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'''''Scleromochlus''''' (Greek for "hard fulcrum") is an [[extinct]] [[genus]] of small [[archosauriformes|archosauriform]] from the Late [[Triassic]] period. The genus contains the type and only species '''''Scleromochlus taylori''''', named by [[Arthur Smith Woodward]] in 1907.<ref name="woodward1907">{{cite journal | last1 = Woodward | first1 = A.S. | author-link = Arthur Smith Woodward | title = On a New Dinosaurian Reptile (''Scleromochlus Taylori'', gen. Et sp. Nov.) from the Trias of Lossiemouth, Elgin | journal = Quarterly Journal of the Geological Society | volume = 63 | issue = 1–4 | pages= 140–144 | year = 1907 | doi = 10.1144/GSL.JGS.1907.063.01-04.12 | url =https://www.biodiversitylibrary.org/item/114069#page/263/mode/1up}}</ref>
'''''Scleromochlus''''' (Greek for "hard fulcrum") is an [[extinct]] [[genus]] of small [[archosauriformes|archosauriform]] from the Late [[Triassic]] period. The genus contains the type and only species '''''Scleromochlus taylori''''', named by [[Arthur Smith Woodward]] in 1907.<ref name="woodward1907">{{cite journal | last1 = Woodward | first1 = A.S. | author-link = Arthur Smith Woodward | title = On a New Dinosaurian Reptile (''Scleromochlus Taylori'', gen. Et sp. Nov.) from the Trias of Lossiemouth, Elgin | journal = Quarterly Journal of the Geological Society | volume = 63 | issue = 1–4 | pages= 140–144 | year = 1907 | doi = 10.1144/GSL.JGS.1907.063.01-04.12 | s2cid = 131522263 | url =https://www.biodiversitylibrary.org/item/114069#page/263/mode/1up}}</ref>


==Discovery==
==Discovery==
Line 19: Line 19:


==Description==
==Description==
''Scleromochlus taylori'' was about {{convert|181|mm}} long, with long hind legs; it may have been capable of four-legged and two-legged locomotion. Studies about its gait suggest that it engaged in [[kangaroo]]- or [[springhare]]-like [[plantigrade]] hopping;<ref name=":0">{{Cite journal|last=Sereno|first=P.C.|last2=Arcucci|first2=A.B.|year=1994|title=Dinosaurian precursors from the Middle Triassic of Argentina: ''Marasuchus lilloensis'', gen. nov.|journal=Journal of Vertebrate Paleontology|volume=14|issue=1|pages=53–73|doi=10.1080/02724634.1994.10011538}}</ref><ref name="benton1999">{{cite journal | last1=Benton | first1=M.J. | author-link=Michael J. Benton | title=''Scleromochlus taylori'' and the origin of dinosaurs and pterosaurs| pages= 1423–1446 | year=1999 | volume=354 |pmc=1692658 | journal=Philosophical Transactions of the Royal Society B: Biological Sciences | doi = 10.1098/rstb.1999.0489 | jstor=57034 | issue=1388 }}</ref><ref>{{Cite book| title = Pterosaurs: Natural History, Evolution, Anatomy|last=Witton |first=M.P. |isbn=978-0691150611|year=2013|publisher=Princeton University Press }}</ref> however, a 2020 reassessment of ''Scleromochlus'' by Bennett suggested that it was a "sprawling quadrupedal hopper analogous to frogs."<ref name="bennett2020">{{Cite journal|last=Bennett|first=S.C.|year=2020|title=Reassessment of the Triassic archosauriform ''Scleromochlus taylori'': neither runner nor biped, but hopper|journal=PeerJ|volume=8|pages=e8418|doi=10.7717/peerj.8418|issn=2167-8359|doi-access=free}}</ref> If ''Scleromochlus'' is indeed related to [[pterosaurs]], this may offer insight as to how the latter evolved, since early pterosaurs also show adaptations for saltatorial locomotion.<ref>{{cite journal|doi=10.7717/peerj.1018|pmid=26157605|pmc=4476129|title=Were early pterosaurs inept terrestrial locomotors?|journal=PeerJ|volume=3|pages=e1018|year=2015|last1=Witton|first1=M.P.}}</ref>
''Scleromochlus taylori'' was about {{convert|181|mm}} long, with long hind legs; it may have been capable of four-legged and two-legged locomotion. Studies about its gait suggest that it engaged in [[kangaroo]]- or [[springhare]]-like [[plantigrade]] hopping;<ref name=":0">{{Cite journal|last1=Sereno|first1=P.C.|last2=Arcucci|first2=A.B.|year=1994|title=Dinosaurian precursors from the Middle Triassic of Argentina: ''Marasuchus lilloensis'', gen. nov.|journal=Journal of Vertebrate Paleontology|volume=14|issue=1|pages=53–73|doi=10.1080/02724634.1994.10011538}}</ref><ref name="benton1999">{{cite journal | last1=Benton | first1=M.J. | author-link=Michael J. Benton | title=''Scleromochlus taylori'' and the origin of dinosaurs and pterosaurs| pages= 1423–1446 | year=1999 | volume=354 |pmc=1692658 | journal=Philosophical Transactions of the Royal Society B: Biological Sciences | doi = 10.1098/rstb.1999.0489 | jstor=57034 | issue=1388 }}</ref><ref>{{Cite book| title = Pterosaurs: Natural History, Evolution, Anatomy|last=Witton |first=M.P. |isbn=978-0691150611|year=2013|publisher=Princeton University Press }}</ref> however, a 2020 reassessment of ''Scleromochlus'' by Bennett suggested that it was a "sprawling quadrupedal hopper analogous to frogs."<ref name="bennett2020">{{Cite journal|last=Bennett|first=S.C.|year=2020|title=Reassessment of the Triassic archosauriform ''Scleromochlus taylori'': neither runner nor biped, but hopper|journal=PeerJ|volume=8|pages=e8418|doi=10.7717/peerj.8418|pmid=32117608|pmc=7035874|issn=2167-8359|doi-access=free}}</ref> If ''Scleromochlus'' is indeed related to [[pterosaurs]], this may offer insight as to how the latter evolved, since early pterosaurs also show adaptations for saltatorial locomotion.<ref>{{cite journal|doi=10.7717/peerj.1018|pmid=26157605|pmc=4476129|title=Were early pterosaurs inept terrestrial locomotors?|journal=PeerJ|volume=3|pages=e1018|year=2015|last1=Witton|first1=M.P.}}</ref>


