Sinocephale

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Sinocephale
Temporal range: Late Cretaceous, 92  Ma
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Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Dinosauria
Clade:† Ornithischia
Clade:† Neornithischia
Clade:† Pachycephalosauria
Family:† Pachycephalosauridae
Subfamily:† Pachycephalosaurinae
Genus:† Sinocephale
Evans et al., 2021
Type species
†Troodon bexelli
Synonyms

Sinocephale (meaning "Chinese head") is a genus of pachycephalosaurid dinosaur that lived in Inner Mongolia, China during the Cretaceous period. The only species, Sinocephale bexelli, was originally named as a species of the genus Troodon in 1953, and later transferred to the genus Stegoceras . After decades of being considered dubious, it was re-evaluated in 2021 and recognized as a valid taxon, being given a unique generic name. The original holotype was lost, with modern research conducted using rediscovered plaster casts. Scant material makes for limited knowledge of its life appearance, but it is distinguished by an embayment on the back of the domed skull, which would give it a heart shape as seen from above. It is potentially the oldest known pachycephalosaurid and falls within the subset of the family called Pachycephalosaurinae, related to animals such as Pachycephalosaurus and Prenocephale . The geologic context of the species has been historically unclear but it is currently thought to originate in rocks belonging to the Ulansuhai Formation.

Contents

Discovery and naming

Mounts of Stegoceras, a genus Sinocephale has been associated with for much of its history Royal Tyrrell Museum Stegoceras.jpg
Mounts of Stegoceras , a genus Sinocephale has been associated with for much of its history

During the early 20th century, Swedish palaeontological expeditions were conducted in China; during one such expedition, sometime in 1930 or 1931, a specimen was discovered that would become recognized as the first evidence of Pachycephalosauria from Asia. It consisted of a parietal bone, largely complete along its midline and right side but missing part of the left. Discovered at the Tsondolien-Khuduk geologic locality in Inner Mongolia, the specimen among others were brought to Sweden for study in Uppsala. [1] The specimen was named and described by palaeontologist Birger Bohlin in 1953, as a new species of the genus Troodon, with the specific name T. bexelli, in honour of Gerhard Bexel, who discovered the specimen. [1] [2] The genus Troodon had historically been considered a pachycephalosaur rather than a theropod as is recognized today. [3] By the time the paper had been published the specimen had already been returned to China's Institute of Vertebrate Paleontology and Paleoanthropology; sometime subsequent to this return the specimen among with many others were lost. [1] A decade later in 1964 Oskar Kuhn reassigned T. bexelli to the genus Stegoceras as the species S. bexelli. [4]

Bohlin's species was largely ignored in the years subsequent to its original naming, [1] only occasionally invoked to mention its significance as the first known Asian pachycephalosaur. [5] [6] In 1983 Hans-Dieter Sues and Peter Galton commented on the species in a paper focused on North American pachycephalosaurs, noting that based on the data from Bohlin's description the species clearly differs from definite Stegoceras material, casting doubt on its assignment to the genus. They considered the material to clearly be indeterminate and unidentifiable as a valid taxon below the family level. [3] Robert M. Sullivan would agree with this sentiment in later papers, noting it likely belonged to Asian genus like Prenocephale but that it should be considered an undiagnostic nomen dubium . [7] [8] In her chapter on pachycephalosaurs in the 1990 book The Dinosauria , Teresa Maryańska offered an alternative opinion, noting points of anatomical distinctiveness compared to other pachycephalosaurids despite the scant nature of its material. She noted it would be worthwhile for the material to be re-examined and given its own genus. [1] [9]

Canadian paleontologist David Evans, lead author of the study that restudied and named Sinocephale David Evans.jpg
Canadian paleontologist David Evans, lead author of the study that restudied and named Sinocephale

