Reptile Assemblage from the Middle Triassic Moenkopi Formation of New Mexico

A very well-written and detailed paper demonstrating the importance of apomophy based identifications when assigning scrappy material to taxa for accurate determination of faunal assemblages. Further demonstrates the abundance of archosaurs, including primitive poposauroids and a possible shuvosaurid, in the Early to Middle Triassic rocks of the American Southwest.

Schoch, R. R., Nesbitt, S. J., Mueller, J. M., Lucas, S. G., and J. A. Boy, J. A. 2009, The reptile assemblage from the Moenkopi Formation (Middle Triassic) of New Mexico. Neues Jahrbuch für Geologie und Paläontologie Abhandlungen, DOI: 10.1127/0077-7749/2009/0030; Stuttgart.

Abstract: Focused collecting and excavation in the Moenkopi Formation (Anton Chico Member)of north-central New Mexico yielded a large quantity of tetrapod bones. Most of the finds were collected from intraformational conglomerates, and consist of isolated bones or bone fragments. The most abundant large members of the assemblage, the archosaurs, include at least three taxa: (1) a primitive suchian or archosauriform, (2) a primitive poposauroid (Arizonasaurus babbitti), and (3) a taxon similar to shuvosaurids. Less abundant remains are tentatively referred to archosauromorphs with rhynchosaur affinities. An analysis of the tetrapod Lagerstätten reveals that primary deposits formed in lakes that were located on floodplains. In these lakes, autochthonous conchostracans, actinopterygians, coelacanths, and temnospondyls were evidently preserved. Fluvial reworking of lacustrine deposits resulted in a secondary deposition of bones, teeth, coprolites, and wood in channel-borne conglomerates. However, the large amount of elements from terrestrial tetrapods indicates that these conglomerates acquired bones from additional primary deposits (?channels, paleosols?) that are still unknown.

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