NEW MATERIAL OF SMALL DINOSAURS FROM THE UPPER CRETACEOUS ALLISON MEMBER, MENEFEE FORMATION, NEW MEXICO

An ongoing project conducted by the Western Science Center, Zuni Dinosaur Institute for Geosciences, and Southwest Paleontological Society has collected many fossils of large dinosaurs in the Upper Cretaceous (middle Campanian) Allison Member of the Menefee Formation in New Mexico. Small dinosaur material has been uncommon, but more has recently been discovered to flesh out this lesser known part of the vertebrate assemblage.

One such specimen is the nearly complete left maxilla of a juvenile hadrosaur. The maxilla is well-preserved with anatomical details such as the foramina on the lateral side and nine tooth positions with in situ teeth. From the morphology of the teeth and ectopterygoid shelf, the maxilla represents a derived hadrosauromorph. Currently, it is impossible to identify if it belongs to a saurolophine, lambeosaurine, or a basal hadrosaur like Eotrachodon. Ongoing fieldwork and more complete specimens, such as a recently collected adult partial skeleton, will allow further characterization of the Menefee’s hadrosaurs.

Another site yielded a fragmentary ornithomimid, including a manual claw, metatarsal fragment, and unidentifiable pieces, as well as gar scales. This is the first ornithomimid reported from the Menefee. The manual ungual is flattened ventrally and moderately curved. The flexor tubercle is reduced and placed distally.

A small partial tooth was collected from the same locality as the holotype of the tyrannosaurid Dynamoterror dynastes. Based upon its recurved and labiolingually compressed shape, and presence of rounded denticles on only the distal carina, this tooth is identified as Dromaeosauridae Morphotype A, previously described from Santonian–Campanian units in the San Juan Basin, including the Allison Member.