''Homalocephale'' (from
Greek
Greek may refer to:
Greece
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 ...
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 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 ...
that lived during 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 ...
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, crocodilian ...
,
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, ...
, 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.
Biography
She was born in 1930 in Poznań. In 1949, she began to study biology at Faculty of Biology and Earth Scie ...
and
Teresa Maryańska
Teresa Maryańska (1937 – 3 October 2019) was a Polish paleontologist who specialized in Mongolian dinosaurs, particularly pachycephalosaurians and ankylosaurians. Peter Dodson (1998 p. 9) states that in 1974 Maryanska together with Halszka ...
, 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''.
Description
Adult ''Prenoceph ...
'', juvenile specimens of the latter indicate that they were distinct. ''Homalocephale'' was long and possibly herbivorous.
Discovery
![Homalocephale skull](https://upload.wikimedia.org/wikipedia/commons/e/ee/Homalocephale_skull.jpg)
The
type species
In 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 species that contains the biological type specimen ...
, ''H. calathocercos'', was described from an incomplete skull and postcranial material (
holotype
A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...
MPC-D 100/1201) from the Nemegt locality 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, crocodilian ...
. 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 The quadratojugal is a skull bone present in many vertebrates, including ...
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
Horner is an English and German surname that derives from the Middle English word for the occupation ''horner'', meaning horn-worker or horn-maker, or even horn-blower.
People
*Alison Horner (born 1966), British businesswoman
* Arthur Horner (dis ...
and Goodwin in 2009. Longrich and colleagues suggested that ''Homalocephale'' is actually the juvenile or sub-adult stage 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''.
Description
Adult ''Prenoceph ...
'' 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 NT small](https://upload.wikimedia.org/wikipedia/commons/4/49/Homalocephale_NT_small.jpg)
''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
''Pachycephalosaurus'' (; meaning "thick-headed lizard", from Greek ''pachys-/'' "thick", ''kephale/'' "head" and ''sauros/'' "lizard") is a genus of pachycephalosaurid dinosaurs. The type species, ''P. wyomingensis'', is the only known species, ...
'' 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 fo ...
''), ''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 and all land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium.
In comparati ...
. Nonetheless, the surface of the skull was fairly thickened.
[
]
Paleobiology
''Homalocephale'' is also noted for having an unusually broad pelvis, which lead some paleontologist
Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossi ...
s to suggest that the wide hips were for giving birth to live young. Others have suggested that the width served to protect vital organs from harm during flank-butting. ''Homalocephale'' also had rather long legs, indicating a fast-moving gait.
See also
* Timeline of pachycephalosaur research
This timeline of pachycephalosaur research is a chronological listing of events in the history of paleontology focused on the pachycephalosaurs, a group of dome-skulled herbivorous marginocephalian dinosaurs. One of the first major events related ...
References
*''Fantastic Facts About Dinosaurs'' ()
External links
* https://web.archive.org/web/20061006225059/http://www.dino-nakasato.org/en/special97/Homa-e.html
* https://web.archive.org/web/20070518001124/http://www.leute.server.de/frankmuster/H/Homalocephale.htm
{{Taxonbar, from=Q134134
Pachycephalosaurs
Late Cretaceous dinosaurs of Asia
Maastrichtian life
Nemegt fauna
Fossil taxa described in 1974
Taxa named by Teresa Maryańska
Taxa named by Halszka Osmólska
Ornithischian genera