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Bigeneric nomina A proposal for modification of the rules of nomenclature.

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BRIEF COMMUNICATION
Bigeneric Nomina : A ProposaI for Modification
of the Rules of Nomenclature
P.V. TOBIAS
University of the Witwatersrand, Johannesburg
ABSTRACT
It i s difficult to name fossils which are intermediate between chronospecies or chronogenera in general paleontology. A possible solution is proposed for
discussion: namely, to utilize bigeneTic nomina to designate a group of fossils which
are intermediate between two consecutive genera, and bispecific nomina to designate
fossils which are intermediate between two consecutive species.
Conventional and accepted taxonomic
procedure, as defined in the International
Rules of Zoological Nomenclature, is based
largely on neontological methods. The general absence of still living intermediates,
and of continuous intergradations, between
living species makes the task of the neotaxonomist fairly easy. However, in paleontology, vertical continuity of species
(chronospecies) in phyletic lines or clades
raises considerable taxonomic difficulties.
The richer the fossil record in any one
branch of living things, the more likely is
one to find intermediates -which evolutionary theory requires. Yet, the placing of
such intermediates in the classical binomial nomenclatural system is well-nigh impossible. This problem is not experienced
by students of hominids alone: it is encountered, too, by students of other wellstudied groups of mammals.
One such intermediate group of fossils
comprises Olduvai hominids 4, 6, 7 and
8 from Bed I and Olduvai hominids 13, 14
and perhaps 16 from Bed 11. This group
of fossils has been considered by some to
represent a separate taxon, H . habilis. Although different workers have already ascribed a diversity of epithets to these as
yet incompletely described fossils -ranging from A. africanus, through A. africanus habilis, A. habilis, H . habilis to H .
erectus habilis! -most are agreed that
the habilis group of fossils represent an
intermediate form between Australopithecus and H o m o (as previously recognized),
Granted that bigger samples confirm that
H o m o habilis is an intermediate form, how
are we to name such f m m e s de passage?
The very basis of our classificatory system
AM. J. PEPS. ANTHROP.,31: 103-106.
is evolutionary or phylogenetic. Yet when,
as at Olduvai, we have intermediate fossils
virtually representing evolution in operation, we find ironically enough that our
rules of nomenclature are not fully equal
to the task of naming such intermediates
(Tobias, '67, '68). For instance, although
its features indicate that H . habilis occupied a position intermediate between
Australopithecus and H o m o , the rules of
nomenclature require that if it be named
at all,it be assigned to one or other genus.
The rules do not permit a bigeneric nomen,
although such a name would probably most
faithfully reflect its systematic status. A
pIea might well be made for the recognition of bigeneric nomina to apply to such
forms.
Rather than create a new genus between
two previously-recognized genera, or somewhat arbitrarily place a taxon in one or
other genus, we might name such a form
as that represented by the habilis group of
fossils in the following manner:
Austrnlopithecus
Homo
\
/ habizis
or, for ease of typesetting, as Ewer ('67)
has suggested,
Australopithecus/Homo habilis
Such a bigeneric nomen would probably
portray the true systematic position of the
group of fossils more faithfully than if they
were placed in one or other genus, or, stiu
less, in a new genus; it avoids, too, the
difficulties created by Robinson's ('65)
proposal that, not only the habilis fossils,
but also Australopithecus africanus, be
taken into the genus H o m o .
103
104
P. V. TOBIAS
At the species level, there are fossil ilis problem might have been Australohominids in Africa which partake of the pithecus hominoides!)
( 3 ) Father Bergounioux of Toulouse
features of both Homo erectus and Homo
sapiens. While most workers classify the described a mastodon tooth from Portugal
Broken Hill and Saldanha crania as mem- which partook of the features of both Serbers of a race or subspecies of H . sapiens ridentinus and Anancus. His compromise
- H. sapiens rhodesiensis - (Campbell, was to create a new genus called Ser’64), a few regard them as late-surviving ridanancus! The creation of a new genus
members of H . erectus (e.g. Coon, ’ 6 3 ) . A or of a new species, as in the previous
bispeciik nomen might make the classifi- example, disguises, rather than highlights,
catory position clear. Thus, the Broken the important relationship between the two
Hill and Saldanha crania might be classi- known forms, to which the new fossil may
provide the clue.
fied :
Another mammalian paleontologist, R.
