped in 19611, the primates of that first season
were found only in the lower sequence deposits (quarry E) and a t a site we designated quarry G, immediately above the boundary between the two sequences. In
1907, the American Museum team named their large mammal sites in the lower
sequence quarries A, B, and C. In 1961 we continued this naming procedure, and
our party found and worked quarries D, E, F, and G. All 11 primates found that
season came only from quarries E and G.
None of the new finds of 1961 represented the three species previously described
from the Fayum. The most important primate discovery of that first Yale field
season was a new genus and species, Oligopithecus sauagei, the type of which was
found a t quarry E, about 4 kilometers northeast of quarry A. This is a site near the
top of the lower sequence which we had located early in the season. Soon our major
excavations for the middle part of that season were shifted to quarry E and away
from the region of quarry A, where our camp was. A few days after beginning
excavations there, D.E. Savage found the specimen which became the type of
Oligopithecus sauagei (Simons, 1962b). Continued work for 2 weeks in this quarry,
with a t times up to 10 collectors, failed to produce another specimen of Oligopithecus. Despite thousands of man-hours spent at quarry E, since then no additional
jaw of this species has ever been found. After that, we shifted work to our newly
designated quarry G, which Russell, Savage, and I had located considerably higher
Simonsl
EGYPTZAN OLIGOCENE PRIMATES
209
in the section. By frustratingly slow quarrying in the consolidated matrix a t
quarry G, our team was able to discover 10 more primate specimens before the end
of that first field season. These specimens included the type and referred material
of a then-new species of primate, Apidium moustafai, named for our cooperating
researcher in Egypt, Y.S. Moustafa (Simons, 1962b).
This species is distinctly smaller and more primitive t h a n Apidium phiomense
and was recovered approximately 70 meters lower in the section than the deposits
at quarry I where the type species occurs. Dentitions of Apidium moustafai show
less molar cuspidation, and some individuals have relatively smaller third molars.
In later field seasons, upper and lower jaws of Apidium moustafai were found in
considerable numbers along with a large number of isolated, unworn teeth. In
Figure 4A, isolated upper teeth of Apidium moustafai are illustrated. Figure 4B
shows lower teeth of the type of the upper sequence species of Apidium phiomense.
During 1962 and 1963, we established our field camps in a wadi-an Arabic word
meaning valley-only a few hundred yards southeast of quarry G and worked the
latter quarry extensively. Little did we know at that time that we were camped
only a few yards from what was to become one of our more important localities,
quarry V.
The two new species we had located a t quarries G and E were described in
August 1962 before the second field season (Simons, 196213). These finds of Apidiu m moustafai made i t possible to draw a number of new anatomical and taxonomic
conclusions and it became clear that the relatively small canines and similar lower
premolars justified placing Apidium with Parapithecus in the same family Parapithecidae (Kalin, 1961). Some of the new lower jaws showed that there were three
premolars, together with canines that are somewhat small relative to these teeth
of other early anthropoideans but comparatively large compared with anaptomorphid or omomyid canines. This showed also that the anteriormost was not a canine,
as some had supposed for Parapithecus fraasi. Upper premolars were also three in
number, and they exhibited a large central cone between inner and outer cusps.
This is a n unusual added cusp, not normally seen in anthropoideans, but resembling a somewhat similar cusp seen in upper premolars of carpolestids and plesiadapids. Apidium jaws from quarry G, which preserved the anterior end of the
mandible, showed that a s in Anthropoidea generally, the anterior symphyseal
suture between the two mandibular rami was completely fused in the youngest
individual we recovered. Jaws with incisor root sockets indicated that there were
probably two pairs of teeth between the lower canines, so that Apidium, we
thought, had a dental formula of 2.1.3.3. In spite of a large number of Apidium
moustafai mandibles and maxillae which we eventually accumulated from quarry
G, no cranial finds, and only one calcaneus, were ever recovered, so little could be
inferred about overall anatomy or lifestyle of Apidium. Apidium did not have a n
elongated foot for clinging and leaping, as do some prosimians. Its rounded, flattened-off teeth suggested fruit eating.
The assessment of Oligopithecus savagei made a quite different story from that
of Apidium moustafai. These two species described in 1962 are a s different in
dental anatomy a s are any two of the other African Oligocene primates. The three
lower premolars of Apidium increase in size and complexity from front to back but,
as the canines are comparatively small, there is no sectorial blade on the small P2.
In Oligopithecus savagei, on the other hand, there are elongate P,’s with a prominent wear facet t h a t honed against a n opposing facet on the upper canines, thus
third and fourth premolars are distinctly heteromorphic, and second premolars are
lost. In contrast, the three premolars of Apidium are clearly homomorphic. The
loss of second premolars is a derived catarrhine feature. These distinctions of the
anterior dental mechanism of Oligopithecus led to the suggestion (Simons, 1962b)
that the species Oligopithecus savagei could be related to the ancestry of catarrhine
monkeys, where sectorial premolars are typical. As oligopithecines have become
better known, they are now ranked with the propliopithecids. In fact, the premolar
honing mechanism, with loss of second premolars, is equally a resemblance to both
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Fig. 4. A Composite upper dentition of Apidium moustufui from quarry G, Fayum. Note the central
cusp on all three premolars and the reduced protocone, rounded para- and metaconules, and the enlarged
hypocone and cusped lingual cingulum. B: Crown view of the lower dentition of the type specimen of
Apidium phiomense showing distinct centroconids on all three molars. Note the increase in length of the
molars from M, to M, and the polycuspidation of these teeth.
Cercopithecoidea and Hominoidea. Like some omomyids and adapids, the M, of
Oligopithecus retains a paraconid cusp which is reduced to a crest in M,. Third
molars are unknown. Extensive subsequent work at quarry E-across more than
two decades-has yielded only one isolated upper molar and a few lower teeth
which could belong to Oligopithecus sauagei. These additional specimens were
described in Simons and Rasmussen (1988).More recently Rasmussen and Simons
(1992) have reviewed the paleobiology of the oligopithecine subfamily of propliopithecids.
Close to the end of our third field season in the Fagum in December 1963, we
discovered quarry I in the upper sequence deposits. We saw the many bones and
white coprolites while driving by in a field vehicle. The major series of stream
channel and point bar deposits i t represents had been weathered in modern times
into a hill covered with large fossil jaws, limb bones, and skulls. Our arrival at the
spot was most exciting, a s there was absolutely no evidence that anyone had ever
Simonsl
EGYPTIAN OLIGOCENE PRIMATES
211
collected fossils there. For instance, there was a complete absence of the trenching
by early workers (probably Markgraf) that can be seen in the vicinity of quarries
A, B, and C , which were worked from 1900 through 1907 and intermittently later
by Markgraf until as late as 1912. Our very extensive surveys strongly indicate
that all obvious large fossils exposed by weathering in the central fossiliferous area
of the Fayum badlands were found and collected in the early years of this century
except for this one undetected fossiliferous area: quarry I.
The initial fossil finds at quarry I were made near its northern end. As stated,
the point-bar gravel sequence making up this quarry makes a n erosional high at
its northern end, and as we collected southward from there in December 1962 a t a
point along the southeast side of this high, one of the workers and I each found a
primate jaw on the undisturbed serir surface at almost the same moment. Only two
other primate jaws, out of nearly a thousand now recovered, have ever been found
on undisturbed gravel-covered surfaces in the Fayum.
These two surface finds of primates made at quarry I in 1962-one a n Apidium
and the other with badly wind-eroded teeth perhaps belonging to Propliopithecusgave promise that more primates would be found there by excavating. We began
such digging in 1963. Soon the type jaws and two other jaw fragments of Aegyptopithecus zeuxis came to light. Since the sediments in this part of quarry I were
unconsolidated, we were quarrying by brushing and sweeping with house-painters
brushes. A considerable area of the top of the quarry I ridge had been exposed by
our work when one night there was a severe windstorm. While collecting in quarry
I the following morning we noticed that much sand had been blown out of the
quarry in just one night and that many new fossils were exposed. This process
resembled a phenomenon I had been familiar with after collecting Paleocene fossils
for Princeton University in the 1950s from sandy “blow-outs’’ in the Medicine
Rocks region of southeastern Montana. That same day, I discovered what appeared
to be a n entirely new kind of dawn ape mandible that had been exposed by the
previous night’s windstorm. It preserved the entire tooth-bearing part of the mandible, with highly eroded teeth. This find became the type of Aeolopithecus chirobates (Simons, 1965).
From that time on, we increasingly saw the importance of wind-erosion as a n aid
to finding Fayum primate fossils. Large surface areas of quarry I were cleaned of
the “lagging” desert gravel pavement, thus accelerating wind-erosion of the loose
sand. Small-sized primates as well as associated rodents, insectivores, and bats are
almost never found on the unexposed serir covered by desert pavement. The quarry
must be treated by removal of the surface gravel before wind erosion exposes the
smallest mammals. During the remaining field seasons of the 1960s, dozens of
Apidium jaws and smaller numbers of Parapithecus and Aegyptopithecus jaws
were found in quarry I, but nothing further of Aeolopithecus was located. We did,
however, find fossils t h a t resembled Propliopithecus. The two new taxa, Aegyptopithecus zeuxis and Aeolopithecus chirobates, were clearly ape-like forms or hominoids, and at first neither of them appeared to be specifically or even generically
identical to the two other ape-like Fayum species, Propliopithecus haeckeli and
Moeripithecus markgrafi, Schlosser had described in 1911. All these early anthropoidians have very simple lower teeth that, except for greater reduction of their M,
paraconid, resemble lower teeth of Cantius, see Simons 1962a.
At first tentatively (Simons, 1967b) and then without reservation (Simons,
1967~1,the genotype species of Moeripithecus markgrafi was allocated to Schlosser’s other propliopithecid genus, Propliopithecus. This came after direct study of all
original specimens then known at New Haven and Stuttgart. In Propliopithecus
markgrafi, the M, hypoconid is almost confluent with the entoconid, unlike in
other propliopithecid species, and resembles in this detail Oligopithecus. This feature is perhaps sufficient to in part justify a species distinction for the specimen.
The two molars a r e constricted medially (bucco-lingually), so that these teeth
appear more quadrate and anteroposteriorly shorter than in Aegyptopithecus. Molar crowns of Propliopithecus markgrafi look constricted, because this type is a
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young individual, with little worn teeth. Laterally both teeth have a broad singular shelf reminiscent of Propliopithecus haeckeli. This type specimen is a most
incomplete fragment which today would not be used as a type specimen and certainly not when its stratigraphic provenance is unknown. One can only suggest
that it may be the same species a s certain worn, isolated lower molars from quarry
G. No fossil with the molar features of Propliopithecus rnarkgrafi has been found in
the upper level of quarries I and M but some from quarry G have been tentatively
allocated to i t on specimen labels. Subsequent writers or revisers almost invariably
cannot agree about what to rank with such incomplete type specimens, and placing
later found material with such a n inadequate type can radically alter the concept
of the genus or species concerned. We now know that propliopithecids have very
simple lower first and second molars, with a very limited number of simplified
cusps arranged in the so-called “Dryopithecus pattern” and that there is nothing
distinctive about the two teeth in Schlosser’s type. Of course, a t the time Schlosser
was writing, there was little or no awareness of the problem of inadequate types
caused by insufficient type material. In the original description it was indicated
that Aegyptopithecus more nearly resembled Proconsul and other dryopithecine
apes, whereas Aeolopithecus (now Propliopithecus) seemed closer to the ancestry of
gibbons (Simons, 1965).
