D-23 Morphology of the frontal bones of Ampbipithecus discovered from the Pondaung Formation (latest middle Eocene, central Myanmar)

Two new frontal bone specimens (NMMP-KU 0229 & 0687) of Amphipithecus were discovered from the latest middle Eocene Pondaung Formation (central Myanmar). The former was collected together with a maxillary specimen identified as Amphipithecus based on the dental feature in 1999 field season, whereas the latter was discovered alone at another locality in 2000. In Amphipithecus the postorbital septum is not completed, but the postorbital constriction usually seen in most adapoids is not present. The interorbital part is so wide that the olfactory bulb should be very large. The metopic suture is unfused in NMMP-KU 0687 but fused in 0229, the associated maxilla of which preserves very worn upper dentition, suggesting this individual was rather old adult. In Amphipithecus the metopic suture would become fused during their growth.