A new species of trionychid turtle from the Upper Cretaceous (Campanian) Fruitland Formation of New Mexico, USA

Abstract

AbstractNew shell material of a trionychid turtle from the Upper Cretaceous (upper Campanian) Fossil Forest Member of the Fruitland Formation of northwestern New Mexico represents a new species,Gilmoremys gettyspherensis. The material consists of right costals I–III, V, VI, and VIII, left costals V, VII, and VIII, the left half of the entoplastron, the right hypo- and xiphiplastron, and the left hyo-, hypo-, and xiphiplastron. The specimen shows great similarities to the Late Cretaceous (Maastrichtian) trionychidGilmoremys lancensis(Gilmore, 1916) by having a relatively thin shell, carapacial sculpturing consisting of fine pits combined with extended sinusoidal ridges or grooves, free costal rib ends, presence of a preneural, a distally constricted costal I and distally expanded costal II, two lateral hyoplastral processes, low hyoplastral shoulders, and full midline contact of the elongate xiphiplastra, but differs by being smaller, having raised sinusoidal ridges on the carapace instead of grooves, less distally expanded costals II, and less elongate xiphiplastra. Phylogenetic analysis placesGilmoremys gettyspherensisn. sp. as sister toGilmoremys lancensisnear the base of the clade Plastomenidae. Like the majority of previously described plastomenid materials, the type specimen ofGilmoremys gettyspherensisn. sp. was collected from a mudstone horizon, suggesting a preference for ponded environments.UUID:http://zoobank.org/e7165061-d86b-46b7-a1f8-c31f5a8ed628