[N] 2011 Stegoceras novomexicanum
Jasinski, S.E., and Sullivan, R.M. (2011). \\\\\\\"Re-evaluation of pachycephalosaurids from the Fruitland-Kirtland transition (Kirtlandian, late Campanian), San Juan Basin, New Mexico, with a description of a new species of Stegoceras and a reassessment of Texacephale langstoni\\\\\\\". Fossil Record 3. New Mexico Museum of Natural History and Science, Bulletin 53: 202–215.
Abstract—Two partial pachycephalosaurid skulls, from the upper Fruitland and lower Kirtland formations (Upper Cretaceous), are recognized as belonging to a new species Stegoceras Lambe, Stegoceras novomexicanum, n. sp. Stegoceras novomexicanum differs from the only other recognized species of Stegoceras (sensu Sullivan, 2003) in possessing: a reduced and sub-rectangular posteromedial extension of the parietal; parallel squamosal sutural surface contacts of the posteromedial extension of the arietal; enlarged and medially positioned supratemporal fenestrae; and a small (adult) size. Fusion of the frontal and parietal in one specimen, coupled with a smooth orsal surface of the frontoparietal dome, is consistent with an adult ontogenetic stage. Gross histology reveals four histomorphs, the fourth (outer-most layer) indicates rrested growth, further attesting to its mature state.
Stegoceras novomexicanum is known from, and restricted to, the upper Fruitland Formation (Fossil Forest Member) and lower Kirtland Formation (Hunter Wash Member); the collective vertebrates from these contiguous strata make up the Hunter Wash local fauna. Contrary to previous reports, the Prenocephale (= Sphaerotholus) -like pachycephalosaurids are not known from the early Kirtlandian, but are restricted to the Willow Wash local fauna of the upper Kirtland Formation (De-na-zin Member).
Stegoceras novomexicanum is temporally younger (Kirtlandian) than the well-known S. validum from the Judithian of Alberta, Canada. A reassessment of the newly named taxon Texacephale langstoni demonstrates that it is not based on diagnostic material and, therefore, is a nomen dubium.