''Prenocephale'' (meaning "sloping head") is a

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of small

pachycephalosaurid Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachycephal ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

from the

Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the ...

Nemegt Formation The Nemegt Formation (also known as Nemegtskaya Svita) is a geological formation in the Gobi Desert of Mongolia, dating to the Late Cretaceous. The formation consists of river channel sediments and contains fossils of fish, turtles, crocodilians, ...

Mongolia Mongolia; Mongolian script: , , ; lit. "Mongol Nation" or "State of Mongolia" () is a landlocked country in East Asia, bordered by Russia to the north and China to the south. It covers an area of , with a population of just 3.3 million, ...

. It was similar in many ways to its close relative, ''

Homalocephale ''Homalocephale'' (from Ancient Greek, Greek ὁμαλός, ''homalos'', "even", and κεφαλή, ''kephalē'', "head") is a genus of pachycephalosaurid dinosaur that lived during the Late Cretaceous period of what is now the Nemegt Formation, M ...

''.

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 Pachycephalosauria (; from Greek παχυκεφαλόσαυρος for 'thick headed lizards') is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachycepha ...

: a stout body with a short, thick neck, short forelimbs and tall hind legs. The head of ''Prenocephale'' was comparable to that of ''

Stegoceras ''Stegoceras'' is a genus of pachycephalosaurid (dome-headed) dinosaur that lived in what is now North America during the Late Cretaceous period, about 77.5 to 74 million years ago (mya). The first specimens from Alberta, Canada, were descri ...

'', albeit with closed supra

temporal fenestra An infratemporal fenestra, also called the lateral temporal fenestra or simply temporal fenestra, is an opening in the skull behind the orbit in some animals. It is ventrally bordered by a zygomatic arch. An opening in front of the eye sockets ...

e. 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

, a large

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

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 ''Tylocephale'' (meaning "swollen head", from the Greek ''τυλη'' meaning 'callus' or 'hard swelling' and ''κεφαλη'' meaning 'head') is a genus of pachycephalosaurid dinosaur from the Late Cretaceous period. It was a herbivorous dinos ...

'' the sister taxon to the ''Prenocephale''

, while sinking ''Sphaerotholus buchholtzae'' as a subjective

junior synonym The Botanical and Zoological Codes of nomenclature treat the concept of synonymy differently. * In botanical nomenclature, a synonym is a scientific name that applies to a taxon that (now) goes by a different scientific name. For example, Linna ...

of ''"P." edmontonensis''. They all possess a distinct row of nodes on the

squamosal The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

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.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'', . ''

'' 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.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. Below is a

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

modified from Evans ''et al.'', 2013.

Paleobiology

As with most of its relatives, scientists do not yet know what these dinosaurs ate. However the

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

ry teeth and muzzle are not as wideset as in its relative ''

'', indicating different feeding preferences, possibly that ''Prenocephale'' was a more selective forager. Some scientists suggest that it may have been an

omnivore An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nutr ...

, 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

, in high upland forests, not the dry deserts of

today.

References

* T. Maryanska and H. Osmolska. 1974. Pachycephalosauria, a new suborder of ornithischian dinosaurs. ''Palaeontologia Polonica'' 30:45-102.

External links