Revision of the hadrosaurid Prosaurolophus: Diversity and Stasis
Last week saw the publication of a major revsion of the flat-headed hadrosaurid Prosaurolophus. The paper was lead by Chris McGarrity, and represents the lion-share of his MSc work that he completed in the lab about a year and a half ago. Nic Campione also contributed his hadrosaur expertise to the project. The study focuses on describing and quantifying the cranial variation in the type species, Prosaurolophus maximus, based on numerous complete, articulated skulls from the type locality of Dinosaur Provincial Park (Campanian, Alberta, Canada). The known skulls range in size from 685 mm to just over a meter in total length, and permit study of a hypothesized ontogenetic series for this taxon. Understanding patterns of growth and variation in the sample from Dinosaur Park is used to evaluate the validity of the second species in the genus, P. blackfeetensis. This taxon was named on the basis of geologically younger material from Montana (Two Medicine Formation: Campanian) and was diagnosed by putative morphological differences in the nasal crest. However, considerable nasal crest variation in the sample from the Dinosaur Park Formation does not permit quantitative differentiation of P. blackfeetensis from P. maximus. Furthermore, a species-level phylogenetic analysis of saurolophines that includes both P. maximus and P. blackfeetensis as originally defined recovers them as sister taxa that do not differ morphologically in the character matrix. Based on both the morphometric and phylogenetic data, this study supports the hypothesis that P. blackfeetensis is a junior synonym of P. maximus, thereby substantially increasing its temporal range to 1.6 million years, and suggesting a concomitant period of morphological stasis in this taxon.
The paper is quite detailed, and figures virtually all of the articulated skulls of P. maximus from Dinosaur Provincial Park (n=11). Congrats to Chris for now having his entire MSc published.
McGarrity, C. T., N. E. Campione, and D. C. Evans. 2013. Cranial anatomy and variation in Prosaurolophus maximus (Dinosauria: Hadrosauridae). Zoological Journal of the Linnean Society 167(4): 531-568. Available here.