A fossil primate of uncertain affinities from the earliest late eocene of Egypt

Paleontological work carried out over the last 3 decades has established that threemajor primate groupswere present in the Eocene of Africa - anthropoids, adapiforms, and advanced strepsirrhines. Here we describe isolated teeth of a previously undocumented primate from the earliest late Eocene (≈37 Ma) of northern Egypt, Nosmips aenigmaticus,whosephylogenetic placementwithin Primates is unclear. Nosmips is smaller than the sympatric adapiform Afradapis but is considerably larger than other primate taxa known from the same paleocommunity. The species bears an odd mosaic of dental features, combining enlarged, elongate, and molariform premolars with simple uppermolars that lack hypocones. Phylogenetic analysis across a series of different assumption sets variously places Nosmips as a stem anthropoid, a nonadapiform stem strepsirrhine, or even among adapiforms. This phylogenetic instability suggests to us that Nosmips likely represents a highly specializedmember of a previously undocumented,andpresumably quite ancient,endemicAfricanprimate lineage, the subordinal affinities of which have been obscured by its striking dental autapomorphies. Discriminant functions based onmeasurements of lower molar size and topography reliably classify extant prosimian primates into their correct dietary groups and identify Nosmips and Afradapis as omnivores and folivores, respectively. Although Nosmips currently defies classification, this strange and unexpected fossil primate nevertheless provides additional evidence for high primate diversity in northern Africa ≈37 million years ago and further underscores the fact that our understanding of early primate evolution on that continent remains highly incomplete.