Aegyptopithecus zeuxis, the first of the two new species of 1965, is much larger
than Propliopithecus haeckeli. Combining nine measurements, the type of the latter averages only about 82% as large as the type of Aegyptopithecus zeuxis. Simons
(1965) pointed out that a single tooth, the sole potentially assignable specimen of
Propliopithecus haeckeli with a known locality, comes from quarry G. However, i t
is smaller than all other propliopithecid teeth ever found a t quarry G. As a single
lower first molar, it is inadequate to definitely confirm whether or not Propliopithecus haeckeli actually occurs at that level. However, in that paper as well a s in
Simons (1967131, it was suggested that the type of Propliopithecus haeckeli was
most likely found somewhere in the lower part of the section from quarry G on
down to the level of quarry A about 120 meters below it. All known specimens of
Aegyptopithecus come from quarries I, M, and P, which are located stratigraphically almost 200 meters above quarry A and 80 meters above quarry V. Quite apart
from the question of stratigraphic and presumed temporal separation of these two
early catarrhines lies the fact that no specimen of the absolute size or morphology
of Propliopithecus haeckeli has ever been found in the upper levels.
This work of the 1960s stressed that Aegyptopithecus zeuxis differs from Propliopithecus haeckeli in having much larger canines and a n anteriorly deep mandibular horizontal ramus while that of Propliopithecus haeckeli is less deep anteriorly, maintaining from front to back a more or less uniform depth. In
Propliopithecus, the MI and M, are the same approximate size (see Fig. 21, and P,
is relatively small in relation to M,. In Aegyptopithecus, these proportions are
quite different: M, is much larger than MI and P, large relative to MI. The lower
molar cusps are enlarged, swollen, or “inflated” in Aegyptopithecus and therefore
round out into the sides of the tooth rather than showing more centrally located
cones placed on a broader tooth base with distinctly developed anterior, lateral,
and posterior cingula, as is to be seen in Propliopithecus haeckeli. Mandibles of
Propliopithecus chirobates from the upper sequence hold all these same features of
difference for Aegyptopithecus that are to be seen in the holotype. J a w structures
of these two early anthropoids differ throughout, because muscular insertion rugosities are greatly developed in many jaws of Aegyptopithecus. The ascending
mandibular ramus is 40% to 50% broader compared to depth under M, in Aegyptopithecus than it is in Propliopithecus haeckeli. Although species of these two
genera are clearly related and belong in the same family, Propliopithecus and
Aegyptopithecus are clearly distinct. They are at least as different in comparable
parts of jaws and teeth a s are the modern chimpanzee and gorilla. Their very
distinct differences in tooth-cusp shape and clearly demonstrable differences in the
relative size proportions of all the post-incisors teeth (even the incisors may differ)
Simons]
EGYPTIAN OLIGOCENE PRIMATES
213
together with different robustness, and distinctions in proportions of all parts of
the mandibular rami suggest that species of these two genera differed in diet,
growth rates, and adaptive function. Therefore, the casual allocations of Propliopithecus to Pliopithecus (Simonetta, 1957) or equally of Aegyptopithecus to Propliopithecus (Gingerich, 1978; Szalay and Delson, 1979; Harrison, 1987) are incorrect.
No matter how convenient a simplification such a “lumping” might be, these are
definitely two distinct genera.
Simons (1965) described a second propliopithecid taxon from quarry 1. This was
Aeolopithecus chirobates, the one whose type had been exposed by a windstorm.
This type consisted of centrally fused mandibular horizontal rami with all lower
teeth save the incisors, whose relatively large sockets were well preserved. Compared to the Aegyptopithecus finds known in 1965, this jaw was small, about the
size of the type of Propliopithecus haeckeli but with much larger molars and more
robust anteriorly than is the latter. Unlike the case in Propliopithecus haeckeli, the
canines and incisor sockets of Aeolopithecus were very large relative to cheek tooth
size; P3 and P4 are distinctly heteromorphic rather than being similar sized, as
they are in the type of Propliopithecus haeckeli. The teeth of Aeolopithecus chirobates were marred by enamel erosion, possibly by sand-blasting from wind, or from
chemical solution of the tooth enamel. In consequence of this, exact crown patterns
could not be determined. Even so, there was little similarity between this jaw and
the types of Apidium, Parapithecus, or Oligopithecus. The
of Moeripithecus
and Aeolopithecus could not be compared because of the poor condition of these
teeth in the type of Aeolopithecus.
About a year after it was first located, Simons (1967a) reported and figured a
newly discovered and nearly complete skull of Aegyptopithecus that had been
found at the close of the 1966 season (see Fig. 5). The find had been made by Grant
E. Meyer, who, while crawling alone on quarry M, noticed orbits and brow ridges
protruding from the sand. Highly excited, but fearing that in situ digging could
cause irreparable damage, he encased the whole spot in penetrating glue and took
out a large block, but was not sure just what he had. It was only later after careful
preparation in the Yale laboratory that most of a skull emerged. Several hundred
hours have been spent on its cleaning. Later that year, Simons (1967b) pointed out
that the then-known Egyptian Oligocene primate species came from three different faunal horizons: quarry E being lowermost with Oligopithecus sauagei; quarry
G in the middle stratigraphically with Apidium moustafai, and a species of
Propliopithecus; and a t the top quarries I and M, where Aegyptopithecus zeuxis,
Aeolopithecus chirobates, Apidium phiomense as well as then-undescribed species
of both Parapithecus and Propliopithecus were found. Early geologic sections indicated that quarries E and G were separated by about 45 to 50 meters and quarry
G from the I/M level by about the same. More accurate recent section measuring by
Bown and Kraus (1988) put the three levels much farther apart. About 75 meters
separate quarries E and G and 68 to 70 meters lie between quarry G and I/M (see
Fig. 1).The mammalian faunal composition of each of these main horizons is
distinctly different, and no mammalian species is known to occur a t all three
levels. The implication was that they could represent early, middle, and late Oligocene times.’
The 1966 skull of Aegyptopithecus zeuxis proved to be a n almost perfect connecting link in primate history and strongly suggested for this Fayum primate a n
ancestral relationship to Proconsul and the dryopithecine apes (see Simons,
1967a). There is a mosaic of primitive, prosimian-like, and derived features in
combination in one species. For instance, the closure of the frontals into one bone
and the full development of postorbital closure are derived, “modern” anthropoid
features, while the large ascending expanded wing of the premaxilla and the only
‘Much more recent work of Fleagle et al., (1986) shows that the Jebel Qatrani capping basalt is 31 2 one
million years old. Kappelman et al., (1992)provided a younger date for this basalt but the sample was not taken
from the lowermost of four basalt flows (T.M. Bown, pers. comm.) and therefore does not alter the foregoing date.
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YEARBOOK OF PHYSICAL ANTHROPOLOGY
[Vol. 38, 1995
Fig. 5. Frontal view of the 1966 skull of a young male individual of Aegyptopithecus zeuxis, mounted
together with a n independently discovered male mandible of compatible size. Note frontal fusion, enclosed eyesockets, large premaxillae, and deep, robust mandible.
marginally ossified ectotympanic tube ending at the margin of the auditory opening are primitive, resembling lorisoids and the platyrrhines. Aegyptopithecus was
a monkey or lemur-like “tree-dweller, still carrying a tail in spite of anatomical
advances such as suture-closing and hominoid teeth. . . . The animal was evidently
pursuing an arboreal pattern of life directing it along the evolutionary path leading from lemur-like and monkey-like forms to apes and perhaps ultimately to
Simonsl
EGYPTIAN OLIGOCENE PRIMATES
215
man” (Simons, 1967b:g). While recognizing the nature of Aegyptopithecus as a n
evolutionary linking form, it is convenient to refer to it and Propliopithecus as
“dawn apes” because of their distinctly ape-like teeth and face even though this is
not meant to imply they are specifically related to modern apes.
After the seasons of 1964, 1965, and 1966, there could be no question that
Apidium phiomense is the commonest mammal occurring in the upper sequence,
Jebel Qatrani Formation. As the number of Apidium jaws discovered through
induced wind erosion from quarry I rose to many score, it became apparent that
this parapithecid had a fused mandibular symphysis and a fused metopic suture of
the frontals. The frontal earlier described (Simons, 1959) was shown to be of Apidium, because a number of less-well preserved frontals like it had been found in the
quarry I layers where Apidium was so abundant. Both the 1959 frontal and a
then-new maxillary fragment bearing teeth from quarry M demonstrated postorbital closure. Also, toward the close of the 1960s it was possible to present a new
and different interpretation of the parapithecids, because specimens of Apidium
from quarry I showed that the dental formula both above and below was 2.1.3.3.
Specimens of a new, larger and somewhat divergent species of Parapithecus were
discovered in quarry I in the mid-1960s but it was not immediately named. In this
period we also began to find many primate limb bones almost all of which were of
a size appropriate to belong to Apidium phiomense, much the commonest primate
found there. In 1965 Grant Meyer and I discovered a new quarry, called quarry M,
located about 1kilometer west of quarry I, but a t first primates found there were
few. Apart from the 1966 skull of Aegyptopithecus found by Grant Meyer, the
maxilla of Apidium just mentioned, and one Aegyptopithecus ulna (not at first
identified as such), no small mammals or other primate specimens came from
quarry M in the 1960s.
Simons (197413) described the then-new, large species of Parapithecus from the
upper level at quarry I naming it Parapithecus grangeri. It is 10% to 25% larger
than the same measures of the type of Parapithecus fraasi, which has a slightly
larger M, relative to M2 and a more gracile mandible than th a t of Parapithecus
grangeri. The horizontal ramus of Parapithecus grangeri deepens posteriorly while
that of Parapithecus fraasi does not. The lower molars of Parapithecus grangeri are
semibilophodont with reduced hypoconulid and paraconid crest. Unlike tooth
structure in species of Apidium, Parapithecus grangeri molars and premolars are
reminiscent of modern small African monkeys, particularly Cercopithecus talapoin, and also of Prohylobates tandyi from the Miocene of Egypt. For these reasons,
I concluded that Parapithecus grangeri was in or near the ancestry of cercopithecoid monkeys (Simons 1970, 1972, 197413). Simons and Delson (1978) further discussed the phyletic position of the parapithecids a t some length and presented
arguments for and against their relationship to catarrhine monkeys. It was agreed
that they had reached the “monkey” level of organization.2
Specimens of the new Parapithecus species from quarry I suggested that interpretation of the dental formula of Parapithecus fraasi given by Kalin (1961) was
wrong. This was because the type of Parapithecus fraasi had a n irregular break in
the symphyseal region that might possibly have been a symphyseal suture. This
crack in the unique type was shown to be a fracture because all anterior parapithecid mandibular fragments subsequently found were solidly fused across the
midline. Originally, when Markgraf collected the type specimen of Parapithecus
fraasi one could suppose that the anterior symphyseal region had fallen apart and
the fragile rims of all incisor sockets were broken away, leaving only two loose
incisors that were glued on much later. Because this might have happened (and
since primates normally have two pairs of lower incisors) it was first concluded
(Simons, 1967) that Parapithecus was like Apidium in having four lower incisors.
