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{{Short description|Extinct genus of mammaliamorphs}}
{{italic title}}
{{Automatic taxobox
{{Automatic taxobox
| taxon = Stereognathus
| fossil_range = [[Bathonian]], {{fossil range|167.7|165.7}}
| fossil_range = [[Bathonian]]-[[Barremian]]?, {{fossil range|167.7|165.7|latest=Barremian}}
⚫
| authority = Charlesworth, 1854
| image = StereognathusooliticusToothOwen1857.png
| image_caption = The postcanine tooth of ''Stereognathus ooliticus'', from Owen 1857.
| type_species = '''''Stereognathus ooliticus'''''
| type_species = '''''Stereognathus ooliticus'''''
| type_species_authority = Charlesworth, 1854
| type_species_authority = Charlesworth, 1854
| subdivision_ranks = Species
| subdivision_ranks = Potential species
| subdivision = {{bold species list
| subdivision =
* '''''S. chuannanensis''''' <small>(He & Cai, 1984; originally ''[[Polistodon]]'')</small>
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|{{extinct}}S. ooliticus|Charlesworth, 1854
* '''''S. kolossovi''''' <small>(Lopatin & Agadjanian, 2008; originally ''[[Xenocretosuchus]]'')</small>
⚫
|{{extinct}}S. hebridicus|Waldman & Savage, 1972}}
* '''''S. kuwajimaensis''''' <small>(Matsuoka ''et al.'', 2016; originally ''[[Montirictus]]'')</small>
* '''''S. sibiricus''''' <small>(Tatarinov & Mashenko, 1999; originally ''[[Xenocretosuchus]]'')</small>
| synonyms =
⚫
* '''''S. hebridicus'''''? <small>Waldman & Savage, 1972</small>
}}
}}


'''''Stereognathus''''' is a genus of [[Tritylodontidae|tritylodont]] [[Therapsida|therapsids]] from the [[Bathonian]] ([[Middle Jurassic]]) of the [[United Kingdom]].<ref name="FossilworksStereognathus">Fossilworks. "Stereognathus." Retrieved from [http://fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=39216]</ref> It is known from two species, ''S. ooliticus'', the type species, and ''S. hebridicus'', known from a total of nine different localities in the United Kingdom.<ref name="FossilworksStereognathus" /> It was originally described as a crown [[Mammalia|mammal]],<ref name="FossilworksStereognathus" /> and its placement as a non-mammalian therapsid is still uncertain.<ref name="PalaeosStereognathus">Palaeos. "Cynodontia: Tritylodontidae." Retrieved from [http://palaeos.com/vertebrates/cynodontia/tritylodontidae.html]</ref>
'''''Stereognathus''''' is an extinct genus of [[Tritylodontidae|tritylodontid]] [[cynodont]]s from the [[Middle Jurassic]] of the [[United Kingdom]].<ref name="FossilworksStereognathus">[http://www.fossilworks.org/cgi-bin/bridge.pl?a=taxonInfo&taxon_no=39216 Fossilworks. "Stereognathus." Retrieved from]</ref> There is a single named species: ''S. ooliticus'', named after the [[Great Oolite]] deposits of England. A second species, ''S. hebridicus'', was named after the [[Hebrides]] in Scotland, where it was found; it was synonymized with ''S. ooliticus'' in 2017.<ref name="2017lump">{{cite journal | last1 = Panciroli | first1 = E. | last2 = Walsh | first2 = S. | last3 = Fraser | first3 = N.C. | last4 = Brusatte | first4 = S.L. | last5 = Corfe | first5 = I. | title = A reassessment of the postcanine dentition and systematics of the tritylodontid ''Stereognathus'' (Cynodontia, Tritylodontidae, Mammaliamorpha), from the Middle Jurassic of the United Kingdom | journal = Journal of Vertebrate Paleontology |volume=37 |issue=5 | page = e1351448 | date = 2017 | doi = 10.1080/02724634.2017.1351448 | doi-access = free | hdl = 20.500.11820/b140e841-1ad5-4cbe-aad7-7bb588f9f0c1 | hdl-access = free }}</ref>

==Discovery and naming==

''S. ooliticus'' was the first tritylodontid species ever found, being described by Charlesworth in 1855<ref>Charlesworth, E 1855. Reprint British Association. 1854 Liverpool Abstracts, 80.</ref> and later by Sir Richard Owen.<ref>Owen, R 1856 On the affinity of Stereognathus ooliticus (Charlesworth) a mammal from the Oolitic slate of Stonesfield . Quarterly Journal of the Geological Society of London, 13, 1-11.</ref> In 1972, ''S. hebridicus'' was named from several postcanine teeth recovered in [[Bathonian]] age deposits on the [[Isle of Skye]] in Scotland by palaeontologists [[R. J. G. Savage]] and Michael Waldman.<ref>Waldman, M and Savage, R.J.G 1972 [http://jgs.lyellcollection.org/content/128/2/119.full.pdf The first Jurassic mammal from Scotland]. Journal of the Geological Society of London 128:119-125</ref>
Despite being the first tritylodontid genus found and named, ''Stereognathus'' remains poorly represented, being known mainly from isolated molar teeth. There is, however, one holotype fragment of maxilla with three damaged molars, and a second fragment of maxilla with four sets of molar roots.

