New Mexico Geological Society Annual Spring Meeting — Abstracts

In recent years there has been considerable interest in the Early Permian tetrapod ichnofauna from the redbeds of central New Mexico. However, very little is known of the invertebrate ichnofauna in this area. Here, we add to this meager record the first documentation of Cruziana in the Abo Formation. These ichnofossils are from New Mexico Museum of Natural History locality 6708, in the upper part of the Abo Formation in the Cerros de Amado of Socorro County. The traces are preserved in convex hyporelief on mud-draped surfaces of several small slabs of ripple-laminated sandstone. The slab surfaces show numerous bilobate trails that consist of paired ridges and a median furrow. The ridges are covered with thin, uneven, closely-spaced transverse striations. All external trail widths are similar and typically approach 1 cm or less. The longest individual trail is 80 mm in length. Trail courses are straight to gently curved. Rheotaxic alignment of trails is seen. No associated or intergradational Rusophycus resting-type forms are present. These relatively small bilobate trails are assigned to Cruziana problematica (Schindewolf, 1921) based on the thin, closely-spaced transverse striations and the absence of markings external to the bilobate rows. C. problematica is ethologically considered a locomotion trace. Notostracan crustaceans are the probable producers of some C. problematica in North American Lower Permian nonmarine deposits. Further prospecting within the Cerros de Amado may prove valuable in increasing what is otherwise a poorly known record of Early Permian invertebrate ichnotaxa from central New Mexico.