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Prenocephale; Temporal range: Late Cretaceous, 70–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Holotype skull ZPAL MgD-I/104
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Dinosauria
Clade:	†Ornithischia
Clade:	†Neornithischia
Clade:	†Pachycephalosauria
Family:	†Pachycephalosauridae
Genus:	†Prenocephale; Maryańska & Osmólska, 1974
Species
	†P. prenes Maryńska & Osmólska, 1974 (type);
Synonyms
	Homalocephale? Maryanska & Osmólska, 1974;

Prenocephale (meaning "sloping head"^[1]) is a genus of small pachycephalosaurid dinosaur from the Late Cretaceous Nemegt Formation of Mongolia. It was similar in many ways to its close relative, Homalocephale.

Description

Adult Prenocephale measured 2.2 m (7.2 ft) in length and 40 kg (88 lb) in body mass.^[2] 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.^[3]

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.^[4] However, Longrich et al. (2010) and Schott and Evans (2016) kept Sphaerotholus as a distinct genus based on cladistic analysis.^[5]^[6]

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.^[7]

Below is a cladogram modified from Evans et al., 2013.^[8]

Pachycephalosauria

Wannanosaurus yansiensis

Pachycephalosauridae

	Colepiocephale lambei

	Hanssuesia sternbergi

	Stegoceras novomexicanum

	Stegoceras validum

Goyocephale lattimorei

Homalocephale calathocercos

Tylocephale gilmorei

Foraminacephale brevis

Amtocephale gobiensis

	Acrotholus audeti

	Prenocephale prenes

	Alaskacephale gangloffi

	Pachycephalosaurus wyomingensis

	Sphaerotholus buchholtzae

	Sphaerotholus goodwini

Paleobiology

As with most of its relatives, scientists do not yet know what these dinosaurs ate. However the premaxillary teeth and muzzle are not as wideset as in its relative Stegoceras, indicating different feeding preferences, possibly that Prenocephale was a more selective forager. Some scientists suggest that it may have been an omnivore, eating both plants and insects. However, most experts agree that Prenocephale (and the other pachycephalosaurs) browsed on leaves and fruit.

Paleoenvironment

It lived in what is now the Nemegt Formation, in high upland forests, not the dry deserts of Mongolia today.

References

T. Maryanska and H. Osmolska. 1974. Pachycephalosauria, a new suborder of ornithischian dinosaurs. Palaeontologia Polonica 30:45-102.

^ "Prenocephale | Natural History Museum".
^ Paul, Gregory S. (2016). The Princeton Field Guide to Dinosaurs. Princeton University Press. p. 269. ISBN 978-1-78684-190-2. OCLC 985402380.
^ Palmer, D., ed. (1999). The Marshall Illustrated Encyclopedia of Dinosaurs and Prehistoric Animals. London: Marshall Editions. p. 137. ISBN 1-84028-152-9.
^ Robert M. Sullivan (2003). "Revision of the dinosaur Stegoceras Lambe (Ornithischia, Pachycephalosauridae)". Journal of Vertebrate Paleontology. 23 (1): 181–207. doi:10.1671/0272-4634(2003)23[181:ROTDSL]2.0.CO;2. S2CID 85894105.
^ Longrich, N.R., Sankey, J. and Tanke, D., 2010. Texacephale langstoni, a new genus of pachycephalosaurid (Dinosauria: Ornithischia) from the upper Campanian Aguja Formation, southern Texas, USA. Cretaceous Research, . doi:10.1016/j.cretres.2009.12.002
^ Re: Sphaerotholus
^ David C. Evans, Shoji Hayashi, Kentaro Chiba, Mahito Watabe, Michael J. Ryan, Yuong-Nam Lee, Philip J. Currie, Khishigjav Tsogtbaatar, Rinchen Barsbold. (2017) Morphology and histology of new cranial specimens of Pachycephalosauridae (Dinosauria: Ornithischia) from the Nemegt Formation, Mongolia. Palaeogeography, Palaeoclimatology, Palaeoecology.
^ Evans, D. C.; Schott, R. K.; Larson, D. W.; Brown, C. M.; Ryan, M. J. (2013). "The oldest North American pachycephalosaurid and the hidden diversity of small-bodied ornithischian dinosaurs". Nature Communications. 4: 1828. Bibcode:2013NatCo...4.1828E. doi:10.1038/ncomms2749. PMID 23652016.