A faunivorous early sphenacodontian synapsid with a diastema

Abstract

Our knowledge on early sphenacodontian and edaphosaurid synapsids, the group that includes the origin of the mammalian lineage, largely arose from the Pennsylvanian Garnett locality in Kansas. A preliminary revision of the former "Haptodus" garnettensis found a greater diversity in the assigned material. The most striking deviation from the documented osteology is seen in a specimen comprising a lacrimal and associated maxilla. The diagnosis of this new form, Kenomagnathus scottae gen. et sp. nov., comprises a tall and shortened facial region, only two precanine teeth, and a distinct diastema. This is the oldest known diastema in synapsid evolution, and the first reported from a faunivorous member that lacks a precanine step, aside from Tetraceratops. This unique precanine morphology occurred independently from similar structures in Sphenacodontoidea. As for the edaphosaurid Gordodon, a specialized function in food processing is assumed for the diastema.

A Carboniferous synapsid with caniniform teeth and a reappraisal of mandibular size-shape heterodonty in the origin of mammals

“…1–10 kg), including the Carboniferous Haptodus and Ianthodon , and the Permian Palaeohatteria and Pantelosaurus [ 3 , 23 – 28 ]. Spindler [ 29 ] added to these the Kasimovian-aged Kenomagnathus scottae , a possible congener of Haptodus garnettensis which is from the same locality in eastern Kansas. Cutleria wilmarthi from the undivided Cutler of western Colorado [ 30 ] was previously suggested to be a basal sphenacodontian akin to these forms [ 3 , 24 , 31 ] but has since been shown to be the basalmost sphenacodontid [ 28 , 32 ].…”