Faunal overview of the Mud Hill locality from the early Permian Vale Formation of Taylor County, Texas

摘要

The Texas red beds represent one of the richest series of early Permian deposits in the world. In particular, the Clear Fork Group has produced a diverse assemblage of temnospondyls, early reptiles, and synapsids. However, most of this material has been sourced from the oldest member, the Arroyo Formation, and the understanding of the paleoecosystem of the younger Vale and Choza formations is less well resolved. Here we present a previously undescribed Vale locality, the first vertebrate-bearing locality from the formation to be described in detail in several decades, from near Abilene, Texas with juvenile diplocaulids, captorhinids, abundant material of rare taxa such as Varanops and diadectids, and the first report of a recumbirostran ‘microsaur’ from the formation. This assemblage is atypical of early Permian deposits in the taxonomic and size distribution of the vertebrate fauna in comparison to other localities from the Vale Formation that preserve a greater abundance of aquatic taxa (e.g., fishes, Trimerorhachis) and synapsids (e.g., Dimetrodon). Minimal abrasion of the elements, relative articulation and association of the specimen of Varanops, and the paucity of aquatic taxa suggest an ephemeral pond deposit in which organisms were preserved essentially in situ. Our characterization of the locality also permits a revision and discussion of the vertebrate faunal assemblage of the Vale Formation.