Prenocephale (meaning “sloping forehead”) was a pachycephalosaurid dinosaur species from the Late Cretaceous of Mongolia. It was closely related to Homalocephale which may have been Prenocephale juveniles.

Ghedoghedo, CC BY-SA 3.0, via Wikimedia Commons

Adult Prenocephale weighed in at 130 kg (290 lb) and was approximately 2.4 metres (8 ft). Prenocephale’s head was rounder and more sloping than the flattened, wedge-shaped skull of Homalocephale. This could be a juvenile trait that may also be seen in the early stages of Pachycephalosaurus’ growth. There were small bumps and bony spikes in the dome. It was found in the Nemegt Formation, high upland forests. Not in the dry deserts of Mongolia.

Prenocephale, like other pachycephalosaurs is only known from skulls and a few small bones. Reconstructions of Prenocephale often show it as having the same basic body plan as all the Pachycephalosauria, a strong body with a thick neck and short forelimbs.

Prenocephale’s head was similar to Stegoceras’, but with closed supratemporal penestrae. Also, the paired grooves above the supraorbitals/prefrontals (along with a posterior parietal that restricts the frontal dome) are absent in Prenocephale. This distinguishes the species from Stegoceras as these features are more common in the former. Sullivan (2003) considered the North American Sphaerotholus to be a synonym for Prenocephale, but Longrich et. al. Schott, Evans (2016) and (2010) kept it as a separate genus using cladistic analysis. Homalocephale was considered a possible juvenile of Prenocephale because it did not have a dome and was discovered in the same chronological interval and location. However, new specimens of Prenocephale including one juvenile specimen suggest that Homalocephale is distinct, even though its holotype may be a juvenile.

Source: Wikipedia