Kentrosaurus: Difference between revisions

In the [[mandible]] (lower jaw), only an incomplete right dentary is known from ''Kentrosaurus''.<ref>Hennig, E. (1936). Ein dentale von Kentrurosaurus aethiopicus Hennig. ''Palaeontographica-Supplementbände'', 309-312.</ref> The deep dentary is almost identical in shape to that of ''Stegosaurus'', albeit much smaller. Similarly, the tooth is a typical stegosaurian tooth, small with a widened base and vertical grooves creating five ridges. The dentary has 13 preserved [[Dental alveolus|alveoli]] on the dorsomedial side and it they are slightly convex in lateral and dorsal views. On the surface adjacent to the alveoli, there is a shallow groove bearing small [[Vertebra|foramina]] (small openings in bone) that is similar to grooves on the dentary of the [[Cretaceous]] neornithischian ''[[Hypsilophodon]]'', with one foramina per tooth position. Stegosaurian teeth were small, triangular, and flat; wear facets show that they did grind their food.<ref name="FasWeis04">{{cite book |title=The Evolution and Extinction of the Dinosaurs |vauthors=Fastovsky DE, Weishampel DB |publisher=Cambridge University Press |year=2005 |isbn=978-0-521-81172-9 |veditors=Fastovsky DE, Weishampel DB |edition=2nd |pages=107–30 |chapter=Stegosauria: Hot Plates}}</ref> A single complete cheek tooth is preserved, with a large crown and long root. The crown notably has fewer marginal [[Denticle (tooth feature)|denticles]] and a prominent [[Cingulum (tooth)|cingulum]] compared to ''Stegosaurus'', ''Tuojiangosaurus'', and ''Huayangosaurus''.<ref name=":2" />

In Hennig's 1915 description, ''Kentrosaurus'' was assigned to the family [[Stegosauridae]] due to the preservation of dermal armor and features like posterodorsally angled neural spines on the caudal vertebrae.<ref name="Hennig1915" /> This is confirmed by modern [[cladistic]] analyses, although in 1915 Stegosauridae was a far more inclusive concept that included some taxa now classified as ankylosaurs. A consecutive narrowing down of this concept caused ''Kentrosaurus'', until the 1980s to be seen as a typical "primitive" stegosaurian,<ref name="Norman1985" /> to be placed in a more derived, higher, position in the stegosaur evolutionary tree. However, recent analyses have consistently found ''Kentrosaurus'' to be in Stegosauridae, though typically as one of the most basal genera in the family.<ref>{{Cite journal |last1=Hui |first1=Dai |last2=Ning |first2=Li |last3=Maidment |first3=Susannah C. R. |last4=Guangbiao |first4=Wei |last5=Yuxuan |first5=Zhou |last6=Xufeng |first6=Hu |last7=Qingyu |first7=Ma |last8=Xunqian |first8=Wang |last9=Haiqian |first9=Hu |last10=Guangzhao |first10=Peng |date=2022-03-30 |title=New stegosaurs from the Middle Jurassic Lower Member of the Shaximiao Formation of Chongqing, China |journal=Journal of Vertebrate Paleontology |volume=41 |issue=5 |pages=e1995737 |doi=10.1080/02724634.2021.1995737 |s2cid=247267743 |issn=0272-4634|doi-access=free }}</ref><ref name=":0" /><ref name=":1">{{Cite journal |last1=Raven |first1=Thomas J. |last2=Maidment |first2=Susannah C. R. |date=2017 |title=A new phylogeny of Stegosauria (Dinosauria, Ornithischia) |url=https://onlinelibrary.wiley.com/doi/10.1111/pala.12291 |journal=Palaeontology |language=en |volume=60 |issue=3 |pages=401–408 |doi=10.1111/pala.12291|bibcode=2017Palgy..60..401R |hdl=10044/1/45349 |s2cid=55613546 |hdl-access=free }}</ref> ''Kentrosaurus'' has many traits not seen in other stegosaurids but seen in basal stegosaurians, such as the presence of a parascapular spine and maxillary teeth with only seven denticles at the margin.<ref name="Galton1982" /><ref name="Galton1990" /> Cladogram of Stegosauria below that includes nearly every known stegosaur genus, recovering ''Kentrosaurus'' as a basal stegosaurid:<ref name=":1" />

<ref name=MallROM>{{cite journal|last=Mallison|first=H.|year=2010|title=CAD assessment of the posture and range of motion of ''Kentrosaurus aethiopicus'' HENNIG 1915|journal=[[Swiss Journal of Geosciences]]|volume=103|issue=2|pages=211–233|doi=10.1007/s00015-010-0024-2|s2cid=132746786|doi-access=free|bibcode=2010SwJG..103..211M }}</ref>