Evolutionary ecology of Miocene hominoid primates in Southeast Asia.

The evolutionary history and palaeoecology of orangutans remains poorly understood until today. The restricted geographic distribution of extant Pongo indicates specific ecological needs. However, it is not clear whether these needs were shared by the great diversity of fossil pongines known from the Miocene to the Pleistocene. Here we show how niche modelling of stable carbon and oxygen isotope data of the carbonate fraction of dental enamel can be used to reconstruct the paleoecology of fossil and modern pongines and associated mammal communities. We focus on Khoratpithecus ayeyarwadyensis, a Late Miocene pongine from Myanmar and the sister clade to extant orangutans, and compare it to its associated mammal fauna and other fossil and extant pongines. The results are consistent with a vertical position high up in the canopy of a forested habitat with purely C3 vegetation for K. ayeyarwadyensis as well as the contemporaneous Sivapithecus. Although their positions in the modelled isotopic niche space look similar to the ecological niche occupied by modern Pongo, a comparison of the modelled niches within the pongine clade revealed possible differences in the use of microhabitats by the Miocene apes.

Amphipithecine primates are stem anthropoids: cranial and postcranial evidence.

Since their discovery in 1927, the phylogenetic status of the Myanmar amphipithecines has been highly debated. These fossil primates are recognized either as anthropoids or as adapiform strepsirrhines. This uncertainty was largely the consequence of a limited fossil record consisting mostly of jaw fragments but lacking the critical cranial elements that might resolve this debate. We report here cranial remains associated with an ulna from a single individual pertaining to the amphipithecine Ganlea megacanina. In addition to anthropoid-like dentognathic characters, Ganlea displays several ulna and skull features that testify to its anthropoid affinities (e.g. short subvertically oriented lacrimal duct, lacrimal foramen and bone inside the orbit, maxillary contribution to the lower orbital rim, fused metopic suture). By contrast to crown anthropoids, however, Ganlea lacks postorbital closure, confirming that postorbital closure appeared later than many anthropoid dentognathic characters and evolved convergently in extant tarsiers and anthropoids. Thus, amphipithecines must now be recognized as stem anthropoids offering a unique window on the early evolution of cranial and skeletal features in anthropoids, and reinforcing the hypothesis of an origin and early diversification of anthropoids in Asia.

A new anthropoid from the latest middle Eocene of Pondaung, central Myanmar.

A new genus and species of medium-sized fossil primate, Myanmarpithecus yarshensis, is described from the lastest middle Eocene sediments of Pondaung, central Myanmar (Burma). The specimens consist of right maxillary fragments with P(4)-M(3)and a left mandibular corpus with C-P(3)and M(2-3). To date, three purported anthropoids have been discovered from the Pondaung Formation: Pondaungia and Amphipithecus (Amphipithecidae) and Bahinia (Eosimiidae). Myanmarpithecus differs from these other Pondaung primates in having cingular hypocones on upper molars and in lacking paraconids on M(2-3). Although Myanmarpithecus resembles some utahiin omomyines in superficial aspects of the morphology of M(2-3)(i.e., mesiodistally compressed molar trigonid and enamel crenulation), the morphological analysis of upper molars and lower premolars indicates that it is neither an omomyoid nor an adapoid but is more derived than fossil prosimians (such as adapoids, omomyoids, and tarsiers) and more anthropoid-like. On the other hand, it is more primitive (prosimian-like) than early anthropoids from the late Eocene/early Oligocene of the Fayum, Egypt. Myanmarpithecus is likely to be an early, primitive anthropoid ("protoanthropoid").

A lower jaw of Pondaungia cotteri from the Late Middle Eocene Pondaung Formation (Myanmar) confirms its anthropoid status.

Pondaungia cotteri is the largest primate known from the Late Middle Eocene Pondaung Formation, Myanmar. Its taxonomic status has been the subject of much debate because of the fragmentary nature of its remains. Initially described as an anthropoid, some authors recently have associated it with adapid primates. These debates have been fueled not only by the incompleteness of the fossils attributed to Pondaungia but also by the reticence of many authors to regard Asia as an important evolutionary theater for Eocene anthropoids. During the November 1998 Myanmar-French Pondaung Expedition, a right lower jaw was discovered that yields the most nearly complete dentition of Pondaungia cotteri ever found: it shows the complete horizontal ramus, alveoli for the second incisor and canine, three premolars, and three molars. The symphysis showed all characteristics of anthropoids but was unfused. The canine root is large, the first premolar is absent, and the second premolar is single-rooted, reduced, and oblique in the tooth row, as in anthropoids. The premolars show a reduced mesio-distal length compared with the tooth row, and their morphology is very similar to that of Amphipithecus mogaungensis. Therefore, the two Pondaung taxa appear to be closely related to each other, with Siamopithecus as their sister taxon.

A new primate from the Middle Eocene of Myanmar and the Asian early origin of anthropoids.

A new genus and species of anthropoid primate, Bahinia pondaungensis gen. et sp. nov., is described from the Yashe Kyitchaung locality in the Late Middle Eocene Pondaung Formation (Myanmar). It is related to Eosimias, but it is represented by more complete remains, including upper dentition with associated lower jaw fragment. It is interpreted as a new representative of the family Eosimiidae, which corresponds to the sister group of the Amphipithecidae and of all other anthropoids. Eosimiidae are now recorded from three distinct Middle Eocene localities in Asia, giving support to the hypothesis of an Asian origin of anthropoids.