Further research became possible with the recognition of two plaster casts of the holotype. One is located at the American Museum of Natural History under the specimen number AMNH 2073, and the other at the Museum of Evolution of Uppsala University under the specimen number PMU 23186, with the former having a tag indicating its origination in Uppsala. These are thought to have been made by Eric Ingemar Ståhl during the original period of study, before the return of the original specimen to China. These were used as plastotypes for the species, meaning they function as stand-ins for the holotype (which was never given a specimen number) due to it being lost; the holotype remains the name-bearing specimen and is not considered replaced. In light of this discovery palaeontologist David Evans and colleagues redescribed the species; they noted that, based on how the specimen had been discussed in the literature, they were potentially the first people since Bohlin to study the anatomy firsthand instead of merely basing opinions off of the 1953 paper. They aimed to provide a more in-depth description than the 1953 study, investigating the ornamentation and age of the animal and evaluating its phylogenetic place in the Pachycephalosauridae in light of the decades of discoveries since its naming. Finding the specimen to be a diagnostic, distinct species within the family, they gave it a new genus name, Sinocephale. The prefix refers to China, where the specimen was found, and the suffix -cephale means "head" and is a common suffix for pachycephalosaur names. [1]

There have been multiple interpretations of the geologic providence the Tsondolien-Khuduk locality where the holotype was found. [1] Bohlin thought that the species "is at least not older than the North American forms", referring to taxa such as Stegoceras, though noted the geology was likely not deposited at the exact same time. [2] In 1974 Maryańska and Halszka Osmólska tentatively favored the idea that Tsondelien-Khuduk was equivalent in age to the Djadochta Formation, which they considered Coniacian or Santonian in age. They noted this would make it the oldest known pachycephalosaur from Asia, with others then otherwise only known from the later Barun Goyot and Nemegt Formations. [5] The Djadochta Formation is now considered more recent than it was at the time, dating to the mid Campanian age. [10] Sues and Galton considered the stratigraphic placement of the Tsondolien-Khuduk locality uncertain, but noted it may be older than Djadochta rather than equivalent. They stated it was located in the Gansu region of China. [3] In The Dinosauria David Weishampel ascribed the rocks to the Minhe Formation, [9] something followed by later authors. [1] The redescription noted both of these were in error; the specimen is from Nei Mongol (Inner Mongolia), not Kansu, and so cannot be from Minhe. Through interpretation of the 1953 paper, map analysis, and firsthand understanding of the area by You Hailu (one of the four authors of the paper), they concluded that Sinocephale hails from the Ulansuhai Formation. The age of this formation is not constrained with confidence; it is definitely younger than the Cenomanian and is most likely Turonian in age. This makes Sinocephale the oldest known pachycephalosaurid genus in the world, [1] making it older than Acrotholus by at least 8 million years.

Description

Parietal dome of a pachycephalosaur (Foraminacephale) Prenocephale brevis.jpg
Parietal dome of a pachycephalosaur ( Foraminacephale )

Pachycephalosaurs were small bipedal animals bearing thickened skulls with a dome shape on their tops. [9] Among pachycephalosaurs, the most distinctive anatomical trait and sole autapomorphy, or trait unique to a specific species, of Sinocephale is the prominent embayment on the back of the parietal (fused left and right parietals). This would have given the skull a roughly heart-shaped profile when seen from above. Beyond this, a unique combination of traits variously found in other species also contributes to distinguishing the taxon. The parietal is widely exposed on the back of the head, differing from taxa like Stegoceras and Prenocephale which have large squamosals enclosing the parietal, and being similar to the condition seen in Foraminacephale and some species of Sphaerotholus . Unlike other taxa sharing this condition, however, it is lacking in prominent ornamentation along this parieto-squamosal shelf. Instead, ornamentation on the back of the skull seems to have been restricted to smooth, small irregular bumps and rugosities, which are common among pachycephalosaurs. Its parietal anatomy is overall an intermediate half-step between the straight morphology seen in Stegoceras and kin as opposed to more derived genera like Sphaerotholus with rounded shapes. On the front margin of the parietal, its connection to the frontal bone is also documented, with a thick undulating line of contact between the two bones. Though the apex of the skull is not preserved, the thickness of the preserved portion indicates the presence of a dome similar to other pachycephalosaurs. The temporal chamber is large and noticeably arched when viewed from the side. The only known specimen is hypothesized to constitute a subadult or adult, but with only plaster casts to study, this conclusion is tentative. [1]

Classification

Life restoration of the closely related Prenocephale Prenocephale bickering.jpg
Life restoration of the closely related Prenocephale
Skulls of fellow pachycephalosaurine Pachycephalosaurus Pachycephalosaurus ontogeny skulls - Museum of the Rockies - 2013-07-08.jpg
Skulls of fellow pachycephalosaurine Pachycephalosaurus
Flat-topped skull of Goyocephale, a more basal pachycephalosaur Goyocephalebcn1.JPG
Flat-topped skull of Goyocephale, a more basal pachycephalosaur

