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Endocasts and meningeal vascular patterns.

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AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY 95:355-362 (1994)
Notes and Comments
Endocasts and Meningeal
Vascular Patterns
comparison of data derived directly from the
skull with what was preserved on the endocast. In most cases, the endocasts resulted
in a loss of information, or, worse, preserved
Michael K. Diamond
an incomplete and easily misinterpreted
pattern. As for the endocasts I examined
Department of Anatomy, Palmer College of
Chiropractic, Davenport, Iowa 52803
that were prepared by others, information
In a recent issue of the AJPA, Falk (1993) was frequently absent, ambiguous, or mispresented frequency distributions of leading when compared with data derived
meningeal groove patterns in great apes. directly from skulls of the same species or
From her data she concluded that the genera.
Each primate genus presents its own pemeningeal arteries of the middle cranial
culiar
problems in the interpretation of crafossa and the endocranial surface superior
nial
vascular
traces (Diamond, 1988:1&20,
to it (“middle braincase”) are mainly sup268-287,
335-353).
Most of these problems
plied from the orbit (via the ophthalmic artery) in Pongo, while Pan relies mainly on a are exacerbated through the use of ensupply from the infratemporal fossa (via the docasts. In the great apes there tends to be a
middle meningeal artery). The relative ex- lot of tunneling, especially around such crittent to which Gorilla relies on these two al- ical areas as the orbit and floor of the middle
ternative sources falls between the other cranial fossa (Fig. 1).The situation is partictwo genera. Falk believes that none of the ularly bad in Gorilla, where there is somegreat apes relies on the middle meningeal times extreme overgrowth of the internal table of bone that buries meningeal grooves. In
artery to the extent that humans do.
Pongo,
meningeal grooves running along the
Falk collected her data from latex enpetrosquamous
and petrosphenoid sutures
docasts. This is a highly questionable source
are
frequently
converted
into canals that
of information. An endocast is two steps
will,
perforce,
not
show
up
on
endocasts (see,
away from the circulatory pattern that one
1992,
Fig. 7). Pan
for
example,
Diamond,
hopes to reconstruct from it. It records a poshas
the
fewest
problems,
but
even in this
itive impression of the bony traces left by
genus
the
situation
around
the
orbit is
meningeal arteries and veins as well as
poorly
resolved
by
endocasts.
other blood vessels such as dural sinuses
Falk‘s data would be more tenable had she
and emissary veins. Endocasts are very good
physically
verified the intramural arterial
at reproducing vascular grooves, but these
pathways
that
she has chosen to reconstruct
are not the only kind of traces that blood
of endocasts. She could
solely
on
the
basis
vessels leave behind. Vessels also leave behave
used
sectioned
skulls and either shined
hind canals and foramina. Latex will preor injected a colored
a
light,
passed
a
bristle,
serve the very proximal part of an intramusolution
through
the
meningeal
canals and
ral vessel trace but will seldon reproduce its
foramina
before
initiating
the
casting
procefull course or consistently reveal the existdure.
The
course
and
connections
of
intraence or position of an exit point.
mural
vessel
traces
can
only
be
reliably
In the course of prior research (Diamond
1988,1991a) I prepared a number of homi- established by physically tracing them (Dianoid endocasts (17 human and one each of mond, 1988; 1991a). Without such a procePan, Gorilla, Pongo, and Hylobates). All of
these endocasts were taken from skulls that
were hemisected or that had their roof reReceived December 31,1993; accepted February 27,1994.
moved. I was thus able to make a qualitative
0 1994 WILEY-LISS, INC.
M.K.DIAMOND
356
mbn.
an
m a x . a.
Fig. 1. Depiction of the left lateral side of an endocast of Pun with the meningeal grooves (heavy black
lines) drawn in a somewhat simplified manner. Broken
lines indicate those meningeal grooves that are most
subject to being converted into canals in great apes. The
two sources of supply to the meningeal arteries of the
middle cranial fossa have been drawn in schematic fashion. Numbers 1, 2, and 3 indicate the three main
branches (or territories) that Falk (1993) considered in
her analysis: 1, lower temporal branch 2, sylvian
branch; 3, coronal branch. Abbreviations: ext. car. a.,
external carotid artery; int. car. a., internal carotid artery; max. a,, maxillary artery; men.-lac. anast.,
meningeal arteryfiacrimal artery anstomosis; mid. men.
a,, middle meningeal artery; oph. a,, ophthalmic artery;
trans. sin., transverse sinus sulcus; sig. sin., sigmoid
sinus sulcus.
dure it is often difficult to determine
whether a vessel re-enters the cranial cavity, exits the skull, or terminates in the
diploe. For example, grooves on an endocast
that appear to be emerging from the orbit
may actually be connected to the “anterior
branch” middle meningeal groove (and the
infratemporal fossa) via a canal running
through the sylvian crest of the parietal
bone. In other words, an apparent supply
from the ophthalmic artery might actually
be a supply from the maxillary artery (via
the middle meningeal).
