The diversity of cimolestan mammals within the White River Group of South Dakota and Nebraska

Clint Boyd

doi:10.4202/app.2011.0204

Abstract

A new Late Carboniferous cnemidolestodean insect Xixia huban gen. et sp. nov., is described from the Xiaheyan locality (Zhongwei City, Ningxia, China; Tupo Formation). Its combination of character states and observed variants on the wing venations are indicative of homologies shared with more derived members of the order. In particular it is ascertained that MP runs fused with CuA and CuA + CuPa, but is not usually visible as a distinct vein. The new genus exhibits previously unknown coloration pattern composed of dark patches distributed over the whole forewing (as opposed to regular stripes or rows of spots, previously documented in the group). The comparatively abundant sample makes it one of the best documented cnemidolestodeans to date.

Highlights

We show that the synonymization is unjustified, owing to distinct differences between these taxa in the mandibular tooth count (1-1-3-3 vs. ?-1-4-3), the identity of the enlarged anterior mandibular tooth, and the morphology of the crown of m3
We refer a specimen recently collected from the Early Oligocene Brule Formation within the Badlands National Park (BADL 16917) to Chadronia sp., making it the youngest occurrence of a pantolestan from North America
Examination of an additional specimen (FMNH UC 349) revealed the presence of a further cimolestan taxon in the White River Group of South Dakota, the poor quality of the locality and stratigraphic data associated with this specimen precludes erecting a formal name

Summary

Introduction

The synonymization of the cimolestan taxa Cymaprimadon and Chadronia from the Late Eocene Chadron Formation is consistently upheld, despite a lack of supporting evidence. We show that the synonymization is unjustified, owing to distinct differences between these taxa in the mandibular tooth count (1-1-3-3 vs ?-1-4-3), the identity of the enlarged anterior mandibular tooth (incisor versus canine), and the morphology of the crown of m3 (e.g., paraconid on m3 in Cymaprimadon).

Results

Conclusion