New Mexico Geological Society Annual Spring Meeting — Abstracts

Pseudopalatus is a common genus of the Late Triassic phytosaur that has biochronologic significance; it is an index taxon of the Norian Revueltian lvf. A skull from the upper Carnian of central New Mexico thus is the first occurrence of this genus before the Norian. NMMNH (New Mexico Museum of Natural History) P-25745 is from NMMNH locality 3108, which is the type locality of Typothoraxantiquum. This locality is in the Tres Lagunas Member of the Santa Rosa Formation in Santa Fe County. NMMNH P-25745 is a partial skull represented by the region posterior to the mid point of the orbits. The anterior margin slopes anteriorly, so that the lateral temporal fenestrae are preserved on both sides. The skill is slightly flattened dorsoventrally. NMMNH P-25745 can be assigned to Pseudopalatus because it has a moderately wide postorbital-squamosal bar, supratemporal fenestrae that are short and narrow in dorsal view with narrow anterior margins and a parietal-supraoccipital complex that has an inverted U-shape.

This first occurrence of Pseudopalatus prior to the beginning of the Norian thus extends the temporal range of the genus. It suggests a need to refine the robust biochronology of the Late Triassic based on land-vertebrate biochrons.