Evolutionary ecology of fossil primates in southeast Asia. Results of two pilot studies
Résumé
Cenozoic Southeast Asia was a key area for primate evolution. Important episodes of diversification and evolution of anthropoids and hominoids took place there. Our project focuses on the evolutionary ecology of these fossil primates and the associated fauna. We performed isotopic paleoecological tracking on the fossil tooth material recovered from 1998 to 2020 by the Myanmar-French paleontological team from the middle Eocene Pondaung Formation (40 Ma) and the late Miocene Irrawaddy Formation (10–9 Ma), both located in the Central Basin of Myanmar. Our goal is to shed light on the ecological structure of the mammalian communities around the Eocene anthropoid and Miocene hominoid primates.
Carbon and oxygen isotopic analyses on the tooth enamel carbonates of the ungulates from the Pondaung Formation were collected in a pilot study. δ13C values point towards an open forest habitat. Also, serial sampling on some of the teeth revealed a sinusoidal pattern of δ18O values, confirming seasonality and monsoon-like events during the middle Eocene. Oxygen isotopic results suggest semi-aquatic habitats for the Amynodontidae, but not for the anthracotheres, in contrast with more recent members of this group.
All analyzed taxa from the Miocene Irrawaddy Formation lived in a pure C3 open forested environment with no evidence of C4 vegetation. Carbon and oxygen isotopic data of Khoratpithecus (MFI-K171) tooth enamel are consistent with a canopy habitat and a diet essentially frugivorous, in agreement with tooth wear analysis from Thailand.
The combination of isotopic analyses with dental microwear texture analysis will allow us to further understand niche partitioning and dynamics of these ecosystems.