Falk’s endocasts were independently
coded by a graduate assistant, and the two
sets of results were in close agreement.
However, this only proves that Falk’s
method of interpretation is transferrable t o
others. If a feature is hidden on an endo-
cast, it will be consistently invisible to all
observers.
Falk commits a t least one clear error of
interpretation on the Pongo endocast illustrated in her Figure 5. She believes it shows
evidence of an artery that emerged into the
middle cranial fossa through the postglenoid
foramen. She also mentions other Pongo endocasts with a similar pattern. I expect she
was led to this hypothesis by a failure to find
any evidence of a more typical orbital or infratemporal arterial entry. This failure
must be due t o the roofing over or tunneling
of arteries and not due to genuine absence
because her reconstruction is impossible. A
postglenoid artery has never been verified
in any placental mammal, either through
dissection or through the examination of
sectioned embryos (Wible, 1990). I have certainly never seen one in any of the placental
mammals I have dissected (Diamond,
1991a, 1992).The only mammals for which a
postglenoid artery is known are some marsupials, and the vein it accompanies is not
homologous with the postglenoid vein of placentals (Wible, 1990). Assuming that the
illustrated specimen does, in fact, preserve a
cast of the postglenoid foramen, a more
likely interpretation is that the endocast
reflects partial drainage of the petrosquamous sinus via the postglenoid vein.
The petrosquamous sinus and its accompanying meningeal artery run along the
petrosquamous suture in a common sulcus.
An endocast cannot discriminate between
the two vessels. The artery presumably gave
off an ascending branch to the cranial side
wall opposite the postglenoid foramen-a
coincidental relationship.
Any confidence one might place in endocasts is further eroded by the very poor
correspondence between Falk’s published
data and data that I previously collected
from the sectioned skulls of extant hominoids (see Diamond, 1988). While we each
asked different questions and coded our
data in different ways, there were some areas of overlap. From my original data, I was
able to extract the frequency with which
there was no communication between the
meningeal vessels of the middle cranial
fossa and the orbit. This would correspond to
357
NOTES AND COMMENTS
TABLE 1. Comparison of frequencies of meningeal groove patterns in hominoids'
Falk (1993)
Pan troglodytes
Gorilla
Diamond (previously unpublished)
Pongo
Pan troglodytes
~~
Sample size
Pattern'
A1
E (all ~ a t e g o r i e s ) ~
Unclassified
A1 1%)
E (76)
Unclassified (%)
'R
Gorilla _ Pongo_ Homo
~
_
R
R
R
R
B
R
B
R
B
R
20
37
17
31
6
13
44
37
45
100
2
12
2
-
_
4
23
10
1
21
78
10
60
8
54
41
41
0
35
9
0
80
20
20
20
11
44
4
_
_
3
-
7 1 2
7 1 0
-
1
0
_
39
32
-
_
_
17
0
-
_
0
15
0
62
27
2
23
51
1
21
78
samples consisting of only right hemicrania; B = samples consisting of both left and right hemicrania. with most individual specimens
therefore counted twice.
'A1 = complete supply to the middle cranial fossa from ophthalmic artery; E = complete supply to the middle cranial fossa from middle
meningeal artery.
'Specimens allocated to pattern E by Diamond include only those specimens in which there is no communication between the meningeal grooves
of the middle cranial fossa and the orbit.
=
an extreme example of Falks pattern E (exclusive supply from the middle meningeal
artery). I also recorded the frequency with
which there was no connection between the
meningeal vessels in the middle cranial
fossa and the infratemporal fossa. This
would correspond to Falk's pattern A1 (total
supply from the ophthalmic artery).
The frequencies are shown in Table 1.For
some species, the number of individuals
Falk studied was relatively small. As a result, her samples drawn from only one side
are subject to sampling error. Therefore, I
have reproduced her data from the right side
and both sides combined. Because I examined many more specimens than Falk, my
comparison sample consists only of right
hemicrania, except in a few cases where only
the left side of a specimen was accessible. I
had no data on Pan paniscus, so only samples of Pan troglodytes are compared.
In my sample, 9 specimens of Pan (20%)
n = 44)) 8 specimens of Gorilla (21%, n =
37), and 23 specimens of Pongo (51%,
n = 45) were unclassified due to connections
of the meningeal grooves to both the orbit
and the infratemporal fossa. Two additional
specimens of Gorilla (5%)were unclassified
due to there being no detectable connection
to either the orbit or the infratemporal fossa
(an anatomical impossibility).
