Paleoecology of Khoratpithecus ayeyarwadyensis. Ecological niche modelling using stable isotopes
Résumé
Southeast Asia was a key area for hominoid diversification in the Miocene. Many different species are known from a large area spanning from India to southern China. The focus of this study is Khoratpithecus ayeyarwadyensis from the Irrawaddy Fm. (~9 Ma) in Myanmar. We used carbon and oxygen stable isotope analysis of the carbonate fraction of the enamel of this hominoid as well as its associated mammalian fauna to reconstruct its paleoecology and to conduct modelling of the isotopic niches of these fossil animals. With our data we explored if Khoratpithecus was frugivorous, where in the forest canopy it foraged, and we characterized the vegetation type and its density in the habitat of this fossil pongine. The isotopic niches were modelled using Bayesian statistics with the R package SIBER. In contrast with previous studies, we propose an ecological rather than a dietary or trophic niche, given the specific isotopes we analyzed. K. ayeyarwadyensis was then compared to other members of the pongine clade such as contemporaneous Sivapithecus and Indopithecus from Pakistan and India, respectively, as well as Pleistocene Gigantopithecus, and Pleistocene and extant Pongo. With this approach, we wanted to explore if there is evidence for ecological continuity in the pongine clade or if the variety of subsistence strategy was, like species diversity, greater in the past than it is now. An improved understanding of Khoratpithecus and comparing it to other contemporaneous fossil hominoids is crucial to understand the evolutionary ecology history of the extant orangutans (Pongo).