[N] 2006 New species of Gryposaurus from the Kaiparowits fm. of Utah
Gates, T. & Sapmson, S. (2006) A new species of Gryposaurus (Dinosauria: Hadrosauridae) from the Upper Campanian Kaiparowits formation of Utah. JVP 26(3) Abstracts pp.65
Gryposaurus is a non-crested (hadrosaurine) hadrosaur characterized by a deep and massive skull possessing an arched nasal “hump” anterior to the orbits. Three species are currently recognized, G. notabilis, G. incurvimanus, and G. latidens, based on the relative position of the nasal hump, shape of the posterior nares, and relative size of the dentition. Recent work in the Kaiparowits Formation, exposed within Grand Staircase-Escalante National Monument, south-central Utah, has yielded a fourth Gryposaurus species, making this genus the most diverse within Hadrosauridae. The new species, represented by multiple skull and postcranial specimens, is differentiated from its congeners by the following characters: relatively deep, hyperrobust skull; anteroposteriorly narrow infratemporal fenestra; subcircular supratemporal fenestrae; and elongate, narrow paraoccipital process. The overall shape of the skull, as well as the morphology of the nasal, most closely resembles that of G. notabilis.
Collected skeletal remains demonstrate this new species is by far the largest known member of Gryposaurus. The latter finding is in keeping with taxonomic variation in body size among other late Campanian hadrosaurines from the Western Interior Basin, which tend to be significantly larger in the southern portion of the basin than in the north. The discovery of Gryposaurus in southern Utah expands the known geographic range of this taxon roughly 2000 km relative to contemporaneous occurrences of G. notabilis and G. incurvimanus in Alberta, making this genus one of the most widespread Campanian hadrosaurs. Nevertheless, the presence of a distinct taxon at the species level is consistent with the pattern observed for other late Campanian dinosaur clades found in both northern and southern portions of the Western Interior Basin, supporting the provincialism hypothesis.