The 81st Annual Meeting of the American Association of Physical Anthropologists (2012)


Petrosal anatomy of Afradapis longicristatus (Primates, Adapiformes)

E. CHRISTOPHER KIRK1, ERIK R. SEIFFERT2 and ELWYN L. SIMONS3.

1Anthropology, University of Texas at Austin, 2Anatomical Sciences, Stony Brook University, 3Evolutionary Anthropology, Duke University

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Afradapis is a large (2-3 kg) adapiform primate known from the early late Eocene BQ-2 locality in the Fayum Depression, Egypt. Here we report the discovery of two isolated petrosals from BQ-2 that are referable to Afradapis based on size and morphology. Both petrosals preserve portions of the canals for the facial nerve and branches of the internal carotid artery. As in other adapiforms, the internal carotid enters the middle ear posterolaterally near the stylomastoid foramen, and the stapedial and promontory canals divide on the promontorium infero-medial to the fenestra cochleae. The stapedial and promontory canals are nearly equal in diameter and follow the “transpromontorial” route that is probably plesiomorphic for crown primates. In these features, Afradapis is similar to many adapiforms and omomyiforms but differs from crown haplorhines. The preserved portions of the facial canal are unremarkable except in one respect: the hiatus Fallopii (intracranial exit for greater petrosal nerve) is very large, exceeding the diameter of the facial canal by 30-50%. It is likely that the geniculate ganglion was lodged in this large opening, as occurs in 5% of humans. This peculiar morphology is apparently typical for Afradapis because it is preserved in both known specimens, but is not seen in other adapiforms. Both specimens also demonstrate that the mastoid was heavily pneumatized, as in adapines and Mahgarita. The petrosal anatomy of Afradapis is consistent with its previous placement as a derived adapiform stem strepsirrhine, and provides no evidence for a phylogenetic link with anthropoids.

This research has been funded by the Research Foundation of SUNY, and grants from the US National Science Foundation and The Leakey Foundation to E.R.S. and E.L.S.

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