Abstract

Palaeictops is a genus of Early Cenozoic Leptictidae, currently comprising six species known from Eocene faunas in the United States and Canada. Two new species, Palaeictops altimontis and P. robustus, are represented by nearly complete skulls and mandibles from the Tepee Trail (Middle Eocene) and Uinta (Middle Eocene) formations of Wyoming and Utah, respectively. They are similar to other species of Palaeictops in having a single sagittal crest, small suprameatal foramen, and an expanded cochlear fossula. Phylogenetic analysis recovered a monophyletic Palaeictops and a sister relationship of P. bicuspis and P. multicuspis with P. matthewi sister to this clade. The subfamily Leptictinae is herein recognized to comprise Blacktops, Leptictis, Megaleptictis, and Palaeictops. This group is distinctive in having a number of features that indicate a less sectorial cheektooth dentition than in the nonleptictine Prodiacodon and Myrmecoboides. The leptictines Palaeictops and Leptictis are also known from postcranial elements, and these show features, such as the distally fused tibia and fibula, that distinguish them from the condition in Prodiacodon. The Late Cretaceous genus Gypsonictops is used as an outgroup for the phylogenetic assessment of leptictids herein, but it remains uncertain whether this taxon has a close relationship with other leptictids or lies outside the crown group Placentalia.