‘The demonstration by Kay and Simons (1983)that Purupithecus has no permanent lower incisors rules it out
as a direct ancestor of later catarrhines. Studies by Fleagle and Kay (19871 deduced that parapithecids were a
sister group to all other Anthropoidea.
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YEARBOOK OF PHYSICAL ANTHROPOLOGY
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Afterwards we found that Parapithecus did not have permanent lower incisors a t
all, but instead retained a pair of milk incisors into early adulthood (Kay and
Simons, 1983). In the type of Parapithecus fraasi the two small central incisors are
a much lighter color than the other teeth and can be presumed to be milk teeth.
Milk teeth often stain lighter than permanent teeth during fossilization. Another
unintentional error was that the cracked area of the anterior symphysis in the type
specimen of Parapithecus fraasi had been glued together, giving this jaw a coincidental resemblance to the V-shaped dental arcade of Tarsius. Parapithecus
grangeri does not have a V-shaped dental arcade.
Taken altogether the many specimens of Parapithecus and Apidium found in the
1960s confirmed that these animals had reached the “monkey” grade of organization, regardless of whether they are directly related or not to living monkey
groups. It had been shown that they were neither prosimians nor hominoids and
certainly not non-primates. Their teeth showed certain shared derived characters
with those of the Fayum propliopithecids, but gave no evidence that these groups
could belong in the same family or even superfamily. Although many jaws with
about two dozen limb bone fragments of Apidium were found a t quarry I in the
1960s these did not immediately indicate much about the broader taxonomic relationships or locomotor function of parapithecids. None of the postcranial long
bones were complete, but parts of several isolated humeri, a s well as one distal
femoral epiphysis, and tali, calcanei, vertebrae, sacral fragments, and toe bones
were found in the 1960s.
After the closing of field work in January 1967, the Egyptiadlsraeli war of June
1967 seriously affected further research in the Fayum badlands. Following very
brief visits to these Egyptian Oligocene sites in the fall of 1967 and 1968 the
Egyptian government closed this part of the desert to all visitors, Egyptians and
foreigners alike. This situation finally cut off field work there, and the ban was to
continue for 8 years more. In consequence, no funding for renewed EgyptianAmerican cooperative field seasons was secured until October 1977.
LABORATORY RESEARCH ON EGYPTIAN PRIMATES IN THE EARLY 1970s
The cessation of field work in the 1960s left several primary questions about
Oligocene primates unanswered. Some of these revolved around the relationships
of the three propliopithecid taxa then recognized. These taxa together with Oligopithecus all resembled later catarrhine primates in having two premolars. By
1968,there were six partial mandibles of Aegyptopithecus (all of which later proved
to be males), another very damaged one that might be Propliopithecus, some isolated teeth from quarry G, and the four unique type specimens of Oligopithecus
savagei, Aeolopithecus chirobates, Propliopithecus haeckeli, and Propliopithecus
markgrafi. With such limited samples almost nothing could be said about morphological variation in these earliest anthropoideans. It was nearly impossible to
distinguish individual characteristics and differences due to sexual dimorphism
from what might be valid taxonomic differences. It was obvious that much more
material of these early catarrhines needed to be collected before their lifestyles
(behavioral adaptations-ecological setting) and taxonomic relationships could be
made clear. We then believed that we might reach old age or retirement before
collecting in Egypt would again be possible.
Even though we were not able to make new field collections, several advances in
understanding Fayum primates were made during the early 1970s. A report was
published on what was then known ofParapithecus and Apidium (Simons, 1970)as
well a s a textbook review of all the Fayum primates (Simons, 1972). Szalay (1970)
published a brief note contending that the Asian form Amphipithecus and the
Fayum genus Oligopithecus were both prosimians. Simons (1971) reasserted that
both, but especially Oligopithecus, had anthropoid affinities. An Apidium petrosal
and what we then believed to be a n associated temporal were described (Gingerich,
1973). Unfortunately, this temporal was shown not to be of a primate (Cartmill et
Simons]
EGYPTIAN OLIGOCENE PRIMATES
217
al., 1981). Simons (1974a) demonstrated, contra Andrews (19701, that Aegyptopithecus did not survive into the Miocene of East Africa but did show that it is more
closely related to Proconsul than to the smaller African Miocene apes. Conroy et al.
(1975) reported on a series of juvenile parapithecid mandibles. These jaws, with
various milk teeth and unerupted teeth, demonstrated that parapithecids had a
primitive premolar eruption sequence: P2-P,-P,.
Their study also showed that
these “monkeys” exhibit a derived feature: delayed canine eruption. This resembled catarrhines, and not prosimians or platyrrhines. As has been mentioned,
Simons (1974b) described a new parapithecid species Parapithecus grangeri and
discussed its relationships. An ulna of Aegyptopithecus from quarry M was identified and described by Fleagle et al. (1975). Conroy (1976) analysed all the postcranial remains then known of parapithecids from the Fayum. In 1978, Evolution
ofAfrican Mammals was published by Harvard University Press. Articles in it
(which were actually written long before publication in 1978) summarized the
parapithecids (Simons and Delson, 1978)and the Fayum apes (Simons et al., 1978).
Toward the end of the decade, but before the new finds of the late 1970s could be
appreciated, Gingerich (1978) published a new genus Simonsius for Parapithecus
grangeri and suggested that all the Fayum propliopithecids, then considered hominoids, might belong to the same genus.
The referred ulna of Aegyptopithecus described by Fleagle et al. (1975) provided
the first piece in the puzzle of understanding the locomotor adaptations of the
Oligocene catarrhines. On first examination in the field in 1967 and because of its
robustness, this ulna was regarded as perhaps having come from a small carnivore.
Its possible allocation to Aegyptopithecus was discussed at the time of discovery,
but uncertainty led to its having entered the field catalogue as “?carnivore.” Some
years later, Fleagle, noticed the specimen in the Yale carnivore collections and
convincingly demonstrated its resemblance to the Miocene apes Pliopithecus and
Proconsul. Fleagle et al. (1975) published on this first long bone of an Oligocene
primate to be described. We also determined that this ulna resembled most closely,
among living primates, species of the genera Lagothrix and Alouatta. This ulna
demonstrated that Aegyptopithecus had comparatively short and robust limb
bones. Anatomical details suggested the species was good at climbing and was an
arboreal quadruped.
We learned the hard way that this ulna did not correspond to preconceived
notions then held as to what an archaic catarrhine limb-bone should look like. In
fact, our manuscript describing it was returned by reviewers more than once with
the suggestion that the find was not a primate bone but belonged to an arboreal
carnivore, even though no teeth of arboreal carnivores had (or have) ever been
discovered in the Fayum. It seemed that what some scientists expected to find was
that an early catarrhine should be a more gracile, clinging, and leaping ancestor.
When something quite different actually turned up they had diffkulty accepting
the morphology it demonstrated. Such circumstances have led me to the conclusion
that ancient fossil forms can seldom be predicted by induction, or recreated by
inference. What happened in the past is disclosed by finding actual fossils.
At first, the identification of the 1967 ulna as of Aegyptopithecus zeuxis was
based on provenance. It came from the same site (quarry MI as the Aegyptopithecus
jaws and skull. It was also compatible in size, there being no other known primate
in the Egyptian Oligocene in the size range ofAegyptopithecusz e u i s . Over a dozen
whole or partial humeri and several other ulnae found in quarries M and I since
then confirm the original allocation. Anatomical analysis of this first ulna showed
that the animal was a generalized, stocky arboreal quadruped, probably good at
maintaining forelimb stability during climbing and forelimb suspension. Analysis
of this ulna showed for the first time that archaic catarrhines did not particularly
resemble modern Cercopithecoidea postcranially but rather this bone looked like
ulnae seen in the larger Ceboidea. We believed the resemblance was an adaptive
similarity that did not imply a special phyletic relationship. There was no evidence
at all of incipient arm-swinging abilities, nor did the bone look like those of cling-
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ing and leaping prosimians such as Propithecus or Notharctus. Apart from this
ulna, the caudal vertebra already mentioned, one hallucial metatarsal, and one
phalanx, no other evidence existed a t the close of the 1960s about the postcranial
anatomy of the propliopithecids (see also Conroy, 1976a, 1976b; and Preuschoft,
1974).
In the 1970s some of the postcranial adaptations of Fayum primates first began
to be understood. Conroy (1976a) found that the postcranial bones of Apidium in
various ways resembled those of South American monkeys from both morphological and statistical analyses. Conroy (1976a) dealt with 25 postcranials, one of
which was the ulna of Aegyptopithecus from quarry M. All the other bones were
much smaller and where there was multiple representation of limb bones (humerus, ulna, radius, talus, calcaneus) each type had the same morphology. Conroy’s thorough discussion established that these were, indeed, all primate bones,
most probably belonging to Apidium phiomense. Conroy concluded that taken
altogether these arm bones and tarsal elements indicated that Apidium had a
locomotor adaptation reminiscent of the gracile leaping and running South American monkeys such as Saimiri or Cebus.
Kay (1977) discussed the molar occlusion patterns in Egyptian Oligocene primates. He found that the functional dental adaptations of Parapithecus and Apidiurn resemble catarrhine monkeys and apes, not ceboids, and that except for Oligopithecus savagei, all Fayum species possess a shared-derived feature-a facet
(called facet X) not otherwise found outside the catarrhines. The dental adaptations of Aegyptopithecus resemble those of later apes. The ecological adaptations of
the Oligocene primates of Egypt were summarized by Kay and Simons (1980). In
this paper we estimated body mass for the nine species: The smallest is Apidium
moustafai at about 700 grams and the largest is Aegyptopithecus zeuxis a t about
6,000 grams. All species are larger than any living insectivorous primate species.
Because of a greater development of shearing facets, Parapithecus grangeri may
have had a greater element of fiber in its diet. This means that it might have been
partially folivorous. All other Fayum primates, both ape-like and monkey-like
species have molar morphologies consistent with frugivorous diets. Orbital anatomy, where known, indicated that all these species were diurnal. Kay and Simons
(1980) also provides a plot of shearing quotients (their Tables IV and V) that place
Parapithecus grangeri far from the other species but nearer to the quotient of
Gorilla gorilla. Aegyptopithecus zeuxis, Apidium moustafai, and Propliopithecus
chirobates plot very close to Pan troglodytes while Parapithecus fraasi, Propliopithecus markgrafi, and Apidium phiomense are closer to Pongo pygmaeus.
THE DUKE-CAIRO EXPEDITIONS (FROM 1977 TO 1989)
After obtaining permission in 1976 from the Geological Survey of Egypt to resume field work in the Fayum, we were awarded a n NSF grant in the spring of
1977 to support renewed research there. At about that same time I transferred my
employment, and the Fayum project, to Duke University. During the period from
1967 to 1977 there were many important advances in the techniques and procedures used in the analysis of the anatomy of fossil primates, in collecting methods,
and in paleobotany, biostratigraphy, sedimentology, and taphonomy. Thus in 1977
we could approach our field program in a n entirely new interdisciplinary way and
could, as well, contribute more directly to the training of Egyptian geologists. This
ongoing phase of our field research program has proven of great mutual benefit.