I did not lump my unclassified specimens
into categories A2-A4 (dual supply to the
middle cranial fossa from both the oph-
thalmic and middle meningeal arteries) for
two reasons. First, the coding procedure I
employed does not adequately resolve these
patterns. Second, presence of an orbital
communication does not necessarily mean a
contribution t o the middle cranial fossa from
the orbit (a requirement of pattern A). Blood
could just as easily be going toward the orbit, depending on the details of the pattern.
Unlike Falk, I often found it difficult to
make a determination of blood flow direction in such specimens.
By the same reasoning, the percentages
listed under pattern E in my column represent mimimum values and consist only of
those specimens without any communication between the middle cranial fossa and
the orbit. The actual percentages of pattern
E are likely to be considerably higher. In
humans, for example, complete separation
of the middle cranial fossa from the orbit
is much less common than in the African
apes (humans are in fact much closer to orangutans in this regard; see below). Yet it is
clear that humans rely almost exclusively
on the middle meningeal artery to supply
the middle cranial fossa (Diamond, 1988,
1991b).
There are some marked discrepancies between Falk's data and mine. According to
my data, in Pan troglodytes pattern E is
much more frequent (80%vs. 54%).This figure is also much greater than Falk reports
for Pan paniscus (63%, n = 19, both sides
_
358
M.K. DIAMOND
combined). In Gorilla, pattern A1 is much
less frequent (11%vs. 39%)and pattern E is
much more frequent (62% vs. 32%) than
Falk reports. In Pongo, pattern A1 is much
more frequent (44%vs. 15%).The only point
on which our data seem to agree closely is
that Pan troglodytes has a low frequency of
pattern A1 (0%vs. 8%).
While my frequency percentages are quite
different, the general morphocline that Falk
constructed is supported. Pongo does rely on
the ophthalmic artery to a greater extent
than the other comparison species. While I
have no idea how frequent pattern E really
is in Pongo, it has t o be less than in any of
the other species given the high frequency of
pattern A l . Among the African apes, Gorilla
does indeed rely more heavily on the ophthalmic artery than Pan, albeit only slightly.
Given that Pan has a minimum, value of 80%
for Pattern E, I doubt that it is any less reliant
than humans on the middle meningeal artery
to supply the middle cranial fossa. However,if
encroachment into the orbit is also included,
humans may yet occupy the far end of the
pattern E morphocline.
To assess this possibility, I re-analyzed
data from a subsample of 100 right hemicrania drawn from two skeletal populations
that were reported on previously by Diamond (1988). Fifty skulls were from the University of Chicago’s Department of Anatomy
and presumably trace their origin to the Indian subcontinent. The other 50 were from
white Americans of both sexes drawn from
the Terry Collection of the U.S. National
Museum. Of these 100 hemicrania, 79%
showed an apparent communication between the orbit and the meningeal grooves
of the middle cranial fossa. Comparison percentages are 20% in Pan (n = 44), 33% in
Gorilla (n = 37), and 96%in Pongo (n = 45).
In all but one of the human hemicrania, the
meningeal grooves also communicated with
the infratemporal fossa through the foramen spinosum. Therefore, 78% could not be
classified as conclusively possessing either
pattern E or pattern A2-A4 (Table 1).
The 79%value for humans is quite close to
published data drawn from dissection studies of the human orbit and its collateral circulation. Ducasse et al. (1985) report that
83% of the orbits they dissected (n = 70)
showed anastomosis between the arteries of
the orbit and the middle cranial fossa. Hayreh (1962) reported a frequency percentage
of 85% (n = 59).
Despite the high frequency of arterial
communication between the orbit and middle cranial fossa, neither of these papers reported a single case of a supply to the middle
cranial fossa from the orbit, only the reverse. A supply to the middle cranial fossa
from the ophthalmic artery is unusual
enough that it is the subject of a substantial
number of case reports in the medical literature (e.g., McLennan et al., 1974; Dilenge
and Ascherl, 1979). In my own examination
of an expanded sample of 638 human hemicrania, only 17 (3%) showed unmistakable
evidence of a supply to the middle cranial
fossa from the ophthalmic artery (Diamond,
1991b).
The high frequency of arterial communication between the orbit and the middle cranial fossa may indicate that humans have
been extending the territory of the middle
meningeal artery into the orbit and thus expanding the boundaries of pattern E. Of the
dissection studies cited above, Ducasse et al.
(1985) reported that 27% of orbits (n = 70)
definitely showed some takeover by the middle meningeal artery (usually the lacrimal
branch of the ophthalmic artery), while
Hayreh (1962) implied that around 22% of
the orbits he examined (n = 59) showed
some degree of annexation by the middle
meningeal artery.
