A new vertebrate fauna from the Lower Cretaceous Holly Creek Formation of the Trinity Group, southwest Arkansas, USA

Celina A Suarez; Joseph Frederickson; Richard L Cifelli; Jeffrey G Pittman; Randall L Nydam; ReBecca K Hunt-Foster; Kirsty Morgan

doi:10.7717/peerj.12242

A new vertebrate fauna from the Lower Cretaceous Holly Creek Formation of the Trinity Group, southwest Arkansas, USA

PeerJ. 2021 Oct 21:9:e12242. doi: 10.7717/peerj.12242. eCollection 2021.

Authors

Celina A Suarez¹, Joseph Frederickson², Richard L Cifelli³, Jeffrey G Pittman⁴, Randall L Nydam⁵, ReBecca K Hunt-Foster⁶, Kirsty Morgan¹

Affiliations

¹ Department of Geosciences, University of Arkansas at Fayetteville, Fayetteville, Arkansas, USA.
² Weis Earth Science Museum, University of Wisconsin Oshkosh Fox Cities Campus, Menasha, WI, USA.
³ Department of Vertebrate Paleontology, Sam Noble Oklahoma Museum of Natural History, University of Oklahoma, Norman, OK, USA.
⁴ Ouachita Mountains Biological Station, Mena, Arkansas, USA.
⁵ Arizona College of Osteopathic Medicine, Midwestern University, Glendale, Arizona, USA.
⁶ Dinosaur National Monument, Jensen, UT, USA.

Abstract

We present a previously discovered but undescribed late Early Cretaceous vertebrate fauna from the Holly Creek Formation of the Trinity Group in Arkansas. The site from the ancient Gulf Coast is dominated by semi-aquatic forms and preserves a diverse aquatic, semi-aquatic, and terrestrial fauna. Fishes include fresh- to brackish-water chondrichthyans and a variety of actinopterygians, including semionotids, an amiid, and a new pycnodontiform, Anomoeodus caddoi sp. nov. Semi-aquatic taxa include lissamphibians, the solemydid turtle Naomichelys, a trionychid turtle, and coelognathosuchian crocodyliforms. Among terrestrial forms are several members of Dinosauria and one or more squamates, one of which, Sciroseps pawhuskai gen. et sp. nov., is described herein. Among Dinosauria, both large and small theropods (Acrocanthosaurus, Deinonychus, and Richardoestesia) and titanosauriform sauropods are represented; herein we also report the first occurrence of a nodosaurid ankylosaur from the Trinity Group. The fauna of the Holly Creek Formation is similar to other, widely scattered late Early Cretaceous assemblages across North America and suggests the presence of a low-diversity, broadly distributed continental ecosystem of the Early Cretaceous following the Late Jurassic faunal turnover. This low-diversity ecosystem contrasts sharply with the highly diverse ecosystem which emerged by the Cenomanian. The contrast underpins the importance of vicariance as an evolutionary driver brought on by Sevier tectonics and climatic changes, such as rising sea level and formation of the Western Interior Seaway, impacting the early Late Cretaceous ecosystem.

Keywords: Chondrichthyes; Crocodile; Dinsaur; Early Cretaceous; Holly Creek Formation; Lissamphibian; Paleobiogeography; Pycnodont fish; Trinity Group; Turtles.

Grants and funding

This work is supported by the National Science Foundation FRES 1925896 and DEB-9870173. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.