New Mexico Geological Society Annual Spring Meeting — Abstracts

The extensive vertebrate ichnofauna at Clayton Lake State Park, northeastern New Mexico, has been the subjective of several publications. Tracks here occur in the upper Mesa Rica Sandstone and lower Pajarito Formation (Lower Cretaceous: late Albian) in the dam spillway. Early studies suggested the presence of a diverse ichnofauna including half a dozen ichnotaxa representing ornithischians, theropods (including web-footed theropods) and pterosaurs. Recent work indicates that only three vertebrate ichnotaxa are present: (1) more than 90% of the tracks are tridactyl ornithischian tracks assigned to Caririchnium sp. (including putative web-footed theropod tracks); (2) tridactyl theropod tracks; and (3) crocodilian swimming traces (putative pterosaurian tracks).

The Clayton Lake tracksite (CLT) is one of the largest individual sites in the Dakota megatracksite (DM) (popularly called the "Dinosaur Freeway"). CLT is similar to other DM tracksites in having a preponderance of iguanodontid tracks and relatively few theropod tracks. It differs from several other DM tracksites by including crocodilian tracks and in having tracks on multiple bedding planes. It differs from all DM sites in exhibiting a large range of track preservation as a result of variability in substrate saturation. A new map of the site is being prepared and this will provide inferences on individual and group behavior.