The research done by scientists a t the Egyptian Geological Survey and Geological
Museum, Cairo, together with our international team produced a flood of new
information about the Egyptian Oligocene. The work of this period differs from
that of the 1960s in three primary aspects: 1) the number of identified primate
postcranial bones had dramatically increased from the 25 to 30 pieces known in the
1960s to a number in excess of 200 by 1979; 2) the number of skull fragments and
upper and lower jaws of Aegyptopithecus and Propliopithecus found and identified
had risen from 15 or so fossils identified up to 1967 to over 80 by 1979; and 3)
Simons]
EGYPTIAN OLIGOCENE PRIMATES
219
extensive new environmental evidence was gathered and this has continued up to
the present. This includes analysis of birds, trace fossils, fossil leaves, fruits, and
paleosols. In fact, the world’s largest continental ichnofossil series has been described from the Fayum. There are also new data on the environment of the Fayum
primates derived from current geological studies. This work-in-progress includes
modern investigation of general geology, biostratigraphy, and taphonomy together
with studies of paleosols and lithology (Bown et al., 1982, Bown, 1982, Bown and
Kraus, 1988, and Genise and Bown, 1994).
Field collecting in the Fayum Oligocene during the lake 1970s proved highly
successful, particularly with respect to the primate and other mammalian finds
made in the upper sequence. During these years, about 1,400 mammalian specimens were found and divided between Cairo and Duke, including about 150 primates. These finds tripled the known number of propliopithecid specimens and
provided about four times as many post-cranial elements as were known before,
including the most complete specimens of many taxa. For the first time we had
enough information to be able to assess the functional anatomy of the limb structure in parapithecids and to evaluate the dental evidence for diet and sexual
dimorphism in these apes and Apidium phiomense.
A major objective of the late 1970s was to expand the existing highly productive
quarries of the upper sequence deposits and to identify new microfossil localities in
the lower sequence. Both objectives were accomplished. Beginning in 1977, quarries I and M, which have yielded the vast majority of primate fossils from the
Fayum, consisted of previously exposed surfaces of approximately 35 x 60 meters
and 50 x 70 meters respectively. During the next three seasons, the size of these
quarries was greatly expanded so that wind erosion would expose fossils by the
wind-harvesting method discussed. This expansion produced many new primates.
In 1977, for instance, four distal humeral fragments of propliopithecids were recovered and were reported by Fleagle and Simons (1978). Two fragments were
about the size of humeri in extant Alouatta and these we assigned to Aegyptopithecus. Two still smaller fragments, about the size of distal humeral ends of the
bearded saki (Chiropotes),we suggested might belong to a species of Propliopithecus. We concluded that this part of the skeleton, the ellbow region, is highly
diagnostic for separating living monkeys and apes. Gebo i3nd Simons (1984) detected puncture marks on some of these humeral fragments and on one mandible
of Aegyptopithecus that indicate possible predation by carnivores. These humeral
ends showed that just as in Apidium and in many extant platyrrhines and prosimians, Aegyptopithecus shared a complex of primitive features such as a large
medial epicondyle, a comparatively broad trochlea, and a well developed brachialis
flange. Both modern apes and cercopithecoids possess derived features not seen in
Oligocene catarrhines. Thus we stressed that it is a false dichotomy to consider
these Oligocene forms either “ape-like” or Old-world monkey-like. Rather, the
closest resemblances are with the larger South American quadrupedal monkeys
such as Alouatta.
In the late 1970s extended sweeping activities also led to some expansions of
quarries J, 0, P, and R in the upper sequence a s well as the recovery of a variety
of fossils in outlying spots. During the period there were frequent visits from
Egyptian geologists and government officials at our field camps located each season just east of quarry I. A general development of the period was our increasing
realization that fossiliferous lenses could be made much more productive by widespread removal of desert pavement.
Prior to 1977, microvertebrates in the lower sequence had been recovered with
regularity from only a single quarry (quarry E), which yielded the type of Oligopithecus savagei (Simons, 1962b). A major objective for 195‘7-79 was to identify
additional quarriable fossil sites for microvertebrates in the lower sequence. Because of low geographic relief and the uniformity of the sediments, microfossilbearing localities are difficult to identify by surface prosplecting. Nevertheless,
throughout the course of these three seasons, we identified and expanded four
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areas yielding small mammals the size of primates. These areas first began to
produce fossils in the 1979 season.
Quarry G is stratigraphically almost intermediate between the upper and lower
sequences. It is only about 16 meters above the barite sandstone placed by Bown
and Kraus (1988) at the base of the upper sequence, and lies about 66 meters below
the levels of quarries I and M. Quarry G was excavated extensively in the 1960s
and yielded a fauna with one primate and other mammals distinct from those
found elsewhere in the Fayum. The lithology of quarry G is quite different from the
other quarries in that it consists of a hardened salty sandstone rich in vertebrate
bones and teeth. In the course of further work a t quarry G in 1979 we discovered
a n additional quarry named V nearby which yielded larger and more complete
specimens from a stratigraphic level about 12 meters lower than G. These included
a complete creodont lower jaw and, in 1980, a n entire mandible of Propliopithecus.
Quarry V holds great potential for further finds of fossil primates and other mammals that lived at a time intermediate between the better-known faunas of the
lower and upper sequences.
Also in the late 1970s a series of pelvic or innominate bones that could be
assigned to Apidium phiomense and Parapithecus grungeri were found in quarry I
and described by Fleagle and Simons (1979). These Apidium pelves indicated a
small quadrupedal climbing and leaping form presumably capable of running and
jumping much as in Suimiri. Not all features of the innominate are like cebids.
There is a distinct iliac plane not found in New World monkeys and the ischium is
particularly long relative to the length from the acetabulum to the sacroiliac joint.
There is no trace of ischial callosities. Fleagle and Simons (1979) agreed with
Conroy (1976a) that the closest adaptive similarities of the postcranium in parapithecids lie among ceboid monkeys. Nevertheless, many differences in dental
and postcranial details suggest that this resemblance is only adaptive, not phyletic.
The much enlarged sample of upper and lower jaws and isolated teeth of Aegyptopithecus and Propliopithecus species found between 1977 and 1979 made possible
the taxonomic revision of Kay et al. (1981). When only the two types were known
Gingerich (1978) suggested that Aeolopithecus chirobates might tentatively be
considered as a male OfPropliopithecus haeckeli. Then in Szalay and Delson (1979)
both Aeolopithecus and Aegyptopithecus were referred to Propliopithecus. This referral was made without substantiation or careful study of the relevant specimens.
From about 1979 we recognized that Aeolopithecus should be referred to Propliopithecus and after that was discussed as Propliopithecus chirobates (as for example
Fleagle et al., 1980). A formal synonymy was presented in Kay et al. (1981). After
this revision it was clear that all the propliopithecid material from quarries I and
M was assigned to one of two species, Aegyptopithecus zeuxis and Propliopithecus
(= Aeolopithecus) chirobates. Aegyptopithecus zeuxis is the largest primate species
from the Fayum and was comparable in size to a howling monkey. Aegyptopithecus
zeuxis is distinguishable by having small incisors, narrow molar crowns with sloping sides, large and broad P4, and a dramatic size progression from M, to M,.
Aegyptopithecus zeuxis is sexually dimorphic in canine and premolar size and jaw
depth. Numerous finds demonstrated that “Aeolopithecus” chirobates, previously
known only from a single wind-eroded specimen, should be referred to Propliopithecus, which is considered a n advanced species occurring only in the upper
sequence quarries. This species, Propliopithecus chirobates, is reco nized by its
relatively broader, lower incisors and its steep-sided molar crowns. P5IS small and
narrow compared with M’; all three lower molars are subequal in length. Like
Aegyptopithecus zeuxis, Propliopithecus chirobates is sexually dimorphic in canine,
anterior premolar, and mandibular size. Kay et al. (1981) also considered that
Propliopithecus chirobates is a larger and presumably younger relative of Propliopithecus haeckeli, and that the type of Moeripithecus markgrafi has no distinctive
generic features. In order to deal with it, we ranked it as a separate species of
Propliopithecus. In proper modern practice, no such type containing only one or two
Simons]
EGYPTIAN OLIGOCENE PRIMATES
221
teeth, unless they are highly diagnostic (and these are not,), should ever be placed
in a separate genus.
Because there were so many new propliopithecid finds this allowed study of
sexual dimorphism in Apidium phiomense, Aegyptopithecus zeuxis, and Propliopithecus chirobates (Fleagle et al., 1980). Measurements of the canines of all three
species show a bimodal plot indicative of canine sexual dimorphism. Besides showing canine dimorphism Aegyptopithecus zemis and Apidium phiomense provide
evidence of dimorphism in the depth of the mandibular corpus. Jaw depth variation could not be determined for the two other contemporary species, Parapithecus
grangeri and Propliopithecus chirobates, as the number of well preserved jaws was
insufficient for statistical comparison. We inferred in this research that the three
species analyzed were more dimorphic than living monogamous primates and suggested that all of these three species lived in polygamous groups, presumably
characterized by male-male competition. We considered that this meant that extended interindividual contact in small family groups could date from this period
in our ancestry or before. Selection must also have favored recognition of the
multiple members of the larger group as individuals. In Fleagle et al. (1981) a
response was made to some criticisms put forward by Leuteriegger (1981)about our
conclusions regarding the demonstrable sexual dimorphism of early anthropoids.
Jungers et al., (1982) use allometric regressions derived from 454 adult catarrhines as a base with which to compare the limbs of fossil catarrhines. In order to
avoid circular reasoning, body mass of the fossils was not dlerived from limb-bone
measures. Rather, body mass for Aegyptopithecus and Apidium was derived from
regressions of tooth size and body size in living primates. This study showed that
Apidium phiomense possessed limbs much shorter than would be predicted for a
living catarrhine of its estimated biomass, with proportions imore like small-bodied
platyrrhines. According to Fleagle and Kay (1987)Apidium is neither a catarrhine
nor a platyrrhine. Likewise, Aegyptopithecus had an unusually short forelimb. We
concluded that (Jungers et al., 1982 p. 200) “among extant species of comparable
size, Macaca fascicularis approaches the condition seen in Aegyptopithecus more
closely than does Alouatta.”
As work proceeded into the 1980s, the discovery of fossils; continued to accelerate. At this point, many parallel lines of research had developed. For the purposes
of this review, key developments during this time are discussed under a series of
subheadings.
Cranial anatomy: Propliopithecidae
Several partial faces or skulls ofAegyptopithecusfrom quarry M turned up in the
1980s and were figured in Simons 1984. The first face was found in 1981, two more
recovered in 1982, a second and third skull in 1985 and 1986, and a fourth face in
1988. In combination, these all provided valuable additions to knowledge of cranial
anatomy in Aegyptopithecus. Most of them were described in detail in Simons
(1987).
The facial remains of Aegyptopithecus discussed in Simons (1987) were compared
with the face and remaining cranium of the original Aegyptopithecus skull located
in 1966 (see also Simons, 1984). It seems clear that the facial architecture of
Aegyptopithecus more nearly resembles that of later Miocene to Holocene apes
than it does that of modern cercopithecoid monkeys. The morphological relationships to monkeys, however, will be clarified with the description of a skull of
Victoriapithecus found in Kenya in the summer of 1994. The 1981 face of Aegyptopithecus is that of an old male quite different from the young male skull recovered in 1966. The face of this older male appears to be deeper, shorter, and looks
more like those of later Tertiary hominoids than does the 1966 find. Notable is the
location of the anterior temporal ridges, which converged ,just above the brow
ridges, an age-related phenomenon. Surprisingly, the two new faces discovered in
1982 are dissimilar to each other and to the other two as well; yet all four show the
characteristic Aegyptopithecus molar structure. A high degree of individual vari-
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ation is indicated, particularly since very large canines or canine sockets strongly
suggest that all four faces are from males. Leakey e t al. (1991) compared facial
anatomy of Aegyptopithecus with that of Afropithecus turkanensis from the Miocene of Kenya and these authors were able to show that the variation in the
Aegyptopithecus finds was consistent with differences in age of one species and th a t
Aegyptopithecus and Afropithecus shared a complex of primitive facial features
retained across about 17 million years. Simons and Rasmussen (1989) described in
detail the anatomy of the ear region of Aegyptopithecus and concluded that there
is little there or elsewhere in the skull that indicates shared-derived similarity
between i t and Tarsius.
