The upper dentition and face of Pondaungia cotteri from central Myanmar

A specimen of Pondaungia from the late middle Eocene Pondaung Formation in central Myanmar includes maxillary fragments and parts of the dentition, some hitherto undocumented, including the upper central incisor, canine, premolars and molars. Pondaungia has a large spatulate I1 closely resembling that of crown anthropoids. It possesses a stout projecting upper canine (like anthropoids) but differs from that tooth of crown anthropoids in lacking a strong mesial groove. There are three upper premolars of which P2 is distinctly smaller than P3 or P4. P3 has a buccolingually oriented mesial profile and an inflated distal profile resembling that of parapithecids and crown anthropoids. The distolingual molar cusp is a hypocone and is not homologus with the "pseudohypocone" of notharctines because the cusp is neither twinned with the protocone nor attached to a Nannopithex-fold. Pondaungia has a stout zygomatic root with a strongly demarcated muscle scar for the superficial masseter situated well above the occlusal plane. The inferior orbital margin is not preserved but the inflated suborbital region allows for the inference that the orbit was small. This specimen is not sufficiently well preserved to identify if there was postorbital closure. However, a specimen of the frontal bone of Amphipithecus shows that its orbital septum was absent or poorly developed. If, as commonly supposed, Pondaungia andAmphipithecus are sister taxa, postorbital closure was probably absent in Pondaungia. The large incisors, molars with poorly developed crests and thick enamel, together with the stoutly developed and strong dorsal component of the force vector of the superficial masseter muscle suggest that Pondaungia had a diet low in fiber, but that included hard food objects like nuts or seeds. The present material adds to the structural similarities between Pondaungia and anthropoids, but whether these similarities are due to shared descent or functional and adaptive convergence remains unresolved.