In 2017, Elsa Panciroli and colleagues found no points of variance between the anatomy of ''S. ooliticus'' and ''S. hebridicus'', accounting for changes with growth, which makes ''S. hebridicus'' a [[synonym (taxonomy)|junior synonym]] of ''S. ooliticus''.<ref name="2017lump"/> Also in 2017, Alexander Averianov and colleagues considered species of ''[[Polistodon]]'', ''[[Xenocretosuchus]]'', and ''[[Montirictus]]'' to be within the genus ''Stereognathus''; they also retained ''S. hebridicus'' as a separate species.<ref name="averianov2017">{{cite journal |first1=A.O. |last1=Averianov |first2=T. |last2=Martin |first3=A.V. |last3=Lopatin |first4=J.A. |last4=Schultz |first5=P.P. |last5=Skutschas |first6=S. |last6=Rico |first7=S.A. |last7=Krasnolutskii |year=2017 |title=A tritylodontid synapsid from the Middle Jurassic of Siberia and the taxonomy of derived tritylodontids |journal=Journal of Vertebrate Paleontology |volume=37 |issue=5 |pages=e1363767 |doi=10.1080/02724634.2017.1363767 }}</ref> However, this would mean ''Stereognathus'' persisted almost unchanged for over 60 million years across the whole of Eurasia, which would be very unusual. The issue remains unresolved.


==References==
==References==
{{Reflist}}
{{Reflist}}


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{{Cynodontia|P.}}
[[Category:Therapsids]]
{{Taxonbar|from=Q15299040}}
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[[Category:Jurassic synapsids]]

[[Category:Cynodonts]]
[[Category:Prehistoric synapsids of Europe]]
[[Category:Tritylodontids]]
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[[Category:Middle Jurassic synapsids of Europe]]
{{therapsid-stub}}
[[Category:Fossil taxa described in 1854]]



{{paleo-cynodont-stub}}
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{{Cynodontia|C.}}

Latest revision as of 14:09, 29 June 2024

Stereognathus
Temporal range: Bathonian-Barremian?, 167.7–165.7 Ma
↓
The postcanine tooth of Stereognathus ooliticus, from Owen 1857.
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Synapsida
Clade: Therapsida
Clade: Cynodontia
Family: †Tritylodontidae
Genus: †Stereognathus
Charlesworth, 1854
Type species
Stereognathus ooliticus
Charlesworth, 1854
Potential species
  • S. chuannanensis (He & Cai, 1984; originally Polistodon)
  • S. kolossovi (Lopatin & Agadjanian, 2008; originally Xenocretosuchus)
  • S. kuwajimaensis (Matsuoka et al., 2016; originally Montirictus)
  • S. sibiricus (Tatarinov & Mashenko, 1999; originally Xenocretosuchus)
Synonyms
  • S. hebridicus? Waldman & Savage, 1972

Stereognathus is an extinct genus of tritylodontid cynodonts from the Middle Jurassic of the United Kingdom.[1] There is a single named species: S. ooliticus, named after the Great Oolite deposits of England. A second species, S. hebridicus, was named after the Hebrides in Scotland, where it was found; it was synonymized with S. ooliticus in 2017.[2]

Discovery and naming

[edit]

S. ooliticus was the first tritylodontid species ever found, being described by Charlesworth in 1855[3] and later by Sir Richard Owen.[4] In 1972, S. hebridicus was named from several postcanine teeth recovered in Bathonian age deposits on the Isle of Skye in Scotland by palaeontologists R. J. G. Savage and Michael Waldman.[5] Despite being the first tritylodontid genus found and named, Stereognathus remains poorly represented, being known mainly from isolated molar teeth. There is, however, one holotype fragment of maxilla with three damaged molars, and a second fragment of maxilla with four sets of molar roots.

In 2017, Elsa Panciroli and colleagues found no points of variance between the anatomy of S. ooliticus and S. hebridicus, accounting for changes with growth, which makes S. hebridicus a junior synonym of S. ooliticus.[2] Also in 2017, Alexander Averianov and colleagues considered species of Polistodon, Xenocretosuchus, and Montirictus to be within the genus Stereognathus; they also retained S. hebridicus as a separate species.[6] However, this would mean Stereognathus persisted almost unchanged for over 60 million years across the whole of Eurasia, which would be very unusual. The issue remains unresolved.

References

[edit]
  1. ^ Fossilworks. "Stereognathus." Retrieved from
  2. ^ a b Panciroli, E.; Walsh, S.; Fraser, N.C.; Brusatte, S.L.; Corfe, I. (2017). "A reassessment of the postcanine dentition and systematics of the tritylodontid Stereognathus (Cynodontia, Tritylodontidae, Mammaliamorpha), from the Middle Jurassic of the United Kingdom". Journal of Vertebrate Paleontology. 37 (5): e1351448. doi:10.1080/02724634.2017.1351448. hdl:20.500.11820/b140e841-1ad5-4cbe-aad7-7bb588f9f0c1.
  3. ^ Charlesworth, E 1855. Reprint British Association. 1854 Liverpool Abstracts, 80.
  4. ^ Owen, R 1856 On the affinity of Stereognathus ooliticus (Charlesworth) a mammal from the Oolitic slate of Stonesfield . Quarterly Journal of the Geological Society of London, 13, 1-11.
  5. ^ Waldman, M and Savage, R.J.G 1972 The first Jurassic mammal from Scotland. Journal of the Geological Society of London 128:119-125
  6. ^ Averianov, A.O.; Martin, T.; Lopatin, A.V.; Schultz, J.A.; Skutschas, P.P.; Rico, S.; Krasnolutskii, S.A. (2017). "A tritylodontid synapsid from the Middle Jurassic of Siberia and the taxonomy of derived tritylodontids". Journal of Vertebrate Paleontology. 37 (5): e1363767. doi:10.1080/02724634.2017.1363767.


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