Geology and Vertebrate Paleontology of a Lower Permian Deposit on the Brazos River, Baylor County Texas, with the Description of a New Genus and Species Of Acanthodian Fish

Abstract

A high concentration of vertebrate fossils is described from a Lower Permian Lueders Formation deposit. The study area is on the Salt Fork of the Brazos River, near the entrance to Miller's Creek, 22 km south of Seymour, Baylor County, Texas.  Remains of an undescribed genus and species of acanthodian fish make up more than 90 percent of the fossils; sharks, coelacanth and paleoniscoid fishes constitute the remainder, with the exception of a few fragments of amphibians and reptiles.  The dolostone matrix containing the fossils was deposited in shallow, near-shore marine water.  All of the vertebrates, except tetrapods, are considered to be marine. The acanthodian is typified by large size, fin spines being symmetrical in cross-section and without surface sculpture and scales consisting of a spongy bone core surrounded by concentric layers of orthodentine except externally, where it is covered with successive layers of an enameloid.  Each scale bears an elongated posterior spine.  Fauna from near Miller's Creek is less diverse in species content than the marine vertebrate fauna discovered in the Lueders Formation near Lake Kemp Dam, 30 km north-northeast of the Miller's Creek site, though both local faunas are nearly contemporary.  At Miller's Creek, acanthodians dominate the fauna;  at Lake Kemp Dam paleoniscoids constitute the bulk of the fauna.