The taxon has been recognized as a member of the Pachycephalosauridae ever since its initial description in 1953, when the group was still known as Troodontidae. [2] [3] [5] The 2021 redescription was the first time Sinocephale was tested in a phylogenetic analysis; this analysis was modified from that of Woodruff et al. (2021), which itself is derived from that of Evans et al. 2013. [1] [11] [12] S. bexelli was able to be coded for 18% of the anatomical traits considered by the analysis. It was found that the species belonged to the Pachycephalosaurinae. This makes it quite distantly related to Stegoceras, despite its association with the genus historically, instead being related to animals like Prenocephale. It was cautioned, however, that the support for its phylogenetic position was not robust, and so subject to change. The phylogenetic tree of Evans et al. (2021) is reproduced below: [1]

Related Research Articles

<span class="mw-page-title-main">Pachycephalosauria</span> Extinct clade of dinosaurs

Pachycephalosauria is a clade of ornithischian dinosaurs. Along with Ceratopsia, it makes up the clade Marginocephalia. With the exception of two species, most pachycephalosaurs lived during the Late Cretaceous Period, dating between about 85.8 and 66 million years ago. They are exclusive to the Northern Hemisphere, all of them being found in North America and Asia. They were all bipedal, herbivorous/omnivorous animals with thick skulls. Skulls can be domed, flat, or wedge-shaped depending on the species, and are all heavily ossified. The domes were often surrounded by nodes and/or spikes. Partial skeletons have been found of several pachycephalosaur species, but to date no complete skeletons have been discovered. Often isolated skull fragments are the only bones that are found.

<i>Pachycephalosaurus</i> Genus of pachycephalosaurid dinosaurs

Pachycephalosaurus is a genus of pachycephalosaurid ornithischian dinosaur. The type species, P. wyomingensis, is the only known species, but some researchers argue that Stygimoloch might be a second species, P. spinifer, or a juvenile specimen of P. wyomingensis. It lived during the Maastrichtian age of the Late Cretaceous period in what is now western North America. Remains have been excavated in Montana, South Dakota, Wyoming, and Alberta. The species is known mainly from a single skull, plus a few extremely thick skull roofs. More complete fossils would come to be found in the following years.

<i>Stegoceras</i> Genus of pachycephalosaurid dinosaurs

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 described in 1902, and the type species Stegoceras validum was based on these remains. The generic name means "horn roof", and the specific name means "strong". Several other species have been placed in the genus over the years, but these have since been moved to other genera or deemed junior synonyms. Currently only S. validum and S. novomexicanum, named in 2011 from fossils found in New Mexico, remain. The validity of the latter species has also been debated.

<i>Homalocephale</i> Extinct genus of dinosaurs

Homalocephale is a genus of pachycephalosaurid dinosaur that lived during the Late Cretaceous period of what is now the Nemegt Formation, Mongolia, about 70 million years ago. The genus was described in 1974 by Halszka Osmólska and Teresa Maryańska, and consists of a single species, H. calathocercos. Though Homalocephale has been regarded as a synonym of Prenocephale, juvenile specimens of the latter indicate that they were distinct. Homalocephale was 1.8 m (5.9 ft) long and possibly a omnivore.

<i>Prenocephale</i> Extinct genus of dinosaurs

Prenocephale 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.

<i>Micropachycephalosaurus</i> Extinct genus of dinosaurs

Micropachycephalosaurus is an extinct genus of basal marginocephalian dinosaur containing only the type species, Micropachycephalosaurus hongtuyanensis. It lived in China during the Late Cretaceous (Campanian) and was found in the Jiangjunding Formation.

<i>Tylocephale</i> Extinct genus of dinosaurs

Tylocephale is a genus of pachycephalosaurid dinosaur, a group of dome-headed, herbivorous ornithischians, that lived during the Late Campanian stage of the Late Cretaceous in what is now Mongolia. It is known from a partial skull and associated mandible that were unearthed in 1971 by a Polish-Mongolian Expedition to the Barun Goyot Formation of the Gobi Desert. The specimen was described in 1974 by Polish paleontologists Teresa Maryańska and Halszka Osmólska as a new genus and species.

