''Homalocephale'' (from

Greek Greek may refer to: Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group *Greek language, a branch of the Indo-European language family **Proto-Greek language, the assumed last common ancestor of all kno ...

ὁμαλός, ''homalos'', "even", and κεφαλή, ''kephalē'', "head") is a genus of

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 ...

that lived during 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 ...

period of 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 ...

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 ...

, about 70 million years ago. The genus was described in 1974 by

Halszka Osmólska Halszka Osmólska (September 15, 1930 – March 31, 2008) was a Polish paleontologist who had specialized in Mongolian dinosaurs. Early life, family and education Osmólska was born in 1930 in Poznań. In 1949, she began to study biology at Fa ...

and

Teresa Maryańska Teresa Maryańska (1937 – 3 October 2019) was a Polish paleontologist who specialized in Mongolian dinosaurs, particularly pachycephalosaurians and ankylosaurians. She is considered not only as one of Poland's but also one of the world's leadin ...

, and consists of a single species, ''H. calathocercos''. Though ''Homalocephale'' has been regarded as a synonym (and juvenile form) of ''

Prenocephale ''Prenocephale'' (meaning "sloping head") 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''. Discovery The holotype specime ...

'', juvenile specimens of the latter indicate that they were distinct. ''Homalocephale'' was long and possibly an omnivore.

Discovery

The

type species In International_Code_of_Zoological_Nomenclature, zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the spe ...

, ''H. calathocercos'', was described from an incomplete skull and postcranial material (

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

MPC-D 100/1201) from the Nemegt locality of the

. The specimen has large openings on the top of the skull, a distinct frontoparietal suture, low and long infratemporal fenestrae, and a large, round eye socket. The forehead is notably rough, with multiple nodules on the lateral and posterior sides of 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 ...

bone. Paleontologists concluded that the specimen was an adult, despite the fact that the sutures are discernible and that it had a flat skull (a juvenile trait in many pachycephalosaurid species). In 2010, a study by Nick Longrich and colleagues suggested that flat-headed pachycephalosaurs were just juvenile forms of dome-headed adults, a view also supported by the earlier analysis of Horner and Goodwin in 2009. Longrich and colleagues suggested that ''Homalocephale'' is actually the juvenile or sub-adult stage of ''

'' mainly based on the lack of a dome and being discovered in the same locality (Nemegt) as the latter.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'', . David C. Evans and team in 2018 reported juvenile specimens of ''Prenocephale'' from the Nemegt Formation, noting a relatively linear growth in this pachycephalosaur characterized by a rounded dome. This differs from the flat skull of ''Homalocephale'' and given that even juvenile ''Prenocephale'' possessed a rather rounded dome, both taxa should be regarded as separate.

Description

''Homalocephale'' was about long.Holtz, Thomas R. Jr. (2008) ''Dinosaurs: The Most Complete, Up-to-Date Encyclopedia for Dinosaur Lovers of All Ages'
Supplementary Information
Unlike other definitely adult pachycephalosaurs (though similar to probable juvenile specimens referred to '' Dracorex'' and ''

Goyocephale ''Goyocephale'' is an extinct genus of pachycephalosaurian ornithischian that lived in Mongolia during the Late Cretaceous about 76 million years ago. It was first described in 1982 by Altangerel Perle, Teresa Maryańska and Halszka Osmólska f ...

''), ''Homalocephale'' sported a flat, wedge-shaped

skull roof The skull roof or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes, including land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In com ...

. Nonetheless, the surface of the skull was fairly thickened.

Classification

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 ...

from .

Paleobiology

''Homalocephale'' is also noted for having an unusually broad pelvis and some have suggested that the width served to protect vital organs from harm during flank-butting. Others think that they were for giving birth to live young. Instead of laying eggs. ''Homalocephale'' also had rather long legs, indicating a fast-moving gait.

References

Sources

*''Fantastic Facts About Dinosaurs'' ()

External links

Homalocephale
''dino-nakasato.org''

''leute.server.de'' {{Taxonbar, from=Q134134 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