The Face of Strigorhysis : Implications of Another Tarsier‐like, Large‐Eyed Eocene North American Tarsiiform Primate

The hypothesis that hypertrophic eyeballs were widespread among Eocene tarsiiform primates can be tested by qualitatively examining an integrated set of anatomical features involving the middle face, palate, and orbital floor that are also manifest in Tarsius . The North American anaptomorphine Strigorhysis , restudied via micro‐CT, is presented as an example, one of about nine fossil tarsiiforms (FTs) with moderately to enormously enlarged eyes—some possibly tarsier‐sized. The eyeballs of Strigorhysis likely were ectopic and comparable in relative size to the smallest‐bodied living tarsier, T. pumulis . These fossils, constituting approximately one‐third of the Eocene tarsiiform adaptive radiation and possibly others still known essentially from dental remains, appear to form a monophyletic group that includes Tarsius . Small‐eyed genera usually classified as omomyids, such as Teilhardina and Rooneyia , are not part of this clade. Although the precise affinities of Tarsius cannot yet be established, the widespread presence of meticulously similar orbital and facial morphology among the fossils suggest it is an ancestral condition—derived for haplorhines—shared by them and not multiply evolved via parallelism or convergence. Consequently, the rarer, tarsier‐like postcranial characters found only among European microchoerines, which all exhibit degrees of orbital hypertrophy, should be revisited as potential Tarsius synapomorphies. The overwhelming evidence from the skull and from phylogenetics makes it a vanishingly small possibility that Tarsius is more closely relate to anthropoids than to a subset of FTs. Anat Rec, 2011. © 2011 Wiley‐Liss, Inc.