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.