| Amtocephale | |
|---|---|
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| Speculative restoration | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Clade: | Dinosauria |
| Clade: | †Ornithischia |
| Clade: | †Pachycephalosauria |
| Family: | †Pachycephalosauridae |
| Subfamily: | †Pachycephalosaurinae |
| Genus: | †Amtocephale Watabe, Tsogtbaatar & Sullivan,2011 |
| Species | |
Amtocephale is agenus ofpachycephalosauriddinosaur from earlyLate Cretaceous (Cenomanian-Coniacian stages) deposits of southernGobi Desert,Mongolia.
Amtocephale is known from theholotypeMPC-D 100/1203, a nearly completefrontoparietal dome of a subadult individual. It was collected from theBaynshire Formation at theAmtgai locality.Amtocephale was first named by Mahito Watabe, Khishigjaw Tsogtbaatar and Robert M. Sullivan in2011 and thetype species isAmtocephale gobiensis. The generic name combines a reference to the Amtgai site with a Greek κεφαλή,kephale, "head". Thespecific name refers to the provenance from the Gobi.
Amtocephale was assigned to thePachycephalosauridae and is perhaps the oldest pachycephalosaurid known, depending on the exact age of the formation.[1]
Paleontological expeditions of the Hayashibara Museum of Natural Sciences with theMongolian Paleontological Center into theGobi Desert began in 1993, surveying and prospecting in over 50 localities. The Amtgai locality, an outcrop of fossil beds within small cliffs, was excavated in 1993, 1994, 2001 and 2004. This small bed of less than 20 m (66 ft) of exposedsandstone andmudstone is part of theBaynshire Formation, where the HMNS and MPC collectedvertebrae and limb bones ofornithopods,turtle skulls and shells, several specimens of thetheropodSegnosaurus, and the skull of apachycephalosaur.[2] This single partial subadult skull ofAmtocephale from theBaynshire Formation, MPC-D 100/1203, was described by Japanese paleontologist Mahito Watabe, Mongolian paleontogist Khishigjaw Tsogtbaatar, and American paleontologistRobert M. Sullivan in2011 as the new taxonAmtocephale gobiensis. Thegenus name is a combination of the Amtgai locality and theAncient Greek word κεφαλή (cephalo) for "head", while thespecies name is a reference to the Gobi Desert of Mongolia where it was found.[1]
The age of the Baynshire Formation is poorly constrained, correlated to some stage of the earlyLate Cretaceous between theCenomanian and the Santonian, though it has even been found to be as young as theCampanian (~80.6 mya). Review of the land-vertebrate faunas of Mongolia has been inconclusive as the fauna are not distinctive, but as it is from the Baynshire FormationAmtocephale would correlate with a "Baynshirenian" age. The vertebrates of the Baynshire Formation suggest the Amtgai locality is no younger than the Santonian (83.5 mya) but it may be slightly older. This makesAmtocephale approximately the same age as the fauna of theMilk River Formation ofAlberta.[1] RecentcalciteU–Pb measurements performed by Kurumada and colleagues in 2020 have estimated the age of the Baynshire Formation between 95.9 ± 6.0 Ma and 89.6 ± 4.0 Ma, corresponding to theCenomanian-Coniacian stages,[3] which supportsAmtocephale as the oldest knownpachycephalosaurid.[1]
The frontoparietal dome, formed by a fusion of thefrontals in front and theparietals in the back, has a length of 53.2 millimetres (2.09 in) and a maximal thickness of 19 millimetres (0.75 in). The contribution to the dome length of the parietal part is exceptionally large, with a portion of 41%.[1]
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