CRANIAL RECONSTRUCTION OF A PREVIOUSLY UNDESCRIBED GLOBODONTAN ALLIGATORID FROM THE HELL CREEK FORMATION OF MONTANA

The Late Cretaceous sediments of Southeastern Montana have produced a number of fabulous crocodylian specimens. In the summer of 2008, the Burpee Museum of Natural History collected a well preserved specimen of a small-bodied, globodontan alligatorid from the Hell Creek formation [Late Maastrichtian] of Montana. This specimen is remarkably well-preserved, facilitating the recovery of a substantial portion of the cranial and post-cranial skeleton. Despite its exceptional quality, several important cranial elements are lacking, hindering attempts to elucidate its taxonomic identification and limiting its value as an educational tool. Under such circumstances, paleontologists and fossil preparators often incorporate the techniques of molding, casting and complimentary sculpture to aid the accurate reconstruction of extinct taxa known only from incomplete specimens. Here we restrict our discussion to details of the cranium; however, understanding the anatomy of the postcranial skeleton is also vital to identifying and describing this unique specimen. Accurate reconstruction of the cranium was aided by the preservation of several key elements (e.g., a nearly complete lower mandible, left maxilla and left pre-maxilla) that provided important information regarding its overall size and dimensions. Whenever a paired element was missing from one side of the body (e.g., the articular, maxilla, pre-maxilla and ectopterygoid) , sculpturing techniques were used to mirror the anatomy of the preserved side. Elements that were completely lacking were reconstructed using a combination of allometry and comparative study of other closely-related alligatorids. These techniques resulted in a uniquely shaped cranium measuring 175mm in length and 109mm across the squamosals. The overall size and distinct appearance of the cranium is unlike that of any other crocodylian previously described from the Hell Creek formation. Future analysis of the specimen’s post-cranial elements may further our understanding of this specimen.