Prenocephale (meaning "sloping head"
Discovery
The holotype specimen,
Z. Pal. No. MgD-I/104, consists of an isolated yet well-preserved skull, dorsal vertebrae and ribs, sacrum, femora, and caudal vertebrae. It was discovered by the Polish-Mongolian Paleontological Expedition and was found at the Nemegt locality, in a sandstone layer of the
Nemegt Formation.
Additional specimens have been recovered from the Bügiin Tsav, Guriliin Tsav, and Tsaagan Khushuu localities of the formation.
Description
Adult
Prenocephale measured in length and in body mass.
Unlike the flattened wedge-shaped skull of
Homalocephale (a possible juvenile trait also potentially seen in early growth stages of
Pachycephalosaurus), the head of
Prenocephale was rounded and sloping. The dome had a row of small bony spikes and bumps.
Like some other pachycephalosaurs, Prenocephale is known only from skulls and a few other small bones. For this reason, reconstructions usually depict Prenocephale as sharing the basic body plan common to all of the other Pachycephalosauria: a stout body with a short, thick neck, short forelimbs and tall hind legs.
The head of Prenocephale was comparable to that of Stegoceras, albeit with closed supratemporal fenestrae. Also, the paired grooves above the supraorbitals/prefrontals (along with a posterior parietal that restricts the frontal dome) are absent in Prenocephale. This differentiates the species from Stegoceras, as such features are common in the latter.
Classification
Prenocephale is a member of the Pachycephalosauria, a large
clade of herbivorous/omnivorous dinosaurs from the Late Cretaceous. Robert Sullivan considered
Foraminacephale,
"Prenocephale" edmontonensis, and
Sphaerotholus goodwini to form a clade with the Asian taxon
P. prenes. He considered
Tylocephale the sister taxon to the
Prenocephale clade, while sinking
Sphaerotholus buchholtzae as a subjective
junior synonym of
"P." edmontonensis. They all possess a distinct row of nodes on the
squamosal and parietal areas of the skull roof.
However, Longrich et al. (2010) and Schott and Evans (2016) kept
Sphaerotholus as a distinct genus based on cladistic analysis.
Homalocephale has been viewed as a possible juvenile of Prenocephale due to the lack of a dome and its discovery in the same location and chronological interval, but new specimens of Prenocephale, including a juvenile specimen, suggest that Homalocephale, even if its holotype is a juvenile, is distinct.
Below is a cladogram modified from Evans et al., 2013.
Paleoenvironment
Prenocephale lived in what is now the
Nemegt Formation, in high upland forests, not the dry deserts of
Mongolia nowadays.
See also
-
Timeline of pachycephalosaur research
External links
