On Bahinia pondaungensis, an Alleged Early Anthropoid

Abstract

In order to assess the orientation of the orbit of Bahinia, a middle Eocene fossil from Mynamar that has been inter-preted as an anthropoid, laser surface scanning was used to develop three-dimensional models of the one facial specimen of Bahinia for comparison with Notharctus and Rooneyia, examples of a relatively early strepsirhine and haplorhine, respectively. Paired 3D montages were produced by graphically resizing Bahinia to the same molar lengths as the reference fossils and aligning them according to the contour and position of the inferior orbital mar-gin. The composites indicate that while the orbit of Bahinia appears to be relatively small, as previously reported, its placement more closely resembles the laterally facing orbit of Notharctus than the anteriorly facing orbit of Rooneyia, which resembles anthropoids. In the size and shape of the snout, depth of the maxilla, and orientation of the toothrow in the face, Bahinia shares a distinctive resemblance with Notharctus, not with Rooneyia. Since the dental and gnathic features presented as evidence that Bahinia is an anthropoid also are often found among adapi-forms, in which case they are generally understood to be convergent similarities to some anthropoid characters, we conclude that a more cogent argument can be made that Bahinia is a strepsirhine, with a large face and small, laterally facing orbits. Bahinia thus contributes little to the argument that the Chinese eosimiids are anthropoids.