New Mexico Geological Society Annual Spring Meeting — Abstracts

New Mexico Museum of Natural History (NMMNHH) locality 846 is an Early Permian tracksite in the Abo Tongue of the Hueco Formation in the Robledo Mountains of south-central New Mexico. This locality preserves one of the most diverse Permian ichnofaunas known. One important fatet of the large collection from this site is that several trackway specimens preserve interactions between animals. One such specimen is NMMNH P-14653 which , preserves two vertebrate trackways that converge perpendicularly. The trackways are preserved on the mud cracked surface of a silty sandstone with a mudstone drape. The sandstone is a micaceous litharenite which is pale red (5R 6/2) in color. The larger trackway (pes impression length 15 cm) is about 1.8 m-long and can be assigned to the ichnogenus Dimetropus. This trackway continues across the entire specimen. A second trackway of an unidentified ichnotaxon intersects the Dimetropus trackway. The smaller trackway has pentadactyl pedal impressions which are 1 cm long and a trackway width of 2 cm. The narrow, elongate impressions of the digits show increasing length from I-V and there is a deep, crescentic heel impression.

The trackway of the unidentified animal terminates as it intersects that of Dimetropus. Careful examination of the surface on the other side of the Dimetropus trackway does not indicate either further tracks of the smaller animal or any change in lithology. Therefore, we tentatively suggest that the Dimetropys trackmaker lifted the smaller animal off the substrate. Dimetropus represents a carnivorous sphenacodont and the most parsimonious explanation of this behavior is that the larger animal consumed the smaller.

Similar animal interactions that indicate predation have been reportedfrom the Permian, based on trackway evidence, from the Cedar Mesa Formation of Utah (vertebrate vs. vertebrate) and the Coconino Formation of Arizona (vertebrate vs. invertebrate). Other examples are also present in the collection from NMMNH locality 846. Direct trackway evidence of predation currently appears to be limited to the Paleozoic.