Harrison (1987) suggested that Aegyptopithecus might not be near the common
ancestry of Old World monkeys and apes, postulating that they had a short-faced
common ancestor and citing the long-snout of the 1966 skull as being too primitive.
The new faces of Aegyptopithecus collectively indicate a much shorter faced animal. In addition, the new cranial remains of the oldest Miocene monkey, Victoriapithecus, recently reported by Benefit and McCrossin (1991 and personal communication) have an equally prominent rostrum.
Cranial anatomy: Parapithecidae
During the 1980s little was published about the cranial anatomy of the parapithecids; however, finds were made that suggested, but did not prove, that the
original Fayum frontal described by Simons (1959) probably belonged to Apidium.
Frontal and parietal fragments were also discovered in this period a t quarry I that
could be attributed to Parapithecus. Cartmill et al. (1981)discussed three isolated
petrosals from quarry I in the upper sequence which were presumed to belong to
Apidium. Both these authors and Gingerich (1973) noted the absence of a stapedial
branch of the carotid canal, an anthropoidean condition. Cartmill et al. showed
also that a squamosal reported by Gingerich as part of YPM 23968, thought by
Simons to be associated Apidium cranial parts, was not of a primate. It showed a
free intrabullar ectotympanic. No specimen yet found and definitely confirmed as
Apidium actually shows the position of the ectotympanic but pending proof to the
contrary the referred isolated petrosals discussed by Cartmill et al. indicate a
simple annulus a t the auditory aperture as in the platyrrhines and in early catarrhines such a s Catopithccus and Aegyptopithecus. The 1959 Apidium frontal, together with the best maxilla and mandible, make possible a hypothetical cranial
reconstruction (Fig. 6).
Skeletal anatomy: Propliopithecidae
Prior to finds of 1977, the postcranial anatomy of the Fayum propliopithecids
could only be deduced from the evidence provided by one ulna, a hallucial metatarsal, and one phalanx (see Fleagle et al., 1975; Preuschoft, 1974; and Conroy,
1976b). By the end of the 1970s the sample of various long bones belonging to
Aegyptopithecus and Propliopithecus was much expanded. These finds included
four partial humeri of Aegyptopithecus (Fleagle and Simons, 1978). Later field
seasons disclosed further propliopithecid limb bones, including a n ulna, a partial
tibia, and several calcanei attributable to Propliopithecus chirobates, as well as (in
1980) two complete humeri, a metacarpal, and phalanges of Aegyptopithecus
zeuxis.
Two complete Aegyptopithecus zeuxis humeri found in 1980 were described in
detail by Fleagle and Simons (1982a). These two humeri of Aegyptopithecus zeuxis
are a left humerus from quarry M and a right from quarry I. As we have seen, these
two quarries are appropriately the same stratigraphic level and also are the only
known sites which yield Aegyptopithecus zeuxis. They were allocated to this species
on grounds of compatible size and essential identity of the distal articular regions
with those distal humeral fragments of Aegyptopithecus and Propliopithecus that
had already been described by Fleagle and Simons (1978).
Like skeletal elements of Aegyptopithecus zeuxis described earlier these humeri
Simons]
EGYPTIAN OLIGOCENE PRIMATES
223
Fig. 6. The two best known parapithecids. Left: Three-quarters facial view of Apidium phiomense,
composite reconstruction of separate frontal, maxilla, and mandible. Right:Composite reconstruction of
the skull of Purupithecus grangeri. Associated facial and frontal fragments combined with separately
found parietal and mandible. Loss of lower incisors and great reduction of the uppers give this animal an
unusually short rostrum. Reproduced with permission of the American Museum of Natural History.
substantiate a locomotor resemblance to the platyrrhine monkey Alouatta. Fleagle
and Simons (1978)present detailed but schematic reconstructions of humeral muscle attachments. The 1980 analysis of total humeral morphology and presumed
muscular relationships further substantiated our earlier conclusion that Aegyptopithecus zeuxis was a robust and relatively slow moving arboreal quadruped.
Although the distal humeral articular region in Aegyptqpithecus resembles both
those of the Miocene hominoid Pliopithecus vindobonensis and those of several
living ceboid monkeys, the more proximal portions showed many prosimian-like
features not seen in living Anthropoidea. In these features of the humerus Aegyptopithecus zeuxis forms a connecting morphological intermediate between early
Tertiary primates and Miocene hominoids, just as do various details of the cranial
anatomy of Aegyptopithecus. Both cranial and postcranial morphology of this species are informative for delineating the course of higher primate evolution, specifically in establishing a stage of arboreal quadrupedalism near the base of the
catarrhine radiation. This overall adaptation differs from that of Adapis, which
seems to be a lorisine-like slow climbing quadruped (Dagosto, 1983) or that in
Notharctus, which is a n acrobatic leaper. Neither are any of these locomotor styles
particularly close to that inferred for Eocene omomyids. Perhaps the locomotor
system of Aegyptopithecus shows more about the basal catarrhine adaptation than
about basal anthropoidean lifestyles.
Forelimb function in Aegyptopithecus seems to have been rather like th a t of both
Varecia and Alouatta among extant forms. The broad brachialis flange, together
with a proximal origin of the brachioradialis muscle, suggests powerful flexors of
the arm. This condition is unlike that seen in the forearm1 of modern cercopithecoids. It presumably resembles a general primitive condition found in early primate quadrupeds that were well adapted to climbing but not yet particularly
adjusted to the more cursorial habits of most present-day cercopithecoids. Among
the East African Miocene apes the distal articular region in Aegyptopithecus zeuxis
is most similar to that of Proconsul and Dendropithecus, as well as to that of
various platyrrhines. Nevertheless, Dendropithecus has a straight humeral shaft
not proximally retrof lexed as in Proconsul. This conformation, differing from any
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YEARBOOK OF PHYSICAL ANTHROPOLOGY
[Vol. 38, 1995
ptopithecus zeuxis
Fig. 7. Postcranial elements of Aegyptopithecus entered in black. Although less complete than the
known postcranium of Apidiurn the skull is more completely known. Compared to many incompletely
known Miocene anthropoids, in Aegyptopithecus most of the major limb bones are represented but have
been recovered differentially. For instance, there are more than 18 partial or complete humeri but only
one partial innominate and parts of three femora. The propliopithecid tibia is represented only by a
single example from Propliopithecus chzrobates.
other Miocene ape humerus, suggests the acquisition of suspensory habits. Both
Proconsul and Dendropithecus are more advanced in humeral anatomy than Aegyptopithecus and Pliopithecus in having lost the entepicondylar foramen, still
present in some cebids and even as a rare anomaly in Homo sapiens. Senut reports
(personal communication) that the East African Miocene collections in Nairobi
contain at least one specimen KNM RU 5648 (Proconsul?) in which this foramen
is retained. Because there are few, if any, shared-derived anatomical features
which especially link Aegyptopithecus forelimb anatomy with hominoids rather
than with cercopithecoids, it may prove that both these Old World superfamilies
are derived from a forelimb plan like that of Aegyptopithecus. Interestingly, the
distal hind limb of Propliopithecus and what is known of the foot bones of Propliopithecus and Aegyptopithecus seem more progressive or derived than does the
humeral region of either. The talus and calcaneus of Aegyptopithecus all are close
morphologically to those of atelines and of Proconsul (Gebo, 1993). In turn, the foot
and hind limb of Proconsul show some resemblance to those of Pan according to
Walker and Pickford (1983). Figure 7 illustrates the principal skeletal parts now
known for Aegyptopithecus.
The broadening of the humeral trochlea as well as morphological details of the
distal condyles of Aegyptopithecus make good structural antecedent for distal humeral anatomy as observed in the East African Miocene apes. Although we suggest
(Fleagle and Simons, 1982a)that the hominoid-like teeth and humeral morphology
of Aegyptopithecus zeuxis might also have given rise to the non-hominoid dental
and postcranial features of the Miocene to recent Cercopithecoidea, this remains to
be proven by the discovery of actual fossil intermediates. Aegyptopithecus and
Simons]
EGYPTIAN OLIGOCENE PRIMATES
225
Propliopithecus have been called “dawn apes,” not “dawn” catarrhines, and this is
because of what may be shared primitive resemblances in teeth and facial anatomy
with later dryopithecine anthropoideans.
Fleagle and Simons (1982b) interpret new skeletal material of Propliopithecus
chirobates from the upper sequence sites as belonging to an early catarrhine with
a body mass only about two-thirds as large as estimates for Aegyptopithecus zeuxis.
Apart from their considerably smaller size, the partiad ulna and humerus of
Propliopithecus chirobates described in Fleagle and Simons (1982b) differ little
from these bones in Aegyptopithecus zeuxis (see Fleagle and Simons, 1982a). The
anterior middle part of the humeral shaft appears more rounded and less laterally
compressed than in Aegyptopithecus zeuxis and is thus a bit more like that in the
extant anthropoids. The ulna is probably more slender than in Aegyptopithecus
zezmis. The locomotor lifestyle which these bones strongly suggest is that of an
arboreal quadruped adept at climbing while adaptations for suspension, rapid
branch running, or terrestrial quadrupedalism are absent.
The left tibia of Propliopithecus chirobates described in Fleagle and Simons
(1982b) was then the only nearly complete long bone from the hind limb of a
Fayum propliopithecid. It shows a set of adaptive functions for the hind limb of
Propliopithecus quite different from those movements indicated by tibiae which we
elsewhere (Fleagle and Simons, 1983)allocate to Apidium phiomense. The Propliopithecus tibia is definitely short compared with those of any living primate species
that have dental and mandibular dimensions in the range of those of Propliopithecus chirobates. This shortness can be interpreted as being a primitive feature that
perhaps correlates best either with an early sort of arboreal quadrupedalism and
with climbing as in the apes. Because P. chirobates is a smaller animal the distal
articular facet is much smaller but is otherwise appropriate in form to articulate
with a talus attributed to Aegyptopithecus zeuxis by Fleagle (1983). The Propliopithecus chirobates tibia, overall, looks like a less long (or more “robust”) variant
of the tibiae belonging to the Miocene ape PZiopithecus uindobonensis. The later
species had, however, many more structural features throughout the skeleton that
suggest a greater development of suspensory abilities than the former. The distal
tibia1 articulation of Propliopithecus chirobates very closely resembles the same
articulation in Pliopithecus as well as that on the tibia of East African early
Miocene apes.
Four attributed calcanei from quarry I are both large and distinctly different
morphologically from the numerous calcanei found a t this same locality which
have been assigned to Apidium phiomense. The Propliopithecus chirobates calcaneus has a tuberosity which is comparatively both short and deep. Such a tuberosity is indicative of arboreal quadrupedal or suspensory forms such as Ateles,
Alouatta, the gibbons, or great apes, and is not like the longer, shallower tuberosity of more rapid runners (Papio, Cebus) or leapers (Pithecia, Saimiri) (see Fleagle and Simons, 1982b).
