The Phenetic Position of Pliopithecus and its Phylogenetic Relationship to the Hominoidea

Ciochon, R. L., and R. S. Corruccini (Department of Anthropology, University of California, Berkeley, CA 94720 and Division of Physical Anthropology, Smithsonian Institution, Washington, D.C. 20560) 1977. The phenetic position of Pliopithecus and its phylogenetic relationship to the Hominoidea. Syst. Zool. 26:290-299.-Problems of ascertaining affinities of fossil taxa are explored utilizing the European Miocene primate Pliopithecus vindobonensis as an example. Traditionally, Pliopithecus has been regarded as an ancestral gibbon, yet aspects of its postcranial anatomy contradict this. Current studies provide strong evidence that the forelimb complex of the extant Hominoidea represents a synapomorphic character complex. The shoulder joint of Pliopithecus was therefore compared with 17 species of anthropoid primates using 10 measurements emphasizing the glenohumeral articulation. Multivariate analysis indicates that Pliopithecus conforms in every way with the symplesiomorphic morphopattern shown by extant cercopithecoids and platyrrhine primates but contrasts markedly with extant hominoids, especially the gibbon. It is therefore unlikely that Pliopithecus and Hylobates are directly related. The great similarity of Pliopithecus to the African Miocene primate, Dendropithecus, also sheds doubt on its current hylobatine classification. [Phenetics; phylogenetics; shoulder; multivariate analysis; Pliopithecus.] The accurate assessment of the taxonomic and phylogenetic affinities of fossil taxa has always been a difficult task. Problems arise from inaccurately applied neontological systematics and the disparate usage of various taxonomic philosophies (Schaeffer, Hecht and Eldredge, 1972). The exact nature of the relationship of a particular fossil specimen to other fossil and recent taxa, be it phenetic, cladistic, evolutionary or otherwise, must be expressly stated. If not, misinterpretations may develop and later become the source of futile controversy. An appropriate example can be found in discussions of the European Miocene primate Pliopithecus vindobonensis. The first specimens allocated to the genus Pliopithecus were discovered as long ago as the early part of the middle 19th century (Lartet, 1837; Blainville, 1840; Gervais, 1845). Today, Pliopithecus ranks as perhaps the best known Neogene fossil primate, being represented by 3 partial skeletons and hundreds of isolated cranial and dental elements. Yet the phylogenetic affinities of this primate are still the subject of much recent speculation (Groves, 1972, 1974; Tuttle, 1972; Frisch, 1973; Simons and Fleagle, 1973; Morbeck, 1972, 1975; Feldesman, 1975; Delson, 1975, 1976; Delson and Andrews, 1975). When only dental remains of Pliopithecus were known, it was widely believed to be a small hominoid primate ancestral to the extant Hylobatinae (Lartet, 1837; Hiirzeler, 1954; Piveteau, 1957). Others who studied the dentition, however, did notice certain primitive features such as a strong buccal cingulum, frequent occurrence of a paraconid on M1, distal position of the metaconid, existence of a direct hypoconid-protoconid ridge and the tendency of the talonid to be broader than the trigonid (Ferembach, 1958; Remane, 1965; Groves, 1972). With the discovery of the 3 partial skeletons of Pliopithecus in the middle Miocene ("Vindobonian" or Badenian in current local terminology) deposits of Czechoslovakia, a reassessment of the genus took place. However, the outcome was very similar to the traditional long standing view (Zapfe, 1958, 1960; Simons, 1964, 1969) despite the presence of such primitive postcranial features as a low intermembral index, unspecialized hand pha-