New Mexico Geological Society Annual Spring Meeting — Abstracts

Aetosaurs (Archosauria: Stagonolepididae) are a family of heavily armored reptiles that are a common component of Late Triassic faunas in Laurasia and portions of Gondwanaland (South America, India). The Bull Canyon Formation of east-central New Mexico yields five, or possibly six, taxa of aetosaurs. Typothorax coccinarum is represented by a complete, articulated skeleton (NMMNH P-12964), several portions of carapaces and numerous isolated scutes. Paratypothorax andressi is represented by one paramedian scute. Specimens of Desmatosuchus sp. consist of a few lateral scutes. Three new aetosaurs are easily distinguished from the other taxa by having body lengths much less than 2 m. The first new aetosaur is represented by a partially disarticulated skeleton. The paramedian scutes are unusually narrow and elongate with raised anterior bars. The second new aetosaur has proportionally short and wide paramedian scutes with a radial pattern and only occurs at one locality where it is represented by ?one partial individual. A sixth possible taxon is represented by small paramedian scutes with a pattern of simple pits, which lack a ventral bar. The lower Bull Canyon Formation contains all six taxa. The co-occurrence of Typothorax, Paratypothorax and Desmatosuchus indicates an early Norian age (early Typothorax biochron) and a correlation with the Post quarry of the Cooper Member of the Dockum Formation in Texas and the lower Painted Desert Member of the Petrified Forest Formation in Arizona. Only Typothorax occurs in the upper Bull Canyon Formation. This indicates a middle-late Norian age (late Typothorax biochron) and correlation with the Owl Rock Formation and upper Painted Desert Member in Arizona.