The subtalar facet of the Propliopithecus calcaneus extends posteriorly as in
living apes or as in Ateles and Alouatta. In contrast, the same facet in Apidium
phiomense and modern cercopithecoids is small and restiricted. Features of the
anterior neck and cuboid articulation both suggest a capacity for extensive rotation a t the transverse tarsal joint (Fleagle and Simons, 3982b). This rotational
capacity is presumably in correlation with a large grasping hallux (Preuschoft,
1974) and a foot very similar to that of Pliopithecus and Proconsul, but very differently structured to that of Apidium (see Conroy, 1976a).
Skeletal anatomy: Parapithecidae
Study of the postcranial anatomy of the Fayum parapithecids, Parapithecus and
Apidium, has been advanced by publication of a series of papers (Conroy, 1976a;
Fleagle and Simons, 1979; Fleagle, 1980; Fleagle and Simons, 1983; Anapol, 1983).
Most recently, Fleagle and Simons (1995) have contributed an extensive review of
the parapithecid skeleton based on the extraordinarily large sample of known
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[Vol. 38, 1995
skeletal parts of Apidium phiomense. As mentioned, Fayum propliopithecid bones
can easily be distinguished from Fayum parapithecid bones on anatomical grounds
in all cases and nearly always on the basis of absolute size as well. Almost all the
parapithecid skeletal parts come from quarry I where both Apidium phiomense
and Parapithecus grungeri occur. These two contemporaries differ in size and, quite
markedly, in dental anatomy. Nevertheless, there are no easily demonstrated differences in postcranial anatomy between these two parapithecids that have been
published so far. Apidium phiomense is much the more common species and authors have treated the majority of parapithecid skeletal parts as being of this
species. Conroy (1976a) discusses humeri, ulnae, radii, tali, and calcanei of Apidiu m from quarry I. For him, these bones indicated an animal locomoting as a small
arboreal quadruped, more lightly built than Aegyptopithecus, and perhaps resembling most closely modern Saimiri or Cebus.
Anapol(1983) has described an attributed partial scapula of Apidium phiomense
from quarry I. He found morphometric features that often approximated colobine
monkeys. Many shape features such as conformation of glenoid fossa and maxillary border are remarkably like Saimiri. Anapol concluded that: “Apidium phiomense is thus characterized as an arboreal quadruped with a locomotor repertoire
that includes a considerable amount of leaping and the use of forelimbs for clinging
and/or suspending during landing.”
Few associations of several skeletal elements from a single individual mammal
have ever been found in the Fayum (see Simons, 1968). One of these associations,
discovered in 1980, is attributed to Apidium phiomense and consists of a right
partial tibia and fibula, calcaneus, talus, and navicular, DPC 1303. This specimen,
as well as other hind limb bones of Apidium, was analyzed in Fleagle and Simons
(1983). Most remarkable is that the find demonstrates an extensive distal tibiofibular articulation or apposition. The distal tibio-fibular articulation or syndesmosis is found in Microcebus, other lemurs, and various platyrrhine monkeys, but
is not as developed as in Apidium. Of course, in Tarsius, the tibia and fibula are
fused distally. If this distal syndesmosis, perhaps misleadingly termed “incipient
fusion” by Fleagle, is seen as a primitive, or primitive anthropoid condition then
the more separate, or separated, tibia and fibula of all later catarrhines and most
large platyrrhines stand as the “advanced” or derived pattern. Since a stabilized or
co-ossified distal tibia and fibula occurs in tarsiers, some lemurs, and some platyrrhines, and now is demonstrated in Apidium, this feature must be either one that
has arisen repeatedly or a primitive retention. Its common possession between
platyrrhines and Apidium can hardly be sustained as a special link between these
two groups, as implied by Fleagle and Simons (1983). Both this articulation and
the way in which distal fibula and tibia articulate with spool-like and prominent,
subequal, parallel-sided trochlear ridges largely prevent rotational movements at
the tibio-talar joint. This sort of ankle seems also to characterize ankle structure
in certain omomyids. Figure 8 illustrates aspects of the skeleton in Apidium phiomense.
The associated talus and calcaneus of DPC 1303 confirm the correctness of the
allocation of other calcanei and tali to Apidium phiomense by Conroy (1976a).
Apart from the hinge-or-spool-likejoint with the tibia the talus is interesting in
showing a lengthened, medially directed neck which is indicative of a grasping
hallux. Unlike the elongated and posteriorly extended subtalar facet of Fayum
hominoids this facet in Apidium phiomense is of small size, a resemblance to Old
World monkeys.
Taxonomy and phylogeny: Propliopithecidae
One new species, Propliopithecus ankeli, was discovered a t quarry V (Simons et
al., 1987). This species is important because it provides a close match to a fossil
dawn ape found in Oman (Thomas et al., 1991). The Omani dawn ape was erroneously identified as Moeripithecus-a generic name that was previously synono-
Simonsl
EGYPTIAN OLIGOCENE PRIMATES
227
Fig. 8. The postcranial skeleton of Apidium phiomense, the most completely known early anthropoidean. Only parts of hands and feet, ribs and many of the vertebrae are missing. A: The long syndesmosis
between distal tibia and fibula. B The reduction of the third trochanter-still present in Aegyptopithecus. C : The anteroposteriorly deep distal condyles of the femur. D: The entepicondylar foramen and a
humeral capitulum shorter than that of Aegyptopithecus.
mized with the senior generic name Propliopithecus (Kay e t al., 1981). The correlations between Fayum and Omani primates are discussed below.
Fleagle and Simons (198213) concluded that in the skeleton Fayum apes much
more closely resemble Miocene and living apes than cerlcopithecoid monkeys. It
could be possible t h a t Old World monkey and ape lineages had already separated
in Oligocene times (Simons, 1972). For this to be so, only a few skeletal features
now seen in both cercopithecoids and hominoids, but not in the propliopithecids,
need to have evolved in parallel since then, and these are all features which could
easily have done so. Such easy-to-modify features include further lengthening of
the already tubular ectotympanic of Aegyptopithecus, together with loss of entepicondylar foramen and facial foreshortening. Fleagle and Kay (1983) present the
case that those dental and skeletal features which Oligocene apes share with
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Miocene-recent apes may all be primitive features and therefore could have typified early ancestral cercopithecoids as well. Solution of this problem will not come
until we have better skeletal material of undoubted early Old World monkeys. The
oldest African monkey bones come from Maboko, Kenya, and are not particularly
like those of either Oligocene or early Miocene apes. Fleagle and Simons (1982b)
concluded that the Fayum propliopithecid bones collectively seem to demonstrate
two points: 1)hominoids never passed through a “cercopithecoid” grade anatomically, and 2) “the arboreal slow climbing adaptations of apes, particularly in the
hind limb, are very old features . . .” (p. 175). Fleagle and Kay (1983)stress the
view that Aegyptopithecus and Propliopithecus are so generalized t h a t they can be
regarded as “suitable phyletic ancestors for all later catarrhines.” For these authors the hominoid resemblances of propliopithecids are seen only in the dental
anatomy. For them, Propliopithecidae is regarded as lacking any obviously derived
features linking i t with a specific extant group of catarrhines. Simons (1983) presents a review of then-current knowledge of both parapithecids and propliopithecids. Both groups are demonstrated to be of higher primate status and to have been
diurnal, active arboreal animals, living in polygamous social groups.
Taxonomy and phylogeny: Parapithecidae
Simons and Kay (1983) described the new genus and species Qatrania wingi
from quarry E. This is perhaps the smallest Fayum primate, with a n estimated
body weight of about 300 grams, about a quarter the size of the talapoin monkey
(smallest living catarrhine), and only a third the estimated size of the small Apidium, Apidium moustafai. It is quite definitely a member of the Parapithecidae,
seemingly most closely allied to Parapithecus fraasi. The weak molar cresting of
the worn teeth in the type specimen suggests a possible frugivorous or even a
gum-eating diet. Simons and Kay (1983) suggest that the parapithecid group is not
clearly related to either the platyrrhines or monkeys which might represent a
sister group to the other anthropoideans.
Simons and Kay (1988) described new mandibles of Qatrania wingi from quarry
E as well as a partial upper molar. They also report on and describe a mandible of
a new species Qatrania fleaglei from the upper sequence quarry M. Qatrania appears to lack facet X and has the lateral protocristid directed medially, which
distances parapithecids from catarrhines. For these reasons, a s well a s for others
listed in Fleagle and Kay (1987), the parapithecids may be considered a sister
group to all other Anthropoidea.
Kay and Simons (1983) present evidence that Parapithecus fraasi lacked permanent lower incisors or alternatively retained only a single pair of milk incisors into
adulthood. They noted that this remarkable dental arrangement is unlike that of
any other primate. Simons (1986) described mandibles of Parapithecus grangeri
from the upper sequence quarries which demonstrate that lower incisors were
completely lost in adults of this species. Contact facets on the lower canines show
that the lower canines contacted each other a t the midline. It would seem that in
the older species Parapithecus fraasi, a pair of milk incisors was retained into
adulthood. Known specimens are inconclusive as to how long, if a t all, Parapithecus grangeri may have retained its milk incisors. This bizarre dental adaptation
alone excludes Parapithecus from the ancestry of all known later higher primates.
Taxonomy and phylogeny: Prosimians, Afrotarsius and an omomyid
Tarsiid primates were first documented in Africa by Simons and Bown (1985).
These authors described a specimen found a t quarry M in the upper sequence that
they named Afrotarsius chatrathi. This is a find that preserves the molar crowns of
only the three right lower molars. Further individuals of this species have not been
recovered. Subsequent to its description in which it was placed in the Tarsiidae
there followed suggestions that it may represent a possible sister group to the
remainder of Anthropoidea, as was suggested in Fleagle and Kay (1987) and by
Ginsburg and Mein (1987). This view has recently been restated somewhat differ-
Simons]
EGYPTIAN OLIGOCENE PRIMATES
229
ently by Kay and Williams (1994). Nevertheless, all those features of the Tarsius
dentition which separate its very primitive teeth from those of anthropoids (with
the possible exception of small lower-molar hypoconulidsj are to be seen in Afrotarsius, which has very high trigonids and blade-like crests on lower molar tooth
cusps. Neither Tarsius nor Afrotarsius show any tangible shared-derived dental
similarities with archaic anthropoids. We now know 1)th,at Eocene primates that
are very close to modern Tarsius existed in all the northern continents in the
Paleogene-for example, Tarsius or more probably a closely related genus has
recently been reported from the Chinese Eocene (Beard et al., 1994) and tarsierlike forms such as Pseudoloris (Europe) or Shoshonius (North America) have long
been known; 2) that tarsiers are derived from the omomyid group; and 3) that a
different genus, we believe assignable to the Omomyidae, occurs at Fayum quarry
E (Simons et al., 1987). The presence of tarsioids in the African Oligocene is not
surprising. Afrotarsius, of which we know so little, is certainly not the material to
consider when establishing a sister relationship between tlhe tarsier group and the
Anthropoidea (Kay and Williams, 1994). It is almost identical with modern Tarsius. Figure 9 compares Afrotarsius lower molars with the same teeth in the
present-day tarsier.