==Classification==
==Classification==
[[File:Scleromochlus taylori.jpg|thumb|Hypothetical skeletal diagram]]
[[File:Scleromochlus taylori.jpg|thumb|Hypothetical skeletal diagram]]
A lightly built [[cursorial]] animal, its [[phylogeny|phylogenetic]] position has been debated; as different analyses have found it to be either the [[basal (phylogenetics)|basal]]-most [[ornithodira]]n, the sister-taxon to [[Pterosauria]], or a basal member of [[Avemetatarsalia]] that lies outside of [[Ornithodira]]. In the phylogenetic analyses conducted by Nesbitt ''et al.'' (2017) ''Scleromochlus'' was recovered either as a basal member of [[Dinosauromorpha]] or as a non-[[aphanosauria]]n, non-pterosaur basal avemetatarsalian. However, the authors stressed that scoring ''Scleromochlus'' was challenging given the small size and poor preservation of the fossils, and stated that it could not be scored for many of the important characters that optimize near the base of Avemetatarsalia.<ref name="nesbitt2017">{{cite journal |first1=S.J. |last1=Nesbitt |first2=R.J. |last2=Butler |first3=M.D. |last3=Ezcurra |first4=P.M. |last4=Barrett |first5=M.R. |last5=Stocker |first6=K.D. |last6=Angielczyk |first7=R.M.H. |last7=Smith |first8=C.A. |last8=Sidor |first9=G. |last9=Niedźwiedzki |first10=A.G. |last10=Sennikov |first11=A.J. |last11=Charig |year=2017 |title=The earliest bird-line archosaurs and the assembly of the dinosaur body plan |journal=Nature |volume=544 |issue=7651 |pages=484–487 |doi=10.1038/nature22037 |url=http://pure-oai.bham.ac.uk/ws/files/39495711/Nesbitt_et_al._in_press.pdf |pmid=28405026}}</ref>
A lightly built [[cursorial]] animal, its [[phylogeny|phylogenetic]] position has been debated; as different analyses have found it to be either the [[basal (phylogenetics)|basal]]-most [[ornithodira]]n, the sister-taxon to [[Pterosauria]], or a basal member of [[Avemetatarsalia]] that lies outside of [[Ornithodira]]. In the phylogenetic analyses conducted by Nesbitt ''et al.'' (2017) ''Scleromochlus'' was recovered either as a basal member of [[Dinosauromorpha]] or as a non-[[aphanosauria]]n, non-pterosaur basal avemetatarsalian. However, the authors stressed that scoring ''Scleromochlus'' was challenging given the small size and poor preservation of the fossils, and stated that it could not be scored for many of the important characters that optimize near the base of Avemetatarsalia.<ref name="nesbitt2017">{{cite journal |first1=S.J. |last1=Nesbitt |first2=R.J. |last2=Butler |first3=M.D. |last3=Ezcurra |first4=P.M. |last4=Barrett |first5=M.R. |last5=Stocker |first6=K.D. |last6=Angielczyk |first7=R.M.H. |last7=Smith |first8=C.A. |last8=Sidor |first9=G. |last9=Niedźwiedzki |first10=A.G. |last10=Sennikov |first11=A.J. |last11=Charig |year=2017 |title=The earliest bird-line archosaurs and the assembly of the dinosaur body plan |journal=Nature |volume=544 |issue=7651 |pages=484–487 |doi=10.1038/nature22037 |url=http://pure-oai.bham.ac.uk/ws/files/39495711/Nesbitt_et_al._in_press.pdf |pmid=28405026|bibcode=2017Natur.544..484N }}</ref>


