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 chrono- species 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 gen- eral absence of still living intermediates, and of continuous intergradations, between living species makes the task of the neo- taxonomist fairly easy. However, in paleon- tology, 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 evolu- tionary theory requires. Yet, the placing of such intermediates in the classical binom- ial nomenclatural system is well-nigh im- possible. This problem is not experienced by students of hominids alone: it is en- countered, too, by students of other well- studied 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. Al- though different workers have already as- cribed a diversity of epithets to these as yet incompletely described fossils - rang- ing from A. africanus, through A. afri- canus habilis, A. habilis, H . habilis to H . erectus habilis! - most are agreed that the habilis group of fossils represent an intermediate form between Australopithe- cus 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 fmmes 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 opera- tion, 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 oc- cupied 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 recogni- tion of bigeneric nomina to apply to such forms.

Rather than create a new genus between two previously-recognized genera, or some- what 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,

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 .

Australopithecus/Homo habilis

103

104 P. V. TOBIAS

At the species level, there are fossil hominids in Africa which partake of the features of both Homo erectus and Homo sapiens. While most workers classify the Broken Hill and Saldanha crania as mem- bers of a race or subspecies of H . sapiens - H. sapiens rhodesiensis - (Campbell, ’64), a few regard them as late-surviving members of H . erectus (e.g. Coon, ’ 6 3 ) . A bispeciik nomen might make the classifi- catory position clear. Thus, the Broken Hill and Saldanha crania might be classi- fied :

/ erectus \ rhodesiensis /

Homo ‘ sapiens or, simply,

Homo erectus/sapiens rhodesiensis

These difficulties are not confined to fossil hominids. My friend and colleague, Yves Coppens of Paris, has drawn my at- tention to some of the solutions proposed for the naming of proboscidean specimens showing intermediate features. For in- stance, a number of intermediates have been encountered between tooth forms characteristic of the four proboscidean genera, Serridentinus, Anancus, Tetralo- phodon and Synconolophus.

(1) The Austrian paleontologist, Sch- lesinger, has described teeth which are intermediate in form between those of Anancus and Tetralophodon. He could not decide between the two, and so he made a fraction, thus:

Anancus arvernensis Tetralophodon longirostris

Such a designation does not make clear whether the population represented is sup- posed to be a hybrid one, between the two genera and species; or whether it repre- sents a group phyletically intermediate be- tween the two genera and species; or sim- ply a mingling of two forms in the same population.

(2) Viret of Lyons described the tooth of a mastodon from Turkey, which re- sembled 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-

___. _-

ilis problem might have been Australo- pithecus hominoides!)

( 3 ) Father Bergounioux of Toulouse described a mastodon tooth from Portugal which partook of the features of both Ser- ridentinus and Anancus. His compromise was to create a new genus called Ser- ridanancus! The creation of a new genus or of a new species, as in the previous example, disguises, rather than highlights, the important relationship between the two known forms, to which the new fossil may provide the clue.

Another mammalian paleontologist, R. F. Ewer of Ghana, has supported my pro- posal in print (’67). She describes this “new and radical solution to the problem of the nomenclature of intermediate transi- tional fossils, which can be classified nei- ther in the same taxon as their more primi- tive ancestors nor yet together with their more advanced descendants” as “an excel- lent suggestion” which “would admirably meet the desideratum of a name which adequately mirrors its author’s opinion on the evolutionary status of the animal to wbich he applies it” (’67, p. 281). She pro- poses that the name be written on a single line with an oblique stroke ( / ) between the names of the two genera in such a bigeneric nomen. “This method,” she de- clares, “might be equally applicable in other groups and we may yet see the ap- pe arance of Notochoerus /Phacoc hoerus meadowsi or Elephas planifrons/meridi- Ionatis.p

Ewer goes on to sound a final word of caution:

“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 ap- plied only in cases where a true intermedi- ate 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 an excuse for failure to determine accurately the characteristics of the material available, nor yet as a con- venient shelf upon which to dump incertae sedis whose uncertainty arises from inade- quate material. Designed as an exact state- ment of systematic position, it must not be used as an approximation.” (op. cit., p. 281).

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This suggested modification to the Rules for the naming of intermediates is pro- posed 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.

Ewer, R. F. 1967 Professor Tobias’s new no- menclature. s. Afr. J. Sci., 63: 281.

Robinson, J. T. 1965 Homo %abilis’ and the australopithecines. Nature, London, 205: 121- 124.

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.

The taxonomy and phylogeny of the australopithecines. In: Taxonomy and Phy- logeny of Old World Primates, with References to the Origin of Man. B. Chiarelli, ed. Supple- ment to 1967 Volume of Rivista di Anthro- pologia.

1968