New Mexico Geological Society Annual Spring Meeting — Abstracts

Parasaurolophus is one ofthe more rare and unusual of the crested duck-billed dinosaur. A new skull of Parasaurolophus (long-crested form), from the Upper Cretaceous De-na-zin Member, Kirtland Fonnation, represents the most complete skull ofthis genus to be collected from New Mexico. It also has the most complete narial crest ofany specimen collected to date. The specimen (New Mexlco Museum ofNatural History P-25100) is well-preserved and consists ofthe skull roof and braincase, a nearly complete narial crest, the left cheek region and left mandible.

The crest ofthe new skull differs from those of other described specimens of Parasaurolophus. The external crest morphology is unusual in that the dorsal surface is marked by numerous "vascular grooves." Computerized tomography (CT scans), the first reported for Parasaurolophus, reveal that the internal morphology ofthe crest in the new specimen is much more complex than has been previously documented for this dinosaur. Previous workers described a maximum of only three pairs of internal chambers within the crest based on broken sections ofthe crests in other specimens. Our CT scans reveal nine to eleven distinct chambers within certain areas ofthe crest in NMMNH P-25100. The discrepancies between morphology ofthe crest of the new Parasaurolophus skull, and previously described specimens, remain unexplained at this time. Forthcoming detailed analysis ofthe CT scan data will reveal the distribution and shape ofthese chambers.