New Mexico Geological Society Annual Spring Meeting — Abstracts

Amphisbaenia is a group of worm-like lizards that includes both extant and extinct species. The family Rhineuridae is the only known amphisbaenian family restricted to North America. The taxon Plesiorhineura tsentasi is the oldest (Paleocene, Torrejonian) known rhineurid in the fossil record and, recent phylogenetic studies show that rhineurids are the basal group of the Amphisbaenia. The holotype of Plesiorhineura tsentasi (NMMNH [New Mexico Museum of Natural History] P-12347, formerly UNM [University of New Mexico] NP-595) is known by the medial portion of the right jaw. The holotype was collected from the Nacimiento Formation at locality NMMNH L-312 (BUNM 77-184) in Torreon Wash, New Mexico. A recently collected specimen (NMMNH P-59245), which also represents the medial portion of the right jaw, came from the same locality and is considered to be a topotype of this taxon. The topotype has three teeth, of which the posterior-most is complete. It is missing the coronoid, splenial, and the anterior extension of the surangular, and thus is comprised solely of the dentary. The topotype conforms in every way to the holotype and is clearly referable to P. tsentasi based on its near identical morphology. Both specimens represent the same portion of the right dentary, suggesting this section is the most durable part of the lower jaw.