Comparative anatomy of the carotid canal in the Miocene small-bodied catarrhine Pliobates cataloniae

The Miocene primate Pliobates is a pliopithecoid

The systematic status of the small-bodied catarrhine primate Pliobates cataloniae, from the Miocene (11.6 Ma) of Spain, is controversial because it displays a mosaic of primitive and derived features compared with extant hominoids (apes and humans). Cladistic analyses have recovered Pliobates as either a stem hominoid or as a pliopithecoid stem catarrhine (i.e., preceding the cercopithecoid-hominoid divergence). Here, we describe additional dental remains of P. cataloniae from another locality that display unambiguous synapomorphies of crouzeliid pliopithecoids. Our cladistic analyses support a close phylogenetic link with poorly-known small crouzeliids from Europe based on (cranio)dental characters but recover pliopithecoids as stem hominoids when postcranial characters are included. We conclude that Pliobates is a derived stem catarrhine that shows postcranial convergences with modern apes in the elbow and wrist joints-thus clarifying pliopithecoid evolution and illustrating the plausibility of independent acquisition of postcranial similarities between hylobatids and hominids.

Systematics of Miocene apes: State of the art of a neverending controversy

Hominoids diverged from cercopithecoids during the Oligocene in Afro-Arabia, initially radiating in that continent and subsequently dispersing into Eurasia. From the Late Miocene onward, the geographic range of hominoids progressively shrank, except for hominins, which dispersed out of Africa during the Pleistocene. Although the overall picture of hominoid evolution is clear based on available fossil evidence, many uncertainties persist regarding the phylogeny and paleobiogeography of Miocene apes (nonhominin hominoids), owing to their sparse record, pervasive homoplasy, and the decimated current diversity of this group. We review Miocene ape systematics and evolution by focusing on the most parsimonious cladograms published during the last decade. First, we provide a historical account of the progress made in Miocene ape phylogeny and paleobiogeography, report an updated classification of Miocene apes, and provide a list of Miocene ape species-locality occurrences together with an analysis of their paleobiodiversity dynamics. Second, we discuss various critical issues of Miocene ape phylogeny and paleobiogeography (hylobatid and crown hominid origins, plus the relationships of Oreopithecus) in the light of the highly divergent results obtained from cladistic analyses of craniodental and postcranial characters separately. We conclude that cladistic efforts to disentangle Miocene ape phylogeny are potentially biased by a long-branch attraction problem caused by the numerous postcranial similarities shared between hylobatids and hominids-despite the increasingly held view that they are likely homoplastic to a large extent, as illustrated by Sivapithecus and Pierolapithecus-and further aggravated by abundant missing data owing to incomplete preservation. Finally, we argue that-besides the recovery of additional fossils, the retrieval of paleoproteomic data, and a better integration between cladistics and geometric morphometrics-Miocene ape phylogenetics should take advantage of total-evidence (tip-dating) Bayesian methods of phylogenetic inference combining morphologic, molecular, and chronostratigraphic data. This would hopefully help ascertain whether hylobatid divergence was more basal than currently supported.

The earliest hylobatid from the Late Miocene of China

Yuanmoupithecus xiaoyuan, a small catarrhine from the Late Miocene of Yunnan in southern China, was initially suggested to be related to Miocene proconsuloids or dendropithecoids from East Africa, but subsequent reports indicated that it might be more closely related to hylobatids. Here, detailed comparisons of the material, including seven newly discovered teeth and a partial lower face of a juvenile individual, provide crucial evidence to help establish its phylogenetic relationships. Yuanmoupithecus exhibits a suite of synapomorphies that support a close phylogenetic relationship with extant hylobatids. Furthermore, based on the retention of several primitive features of the dentition, Yuanmoupithecus can be shown to be the sister taxon of crown hylobatids. The contention that Kapi ramnagarensis from the Middle Miocene of India might represent an earlier species of hylobatid is not supported here. Instead, Kapi is inferred to be a specialized pliopithecoid more closely related to Krishnapithecus krishnaii from the Late Miocene of India. Currently then, Yuanmoupithecus represents the earliest known definitively identified hylobatid and the only member of the clade predating the Pleistocene. It extends the fossil record of hylobatids back to 7-8 Ma and fills a critical gap in the evolutionary history of hominoids that has up until now remained elusive. Even so, molecular estimates of a divergence date of hylobatids from other hominoids at about 17-22 Ma signifies that there is still a substantial gap in the fossil record of more than 10 million years that needs to be filled in order to document the biogeographic origins and early evolution of hylobatids.