<i>Colepiocephale</i> Extinct genus of dinosaurs

Colepiocephale is a genus of pachycephalosaurid dinosaur from Late Cretaceous deposits of Alberta, Canada. It was collected from the Foremost Formation. The type species, C. lambei, was originally described by Sternberg, and later renamed by Sullivan in 2003. C. lambei is a domed pachycephalosaur characterized principally by the lack of a lateral and posteriosquamosal shelf, a steeply down-turned parietal, and the presence of two incipient nodes tucked under the posterior margin of the parietosquamosal border.

<i>Goyocephale</i> Extinct genus of dinosaurs

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 for a disarticulated skeleton with most of a skull, part of the forelimb and hindlimb, some of the pelvic girdle, and some vertebrae. Perle et al. named the remains Goyocephale lattimorei, from the Mongolian гоё (goyo), meaning "decorated", and the Ancient Greek κεφαλή (kephale), for head. The species name honours Owen Lattimore.

<i>Hanssuesia</i> Extinct genus of dinosaurs

Hanssuesia is a genus of pachycephalosaurid dinosaurs from the late Cretaceous period. It lived in what is now Alberta and Montana, and contains the single species Hanssuesia sternbergi.

<i>Sphaerotholus</i> Extinct genus of pachycephalosaur dinosaurs

Sphaerotholus is a genus of pachycephalosaurid dinosaur from the Upper Cretaceous of the western United States and Canada. To date, five species have been described: the type species, S. goodwini, from the Den-na-zin Member of the Kirtland Formation of San Juan County, New Mexico, USA; S. buchholtzae, from the Hell Creek Formation of western Carter County, Montana, USA and the Frenchman Formation of Saskatchewan, Canada; S. edmontonensis, from the Horseshoe Canyon Formation of Alberta, Canada; S. lyonsi, from the Dinosaur Park Formation (Campanian) of Alberta, Canada; and S. triregnum from the Hell Creek Formation of Garfield County, Montana, USA.

<i>Gravitholus</i> Extinct genus of dinosaurs

Gravitholus was a genus of pachycephalosaurid dinosaur from the late Cretaceous period. It was a pachycephalosaur, and like other pachycephalosaurids the skull roof formed a thick dome made of dense bone, which may have been used in head-butting contests over mates or territory. It lived in what is now Alberta, Canada, and was described in 1979 by W. P. Wall and Peter Galton. The type species is Gravitholus albertae.

Heishansaurus, meaning "Heishan lizard" after the area in China where it was discovered, is the name given to a dubious genus of herbivorous ornithischian dinosaur, probably belonging to the Ankylosauridae.

<i>Alaskacephale</i> Extinct genus of dinosaurs

Alaskacephale is an extinct genus of pachycephalosaurid, a group of dome-headed, herbivorous ornithischian dinosaurs, that lived during the Campanian stage of the Late Cretaceous period in what is now northern Alaska. The genus is one of the few known Arctic dinosaurs and was found in the Prince Creek Formation, which preserves a menagerie of fossils. The only known specimen, a squamosal bone, was found in 1999 and later described in 2005. However, Alaskacephale was not formally named until the next year.

<i>Texacephale</i> Extinct genus of dinosaurs

Texacephale is a pachycephalosaurid dinosaur from the Campanian stage of the Late Cretaceous. Its fossils come from the Aguja Formation of Big Bend National Park, in Texas, and were described in 2010 by Longrich, Sankey and Tanke. The generic name means Texas + "head" in reference to its place of discovery, and the specific name langstoni honors Wann Langston.

<i>Foraminacephale</i> Extinct genus of dinosaurs

Foraminacephale is a genus of pachycephalosaurid dinosaur from Late Cretaceous deposits of Canada.

<i>Acrotholus</i> Extinct genus of dinosaurs

Acrotholus is an extinct genus of pachycephalosaur dinosaur that lived during the Santonian of the late Cretaceous, in the Milk River Formation of Canada. The type species, A. audeti, was named after Roy Audet allowing access to his ranch leading to the discovery of the species. The discovery of this specimen lead to several new revelations in the fossil records questioning the preservation of small-bodied organisms along with the evolution of early pachycephalosaurs. The iconic cranial dome found on Acrotholus makes it one of the earliest indisputable known members of the pachycephalosaur family.

