Prenocephale Prenes
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''Prenocephale'' (meaning "sloping head") is a
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
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 pachycepha ...
dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
from the
Late Cretaceous The Late Cretaceous (100.5–66 Ma) is the more recent 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 ''cre ...
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 ...
of
Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...
. It was similar in many ways to its close relative, ''
Homalocephale ''Homalocephale'' (from 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, Mongolia, about ...
''.


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 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 ...
. 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 ''Pachycephalosaurus'' (; meaning "thick-headed lizard", from Greek ''pachys-/'' "thickness", ''kephalon/'' "head" and ''sauros/'' "lizard") is a genus of pachycephalosaurid ornithischian dinosaur. The type species, ''P. wyomingensis'', ...
''), 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 pachyceph ...
: 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 Pachycephalosauria, pachycephalosaurid (dome-headed) dinosaur that lived in what is now North America during the Late Cretaceous Period (geology), period, about 77.5 to 74 million years ago (mya). The first specim ...
'', albeit with closed supra
temporal fenestra Temporal fenestrae are openings in the temporal region of the skull of some amniotes, behind the orbit (eye socket). These openings have historically been used to track the evolution and affinities of reptiles. Temporal fenestrae are commonly (al ...
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
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 pachyceph ...
, a large
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
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") is a genus of pachycephalosaurid dinosaur, a group of dome-headed, herbivorous ornithischians, that lived during the Late Campanian stage (75-73 million years ago) of the Late Cretaceous in what is now M ...
'' the sister taxon to the ''Prenocephale''
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
, while sinking ''Sphaerotholus buchholtzae'' as a subjective
junior synonym In taxonomy, the scientific classification of living organisms, a synonym is an alternative scientific name for the accepted scientific name of a taxon. The botanical and zoological codes of nomenclature treat the concept of synonymy differently. ...
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 ancestra ...
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 ''Homalocephale'' (from 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, Mongolia, about ...
'' 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 A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...
modified from Evans ''et al.'', 2013.


Paleoenvironment

''Prenocephale'' lived in what is now 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 ...
, in high upland forests, not the dry deserts of
Mongolia Mongolia is a landlocked country in East Asia, bordered by Russia to the north and China to the south and southeast. It covers an area of , with a population of 3.5 million, making it the world's List of countries and dependencies by po ...
nowadays.


See also

* Timeline of pachycephalosaur research


References


External links

{{Taxonbar, from=Q134220 Pachycephalosauria Dinosaur genera Maastrichtian dinosaurs Nemegt Formation Taxa named by Teresa Maryańska Taxa named by Halszka Osmólska Fossil taxa described in 1974 Dinosaurs of Mongolia