Australopithecines and pre-erectus Homo
appear to have a basically chimpanzee-like
pattern of meningeal grooves (Diamond,
1988). It would not be surprising if the similarity extended to a low frequency of communication between arteries of the orbit and
middle cranial fossa. One can speculate that
the re-establishment in later Homo of communication a t frequencies nearly as high as
Pongo would be a case of phenotypic similarity but functional disparity.
LITERATURE CITED
Diamond MK (1988) Cephalic Vascular Evolution and
Development in Primates: The Stapedial Artery and
NOTES AND COMMENTS
its Companion Venous Sinuses. Ph.D. dissertation,
University of Chicago. Ann Arbor: University Microfilms.
Diamond MK(1991a) Homologies of the stapedial artery
in humans, with a reconstruction of the primitive stapedial artery configuration of euprimates. Am. J.
Phys. Anthropol. 84:433-462.
Diamond MK (1991b) Homologies of the meningeal-orbital arteries of humans: A reappraisal. J . Anat. 178:
223-241.
Diamond MK (1992) Homology and evolution of the orbitotemporal venous sinuses of humans. Am. J. Phys.
Anthropol. 88:211-244.
Dilenge D, and Ascherl GF (1979) Variations of the ophthalmic and middle meningeal arteries. AJNR 1:
45-53.
Ducasse A, Segal A, Delattre JF, Burette A, and Flament J B (1985) La participation de l’artere
carotide externe a la vascularisation orbitaire. J . Fr.
Ophtalmol. 8r333-339.
Falk D (1993)Meningeal arterial patterns in great apes:
Implications for hominoid vascular evolution. Am. J.
Phys. Anthropol. 92:81-97.
Hayreh SS (1962) The ophthalmic artery. 111. Branches.
Br. J. Ophthalmal. 46:212-247.
McLennan JE, Rosenbaum AE, and Haughton VM
(1974) Internal carotid origins of the middle
meningeal artery. Neuroradiology 7:265-275,
Wible J R (1990) Petrosals of Late Cretaceous marsupials from North America and a cladistic analysis of the
petrosal in therian mammals. J Vert Paleont 10:183205.
Reply to Dr. Diamond
Dean Falk
Department of Anthropology, SUNY at
Albany, Albany New York 12222
I was pleased to read that in Dr. Diamonds Comments (Diamond, 1994), “the
general morphocline that Falk constructed
is supported”; yet I was surprised to read
that “data from latex endocasts. . . [are] a
highly questionable source of information.”
Until now, the only thing that has not been
controversial about primate endocranial
casts (endocasts) is the observation that
they clearly reproduce the meningeal vessels that course on the external surface of
the dura mater and are “grooved into the
internal surface of the braincase. In fact, it
is often easier to discern meningeal arteries
359
from veins on endocasts than in the cranium
alone because the smaller arteries stand out
on endocasts as “zigzag beading marks”
(Jones, 1912) that course on or near their
wider venous companions. Nevertheless, Diamond asserts that there are “peculiar problems” associated with interpreting meningeal patterns on ape endocasts because of
tunneling of meningeal vessels and their
tendency to be covered by (‘overgrowth of
the bony table, etc., and he therefore questions the accuracy of my observations of
meningeal arterial patterns on 100 hemispheres from pongid endocasts.
A possible explanation of these “peculiar
problems” is that Diamond has prepared
only one endocast (or hemicast; it is not clear
which) each from Pan, Gorilla, and Pongo
and compared them with their respective
skulls. Thus he is basing his generalization
of a lack of relationship between ape endocasts and their respective crania on sample sizes of one, a practice that is considered
statistically invalid. Diamond has also observed endocasts “prepared by others,” but
he does not specify their number nor species
nor say if he compared these endocasts with
their respective skulls. On page 351 of his
dissertation (Diamond, 19881, Diamond
states that he did a statistical study of 86
endocasts (hemicasts?) of Pan paniscus but
does not list any endocasts for the other
great apes. This is confusing because in the
present note he states that “I had no data on
Pan paniscus, so only samples of Pan troglodytes are compared.” This is discussed below.
With regard to the endocasts that I studied, I used a casting procedure that employed a thin liquid latex that cast foramina
including openings of bony canals (Fig. 1). I
had no need to “have used sectioned skulls
and either shined a light, passed a bristle, or
injected a colored solution through the
meningeal canals and foramina before initiating the casting procedure” (Diamond,
1994). With the endocasts that I used, there
were no “peculiar problems.” The eight pat-
Received March 28,1994; accepted April 20,1994.
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