<span class="mw-page-title-main">Timeline of pachycephalosaur research</span> The progression of pachycephalosaur research over time

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 to the history of pachycephalosaur research actually regards the discovery of an unrelated dinosaur called Troodon, reported from the western United States by Joseph Leidy in 1856. The type specimen of Troodon was simply an unusual tooth, but the close resemblance between Troodon teeth and pachycephalosaur teeth would cause taxonomic confusion for over a century. This was resolved by Phil Currie in 1987, who realized that Troodon belonged to a group of bird-like carnivores then known as saurornithoidids, but since renamed Troodontidae after Troodon itself. The first scientifically documented true pachycephalosaur remains were discovered in Early Cretaceous rocks from England and named Stenopelix not long after Troodon was named in America. Other notable early finds include the well-known pachycephalosaur Stegoceras validum.

References

  1. 1 2 3 4 5 6 7 8 9 10 11 12 Evans, David; Brown, Caleb M.; You, Hailu; Campione, Nicolás E. (2021). "Description and revised diagnosis of Asia's first recorded pachycephalosaurid, Sinocephale bexelli gen. nov., from the Upper Cretaceous of Inner Mongolia, China". Canadian Journal of Earth Sciences. 58 (10): 981–992. Bibcode:2021CaJES..58..981E. doi:10.1139/cjes-2020-0190. S2CID   244227050.
  2. 1 2 3 Bohlin, B., (1953). Fossil reptiles from Mongolia and Kansu. Reports from the Scientific Expedition to the North-western Provinces of China under Leadership of Dr. Sven Hedin. VI. Vertebrate Palaeontology 6. ##The Sino-Swedish Expedition Publication. 37:1–113
  3. 1 2 3 4 Sues, H. D. & Galton, P. M. (1987). "Anatomy and classification of the North American Pachycephalosauria (Dinosauria: Ornithischia)". Palaeontographica Abteilung A. 198: 1–40.
  4. ↑ Kuhn, O., (1964), Fossilium Catalogus I: Animalia Pars 105. Ornithischia (Supplementum I), IJsel Pers, Deventer, 80 pp
  5. 1 2 3 Maryańska T, Osmólska H (1974). "Pachycephalosauria, a new suborder of ornithischian dinosaurs". Palaeontologica Polonica. 30: 45–102.
  6. ↑ Zhiming, Dong (1977). "A pachycephalosaur from the Wangshi Fm. of Laiyang Co., Shandong Province, Micropachycephalosaurus hongtuyanensis gen. et sp. nov". Vertebrata PalAsiatica. 16 (4).
  7. ↑ Sullivan, Robert M. (2000). "Prenocephale edmontonensis (Brown and Schlaikjer) new comb. and P. brevis (Lambe) new comb.(Dinosauria: Ornithischia: Pachycephalosauria) from the Upper Cretaceous of North America". Dinosaurs of New Mexico: Bulletin. 17: 177–190.
  8. ↑ 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.
  9. 1 2 3 Maryanska, T. (1990). Pachycephalosauria. In The Dinosauria. 1st ed. Edited by D.B. Weishampel, P. Dodson, and H. Osmólska. University of California Press, Berkeley, Calif. pp. 564–577.
  10. ↑ Dashzeveg, D.; Dingus, L.; Loope, D. B.; Swisher III, C. C.; Dulam, T.; Sweeney, M. R. (2005). "New Stratigraphic Subdivision, Depositional Environment, and Age Estimate for the Upper Cretaceous Djadokhta Formation, Southern Ulan Nur Basin, Mongolia" (PDF). American Museum Novitates (3498): 1−31. doi:10.1206/0003-0082(2005)498[0001:NSSDEA]2.0.CO;2. hdl: 2246/5667 . S2CID   55836458.
  11. ↑ Woodruff, D. Cary; Goodwin, Mark B.; Lyson, Tyler R.; Evans, David C (2021). "Ontogeny and variation of the pachycephalosaurine dinosaur Sphaerotholus buchholtzae, and its systematics within the genus". Zoological Journal of the Linnean Society. 193 (2): 563–601. doi:10.1093/zoolinnean/zlaa179.
  12. ↑ Evans, David C.; Schott, Ryan K.; Larson, Derek W.; Brown, Caleb M.; Ryan, Michael J. (2013-05-07). "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 . ISSN   2041-1723. PMID   23652016.
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