Ecological setting
During the 1980s there were many discoveries that enlarged understanding of
earliest anthropoidean primates. This knowledge came not only from primate fossils, but from the other fauna and flora and from geological data. These other
discoveries served to clarify our understanding of the environmental associations
and temporal position of these primates. Fayum collections also include geological
samples and plant fossils important to understanding the ancient Fayum environment. The unusually well preserved “trace” fossils of the Fayum are, as we have
seen, the most varied anywhere from a single nonmarine sequence and their significance has been summarized in a series of papers by Bown and others (see for
instance Bown et al., 1982; Bown, 1982; and literature summarized in Genise and
Bown, 1994). During the early 1980s the majority of the Fayum fossil mammal
sites (including all localities yielding primates) were tied into a measured stratigraphic section, thus establishing their temporal relationships (Bown and Kraus,
1988). From this period also many fossil birds of importance were discovered in the
Fayum primate quarries. These birds represented both new groups and the earliest
occurrences in Africa for several bird families. Their great.est significance in relation to the primates are as environmental indicators. Since many bird genera and
even species have changed relatively little since the Oligocene, several types of
birds that are good environmental indicators have been identified, and are reviewed and described in Rasmussen et al. (1987). Olson and Rasmussen (1986) had
a year earlier demonstrated th at almost all of these birds are water birds and
showed that the closest environmental correlations of the Oligocene Fayum birds
are with the avifauna of the wetter forested areas of Uganda.
The anatomically demonstrable arboreality of all the IFayum primate species
was challenged by Kortlandt (1980), who argued that the Fayum forest trees had
actually grown far to the south of their present-day sites and had floated down a n
ancestral Nile river. By mainly emphasizing preliminary and outdated paleobotanical publications of the 19th century, Kortlandt attempted to demonstrate that
in Oligocene times the Fayum was a dry, semi-arid grassland or sahel. Bown et al.
(1982) demonstrates that there is no geological or paleontological basis for Kortland’s conclusion. Bown and Kraus (1988) also make cleair that no proto-Nile or
“Ur-Nil” of the early authors ever existed and that the Fayum’s silicified treetrunks have not been transported over long distances. As Simons (1982) concludes:
Trace fossils, fossil plants, the fossil vertebrates as a whole, and both old and new
sedimentological and paleopedological evidence all combine to indicate that in
Oligocene times, the Fayum evidently was subtropical to tropical. Fossils were
buried on a low lying coastal plain where abundant tall trees, vines, and local
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Fig. 9. Comparison of Oligocene Afrotarsius chatruthi (above)and present day Tursius syrichtu (below). Electron microphotographs brought to same MI-M, length. Placement of all cusps and crests are
the same in these two primates.
mangroves grew. Soils were largely damp and seasonal fluctuations in rainfall
occurred. Thus, it is clear that all kinds of evidence put the earliest hominoid
ancestors in the tropical forest environment. In fact, the commonest fossil fruit
from the Jebel Qatrani Formation, Epipremnum (family Araceae), may well have
been eaten by Apidium and Aegyptopithecus alike. It is known that the fruits of
certain modern day Araceae are eaten by both macaque and man.
Research summary 1977 to 1989
The primate discoveries of the late 1970s and 198Os, whether of new species or
simply new material, still present their own problems of interpretation. Oligopithecus sauagei, Qatrania fleaglei, and Qatrania wingi are known only from incomplete half mandibles or isolated upper teeth; also there is but one similarly
Simonsl
EGYPTIAN OLIGOCENE PRIMATES
23 1
fragmentary specimen of Afrotarsius chatrathi. The types of two other apparently
distinctive species of Propliopithecus, P. haeckeli and P. markgrafi, are still the
only known specimens of their species. Isolated teeth at quarry G seem to indicate
that these latter two species lived before the times represented by the upper
Fayum localities, quarries I, M, P, and K, where the youngest African Oligocene
primates have been found. The two best known parapithecid species, Parapithecus
grangeri and Apidium phiomense, each have adaptive features which exclude their
having a direct ancestral relationship to any later catarrhlines or platyrrhines. The
adaptation of Apidium seems to have been as a n exclusively arboreal inhabitant of
the tangles of vines and bushes growing over or near water in a riparian habitat,
where springing and leaping were a t a premium. Model-n Callicebus and Cercopithecus talapoin live in a similar environment. Fleagle aind Simons (1995) provide
a detailed and lengthy review of the postcranial anatomy of the known Parapithecidae.
The remainder of all Oligocene Fayum dawn ape specimens belong to two
propliopithecid genera, Aegyptopithecus and Propliopithecus. As outlined by Simons (19821, the former of these stands as a good candidate for ancestry of East
African Miocene Proconsul and Afropithecus and, thus, of all later Hominoidea.
This conclusion remains sound in spite of attempts to suggest otherwise (Andrews,
1970; Harrison, 1987). Propliopithecus chirobates may be a side branch that led
nowhere or could have given rise to Miocene Limnopithecus, Dendropithecus, or
Pliopithecus. The Fayum propliopithecids which have been called “dawn apes” are
generalized arboreal quadrupeds which lack both suspensory and terrestrial adaptations.
EGYPTIAN PRIMATE STUDIES OF THE 2990s
During the 199Os, the main emphasis on field work has shifted to the important
late Eocene site quarry L-41. However, further Oligocene collections continue to
expand knowledge of the Oligocene primates. In addition, laboratory analyses
have addressed many important issues concerning the Fayum Oligocene primates.
Simons and Rasmussen (1991) dealt with the question of which genera from the
Fayum are valid. Although most authors have retained the monospecific genus
Aegyptopithecus, it was, without careful study, lumped by others into the genus
Propliopithecus. The results of this study by Simons and liasmussen were to demonstrate that Propliopithecus, with four valid species, is easily distinguished at the
generic level from Aegyptopithecus. Additionally, they point out that Parapithecus
grangeri cannot be shown to differ a t the generic level from the type and only
known specimen of Parapithecus fraasi. Nevertheless the species described as
Parapithecus grangeri was transferred to another genus (Kay and Williams, 1994).
The problem is that the original diagnosis of Simonsius only distinguished it from
Apidium-not from Parapithecus fraasi. Complete references for these discussions
are included in Simons and Rasmussen (1991). Simonsius was originally diagnosed
(Gingerich, 1978) using combined characters drawn from the type of P. fraasi and
from specimens of Apidium phiomense (these two taxa are clearly different genera); therefore Simonsius is a taxonomic chimaera and should not be continued a s
a generic name. Kay and Williams state: “The single fact that Simonsius [they
mean Parapithecus grangeri] lacks all lower incisors as an1 adult and Parapithecus
certainly had a t least one pair, and perhaps two, should warrant a taxonomic
distinctness of the two at the generic level.” However, thi:j purported difference is
not a fact. The holotype and only known specimen of P. fraasi cannot demonstrate
when the sole pair of milk incisors might be lost. As discussed above, this single
incisor pair of the type of P. fraasi are milk teeth that might have been lost had
that individual become older. The two P. grangeri individuals that provide evidence have worn cheek teeth, are therefore are older than the P. fraasi type, and
could have lost milk incisors as late as middle life also. What actually binds the
two species in the same genus, among other things, is the extraordinary fact that
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YEARBOOK OF PHYSICAL ANTHROPOLOGY
[Vol. 38, 1995
alone among all known living and fossil anthropoideans these two species have lost
adult incisors. Simonsius is not a valid genus available for one of these two species.
In the same year as Simons and Rasmussen (1991) was published, Thomas et al.
(1991) resurrected the genus Moeripithecus for material from Taqah in the Sultanate of Oman that closely resembles Propliopithecus ankeli from the Fayum.
With first revisers privilege, and because of the extreme inadequacy of the type
and only specimen of Moeripithecus markgrafi, Kay et al. (1981) sustained Simons’
(1967, 1972) earlier reference of Moeripithecus markgrafi to the genus Propliopithecus where it (and the Omani material) should remain. Only two teeth, lower
M, and M,, were preserved in this type specimen (M. markgrafi) and the individual
is subadult so that metrics on the surviving mandibular fragment are uncertain.
The first and second lower molars are almost certainly the most undiagnostic
molars that anthropoideans have and propliopithecids show an exceedingly generalized pattern in these teeth. It may have been an acceptable practice in 1911
when Schlosser described Moeripithecus to select as a specific and generic type
such an inadequate specimen, but not now. Thomas et al. (1991) state that the new
material from Oman “extended” the diagnoses of this genus, but this is exactly
what one should not do when sustaining a poorly founded genus, because the
“extension” changes the original concept of the genus that started out being inadequate in the first place. First revisers rankings are important and there is no
reason to change the referral of this species to Propliopithecus. In any case the
Omani material should be referred to Propliopithecus ankeli and this reference
emphasizes a probable faunal correlation that helps to date the Omani fauna to the
middle of the Fayum section.
Leakey et al. (1991) deal with the remarkable similarities that have been discovered to exist between the facial cranium and mandibles of Aegyptopithecus and
those of Afropithecus, named in Leakey and Leakey (1986). These similarities
provided the first striking indication of a strong link between a particular species
of Oligocene primate with a species of ape from the succeeding Miocene epoch.
Most of the features in common appear to be shared primitive facial features
retained by the Miocene species,Afropithecus turkanensis. Since there is a striking
size difference between these two genera, Afropithecus being more than twice as
large, the several shared similarities appear not to have been affected by relative
size. These authors note more than two dozen shared similarities between these
two genera and others could be added. On grounds of dental similarity, Proconsul
and Afropithecus are clearly related, and do not differ in the postcranium nearly as
much as they do in the facial cranium. Their interrelatedness, as well as the
general common features of all the East African Early Miocene apes, when taken
together with the special resemblance between Afropithecus and Aegyptopithecus,
gives credence to the probability that the latter lies somewhere near the base of the
Hominoidea.
Rasmussen and Simons (1992) review the paleobiology of the Oligopithecus
group, the oligopithecines. Inasmuch as the best known oligopithecine is Catopithecus from the late Eocene, the group will be discussed in much greater detail
in the forthcoming review of the Eocene primates of the Fayum. Oligopithecus
sauagei from quarry E is estimated to have a size of about 700-1,000 grams based
on allometric molar size regressions. The recovery and description of a lower molar
of Oligopithecus from Oman (reported by Thomas et al., 1988) constitutes the only
record of an oligopithecine outside the Fayum, but at that time Arabia was clearly
connected to mainland Africa. Associated plants and animals at quarry E and at
Taquah, Oman, indicate a well-watered forested environment for these early anthropoideans.
Kappelman et al. (1991)report new age determinations for the Eocene/Oligocene
sediments of the Fayum depression. These dates in large part are derived from
geomagnetic reversal stratigraphy studies carried out in the Fayum by Kappelman. His studies suggest that the upper sequence quarries (M,P,I, and J) lie within
Chron C13 with an age estimate of earliest Oligocene. Current age estimates for
Simons]
EGYPTIAN OLIGOCENE PRIMATES
233
Chron C13 are between 33.14 and 33.32 Ma (see Swisher (andProthero, 1990). The
oldest Fayum fossil primates come from locality L-41, which lies 47 meters above
the base of the Jebel Qatrani Formation and at this level the correlation is with
Chron C15r, which Swisher and Prothero date to 35.56-35.94 Ma. This is a late
Eocene age correlation and makes L-41 older than the assignment of the Omani
primates to Chron C13 (Thomas et al., 1989).