F.
Ewer of Ghana, has supported my proHomo / erectus \ rhodesiensis
posal in print (’67). She describes this
/
sapiens
“new and radical solution to the problem
or, simply,
of the nomenclature of intermediate transitional fossils, which can be classified neiHomo erectus/sapiens rhodesiensis
ther in the same taxon as their more primiThese difficulties are not confined to tive ancestors nor yet together with their
fossil hominids. My friend and colleague, more advanced descendants” as “an excelYves Coppens of Paris, has drawn my atlent suggestion” which “would admirably
tention to some of the solutions proposed
for the naming of proboscidean specimens meet the desideratum of a name which
showing intermediate features. For in- adequately mirrors its author’s opinion on
stance, a number of intermediates have the evolutionary status of the animal to
been encountered between tooth forms wbich he applies it” (’67, p. 281). She procharacteristic of the four proboscidean poses that the name be written on a single
genera, Serridentinus, Anancus, Tetralo- line with an oblique stroke ( / ) between
the names of the two genera in such a
phodon and Synconolophus.
(1) The Austrian paleontologist, Sch- bigeneric nomen. “This method,” she delesinger, has described teeth which are clares, “might be equally applicable in
intermediate in form between those of other groups and we may yet see the apAnancus and Tetralophodon. He could not pe arance of Notochoerus /Phacoc hoerus
decide between the two, and so he made meadowsi or Elephas planifrons/meridiIonatis.p
a fraction, thus:
Ewer goes on to sound a final word of
Anancus arvernensis
___. _caution:
Tetralophodon longirostris
‘
Such a designation does not make clear
whether the population represented is supposed to be a hybrid one, between the two
genera and species; or whether it represents a group phyletically intermediate between the two genera and species; or simply a mingling of two forms in the same
population.
( 2 ) Viret of Lyons described the tooth
of a mastodon from Turkey, which resembled both the teeth of Synconolophus
and of Senidentinus. His uncertainty was
resolved by his creating a new species
called Synconolophus serridentinoides! (An
equivalent compromise solution to the hab-
“Professor Tobias’s proposals will have no
practical value if the use of his system
is not rigorously restricted to the purpose
for which it was devised. It must be applied only in cases where a true intermediate position has been clearly established
-and
that between two taxa which are
so similar that the erection of a coequal
intermediate group is impossible. It must
not be used as a n excuse for failure to
determine accurately the characteristics of
the material available, nor yet as a convenient shelf upon which to dump incertae
sedis whose uncertainty arises from inadequate material. Designed a s an exact statement of systematic position, it must not
be used as a n approximation.” (op. cit.,
p. 281).
BIGENERIC NOMINA
This suggested modification to the Rules
for the naming of intermediates is proposed for the discussion and opinion of
my colleagues.
LITERATURE CITED
Campbell, B. 1964 Quantitative taxonomy and
human evolution, In: Classification and Human
Evolution. S. L. Washburn, ed. London,
Methuen & Co.
Coon, C. S. 1963 The Origin of Races. London,
Jonathan Cape.
105
Ewer, R. F. 1967 Professor Tobias’s new nomenclature. s. Afr. J. Sci., 63: 281.
Robinson, J. T. 1965 Homo %abilis’ and the
australopithecines. Nature, London, 205: 121124.
Tobias, P. V. 1967 General Questions Arising
from Some Lower and Middle Pleistocene
Hominids of the Olduvai Gorge, Tanzania. S.
Afr. J. Sci., 63: 41-48.
1968 The taxonomy and phylogeny of
the australopithecines. In: Taxonomy and Phylogeny of Old World Primates, with References
to the Origin of Man. B. Chiarelli, ed. Supplement to 1967 Volume of Rivista di Anthropologia.
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