Simons (1993) discusses the surficial anatomy of the brain of Aegyptopithecus
zewcis based on endocasts of the skulls of this species found in 1985 and 1986.
These endocasts are compared with those reported much earlier by Radinsky
(1973), as well as being compared with endocranial molds of various catarrhines.
In the new material, especially in the best preserved mold of the brain of the
female (DPC 6642), the olfactory bulbs and cerebellar gyri are tucked further
under the body of the cerebrum than had been thought from the study of the
endocast of the 1966 specimen. Seen from the side, this latter endocast is almost
saddle-shaped, because of a depression anterior to the large and protruding primary visual cortex areas behind the lunate sulci. The degree of detectable sulci on
this brain mold is comparable to what can be seen on endocasts of Alouatta, Pithecia, and Aotes, but is clearly less complex. Compared to volume of the entire
cerebrum the frontal lobes appear to be relatively smaller than those of any modern anthropoidean, but are large relative to those of typical prosimians. Radinsky
(1973) plotted the endocranial versus foramen magnum area of 16 species of prosimians and 22 anthropoidean species. In this determination he found that the plot
for Aegyptopithecus fell within that of the anthropoideans and outside that of the
prosimians. Simons calculated the brain to body weight ratio for Aegyptopithecus
(DPC 6642) as being 1:22. Judging from upper molar size, this female had a weight
of approximately 6,000 grams (about 13 lbs.).
In 1994, a series of papers were published which deal primarily with fossils from
the Eocene locality L-41, and these are to be followed by a series of papers that
should come out in 1995. These papers dealing with Eocene primates are Simons
et al. (19941, Gebo et al. (19941, Simons (19941, Simons and Rasmussen (1994,
1995). Gebo (1993)reviews in some detail the postcranial anatomy and adaptations
of both parapithecids and propliopithecids. A final paper, Fleagle and Simons
(1995), provides a monographic review of the limb skeleton and locomotor adaptations of Apidium phiomense, early anthropoid from Egypt.
This paper points out that as a result of the extensive excavations at quarry I,
more is now known of the limb skeleton of Apidium phiom,ense than for almost any
other primate from Eocene, Oligocene, or Miocene deposits. Perhaps only in Notharctus, Smilodectes, Pliopithecus, and Proconsul do comparable or more complete
skeletal remains exist. A shortcoming is that the majority of the remains of Apidiu m phiomense were found as isolated bones, although one important association of
hind limb bones does exist. Nevertheless, the majority of Apidium specimens come
from quarry I, where more than 600 partial mandibles have been found. This
makes Apidium more than 10 times as common than any other quarry I primate
with which it could be confused. In fact, at that site there are only two other species
near its size range, which are Parapithecus grangeri an.d Propliopithecus chirobates. The latter is a catarrhine with strikingly different postcranial anatomy
(where known) and Parapithecus grangeri is distinctly larger and far less common
than Apidium phiomense. At quarry I, where these bones are found, not one jaw of
other rare small primates such as Qatrania fleaglei or Afrotarsius chatrathi has
ever been located. Consequently, the allocation of most of the quarry I bones to
Apidium phiomense seems secure.
The functional pattern exhibited by analysis of its limb skeleton strongly suggests that it represents the pattern of small quadrupedal monkeys that are markedly adapted for leaping. These leaping adaptations are implied by many structural features of femur, tibia, and fibula, as well as the pelvis. This adaptation is
also indicated by the proportions of the fore and hind limbls. Nevertheless, study of
the exact structure of the elbow and of the pelvis does not produce evidence that the
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[Vol. 38, 1995
TABLE 2 . Adaptive profiles of two Fayum Oligocene primates
Characteristics
Body size
Activity pattern
Diet
Locomotion
Aegyptopithecus zeuxis
ca. 6,700g
Diurnal
Primarily fruit with some leaves
Robust arboreal quadruped
Apidium phiomense
ca. 1,700 g
Diurnal
Fruit and seeds
Active arboreal runner and leaper
animal practiced clinging t o or leaping from vertical supports. Instead, its leaping
activities must habitually have been launched from what was essentially a quadrupedal, running posture.
As might be expected, the limb skeleton of Apidium reveals a combination of
characteristics that do not now occur in any one group of primates, but in several.
It appears that there are probably more similarities with living platyrrhines, particularly such as owl monkeys, squirrel monkeys, and some marmosets. There
seems to be no question that Apidium stands confirmed as an anthropoid primate
with the essential characteristics that are used to apply to the common noun
“monkey” with living groups. Even considered as monkeys, there is a series of
characters separating Apidium from both platyrrhine and catarrhine monkeys. A
number of these features are seen otherwise as being more typical of prosimians
than of higher primates (see Fleagle and Kay 1987; Ford, 1994), while other characters are unique (see Fleagle and Kay, 1987; Fleagle and Simons, 1995). Fleagle
and Kay (1987) also have argued that because of the many primitive or distinctive
characters, the parapithecids are the sister group of all other Anthropoidea. In
contrast, Gebo and Simons (1987) and Gebo (1989) found skeletal resemblances
between Apidium and catarrhine monkeys. The exact phylogenetic relationships
of the parapithecids in early anthropoid phylogeny can be better determined when
all known material, or even finds not yet made, have been thoroughly assessed.
Simons (1995) discusses a new partial cranium of Apidium phiomense found in
1989 at quarry I in the upper sequence and other cranial remains of parapithecids.
One of the cranial fragments discussed in this paper is assigned to a new species of
Apidium. The cranial characters discerned in the various specimens firmly establish the Parapithecidae as belonging with Anthropoidea. The original Fayum frontal fragment described by Simons (1959) has been confirmed through its similarity
to the frontal of the skull found in 1989. Table 2 contrasts adaptations in the most
complete of the Fayum primates.
Gebo (1993) concludes that there are three groups of morphological features
characterizing the postcranial anatomy of Apidium. These are 1)features of arboreal quadrupedality; 2) characters of frequently leaping primates; and 3) adaptations of frequent climbers. In the foot he notes that the distinctive shape of subtalar
and transverse tarsal joints mirrors that of the modern Old World monkeys, both
groups having the same sort of reduced foot mobility that still is capable of climbing and grasping yet also exhibits adaptations for terrestriality. Gebo posits that
Apidium may have had terrestrially adapted forbears that later had these adaptations overlain with leaping adaptations.
Writing on the postcranium of Aegyptopithecus Gebo (1993)reviews the forelimb
bones and also analyses the talus, calcaneus, metatarsals, and phalanges. He reports the presence of numerous features in both forelimb and foot indicating frequent climbing abilities not seen at all in the foot of Apidium. Various features of
the talus suggest some leaping capacities but distinctly less developed than in
Apidium. Hamrick et al. (1995) have demonstrated that the phalanges of Aegyptopithecus are highly curved with adaptations for grasping, much as in Alouatta,
whereas Apidium had straight Saimiri-like phalanges resembling those of modern
above-branch quadrupedal runners and leapers.
In the 1990s a variety of projects are now underway that will soon be published
about Fayum primates. These include papers on the cranial anatomy of Aegyptopithecus and Catopithecus, the first by Simons and Ankel and the second by Simons
Simonsl
EGYPTIAN OLIGOCENE PRIMATES
235
and Rasmussen. Kay and Simons are preparing a monograph on the parapithecids.
Maas and Simons are reviewing variation in the enamel microstructure of Fayum
anthropoideans. A study is nearing completion by Ankell-Simons, Chatrath, and
Fleagle on new femora and an ischium of Aegyptopithecus:.Teaford and Hobbs are
separately studying dental wear and postcranial anatoiny of Fayum primates.
Greenfield is writing up studies of the anterior teeth of Fayum primates, and
Gingerich, Fleagle, and Simons are preparing a paper on the sexual dimorphism in
Catopithecus.
CONCLUSIONS
It seems fair to state in conclusion, when combining Eocene and Oligocene sites,
which contain cercamoniine adapoids, omomyids, tarsiids, plesiopithecoids,
lorisoids, parapithecids, propliopithecids, and at least one other undescribed primate family, that nowhere else on earth in one small area is there such a diversity
of fossil primates.
As the study of Egyptian Oligocene primates has been traced one can see that a
whole chapter of primate history has opened up. What are the principal points that
this history teaches us? Apart from 1)the great diversity in the primates of the
African Paleogene, these studies show 2) that the earliest Oligocene ancestors of
the anthropoideans are quadrupedal, relatively small-brained creatures possessing a great many primitive characters, most of which are also seen in platyrrhines
and the lemurs; 3) the craniology of Aegyptopithecus shows little resemblance to
that of the omomyids or the tarsiers; 4)hind limb adaptations in parapithecids are
quite different from those of the contemporary propliopithecids, which implies a
considerable time since separation of these two families. Nevertheless, Gebo (1993)
states that forelimb adaptations in these two families are more similar in that they
share robust humerus and ulna with prominent crests and flanges. The postcranial
skeleton of Aegyptopithecus shows that the earliest well-known catarrhine is not a
vertical clinger and leaper, or a jumper, but a quadruped; 5 ) a number of characters
place Aegyptopithecus and Propliopithecus with the catairrhini and since parapithecids are seemingly neither catarrhine nor platyrrhine the existence of platyrrhines contemporary with these two families but occurring elsewhere is implied;
and 6) the dental anatomy of Aegyptopithecus and Oligopithecus, both propliopithecines, more closely resembles that of the notharctine and cercamoniine
adapoids than it does that of the tarsioids and omomyids.
The search for new levels bearing primate fossils, or additional sites in the Fayum
which might show different faunal components, as well as filling in knowledge of
the skeleton and cranial anatomy for the majority of the Fayum primate species,
is far from over. We look forward confidently to a series of exciting new discoveries.
ACKNOWLEDGMENTS
So many have participated in the field work that led to the recovery of Fayum
primates that there is not room to name them individually. From December 1960
our long and enjoyable association with the Geological Survey and Mining Authority of Egypt (EGSMA) has continued. During this period, we have pursued a
most important scientific cooperation, working together with 12 successive directors of this distinguished survey as well as a host of Egyptian field geologists and
staff from the Survey and Cairo Geological Museum. All these Egyptian colleagues
must be thanked for having contributed most generously toward the achievement
of the many advances in knowledge we now have made regarding African Oligocene and Eocene primates, the fauna associated with them, and their geological
setting. EGSMA will celebrate its 100th anniversary in March 1996.
I thank also the many colleagues from America and around the world who joined
us during the two dozen field seasons wherein the above reported fossils were
found. Illustrations are from a number of sources: Figures 1,7,and 8 are modified
from illustrations provided by John Fleagle; the photograph used in Figure 4B is
by Chester Tarka and that of Figure 5 by David Brill; Figure 6 is reproduced from
236
YEARBOOK OF PHYSICAL ANTHROPOLOGY
[Vol. 38, 1995
Simons (1995); Figure 9 was photographed by Leslie Eivest. I thank D. Tab Rasmussen, Thomas M. Bown, H.H. Covert, D.L. Gebo, and Friderun Ankel-Simons
for assistance with the manuscript. This project received long-term support
through many grants from the National Science Foundation-Divisions of Geology, Biological Research Resources, and Anthropology. Funds were also provided
by the Smithsonian Foreign Currency Program, the Boise Fund of Oxford University, by Gordon and Ann Getty, Margot Marsh, and Verna Simons.
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