In 2020, Bennett interpreted ''Scleromochlus'' as possessing certain characteristics, including [[osteoderm]]s and a [[crurotarsal]] morphology of the ankle, which suggested that ''Scleromochlus'' was not closely related to ornithodirans. He instead argued for a position of ''Scleromochlus'' among the [[Doswelliidae]] or elsewhere among [[basal (phylogenetics)|basal]] members of the [[Archosauriformes]].<ref name="bennett2020"/>
In 2020, Bennett interpreted ''Scleromochlus'' as possessing certain characteristics, including [[osteoderm]]s and a [[crurotarsal]] morphology of the ankle, which suggested that ''Scleromochlus'' was not closely related to ornithodirans. He instead argued for a position of ''Scleromochlus'' among the [[Doswelliidae]] or elsewhere among [[basal (phylogenetics)|basal]] members of the [[Archosauriformes]].<ref name="bennett2020"/>

Revision as of 07:25, 14 October 2021

Scleromochlus
Temporal range: Late Triassic, Carnian
Cast of holotype specimen NHMUK R3556
Scientific classification Edit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Ornithodira
Clade: †Pterosauromorpha
Family: †Scleromochlidae
Huene, 1914
Genus: †Scleromochlus
Woodward, 1907
Species:
†S. taylori
Binomial name
†Scleromochlus taylori
Woodward, 1907

Scleromochlus (Greek for "hard fulcrum") is an extinct genus of small archosauriform from the Late Triassic period. The genus contains the type and only species Scleromochlus taylori, named by Arthur Smith Woodward in 1907.[1]

Discovery

Lithograph of the holotype

Its fossils have been found in the Carnian Lossiemouth Sandstone of Scotland. The holotype is BMNH R3556, a partial skeleton preserved as an impression in sandstone; part of the skull and tail are missing.[1]

Description

Scleromochlus taylori was about 181 millimetres (7.1 in) long, with long hind legs; it may have been capable of four-legged and two-legged locomotion. Studies about its gait suggest that it engaged in kangaroo- or springhare-like plantigrade hopping;[2][3][4] however, a 2020 reassessment of Scleromochlus by Bennett suggested that it was a "sprawling quadrupedal hopper analogous to frogs."[5] If Scleromochlus is indeed related to pterosaurs, this may offer insight as to how the latter evolved, since early pterosaurs also show adaptations for saltatorial locomotion.[6]

Classification

Hypothetical skeletal diagram

A lightly built cursorial animal, its phylogenetic position has been debated; as different analyses have found it to be either the basal-most ornithodiran, the sister-taxon to Pterosauria, or a basal member of Avemetatarsalia that lies outside of Ornithodira. In the phylogenetic analyses conducted by Nesbitt et al. (2017) Scleromochlus was recovered either as a basal member of Dinosauromorpha or as a non-aphanosaurian, non-pterosaur basal avemetatarsalian. However, the authors stressed that scoring Scleromochlus was challenging given the small size and poor preservation of the fossils, and stated that it could not be scored for many of the important characters that optimize near the base of Avemetatarsalia.[7]

In 2020, Bennett interpreted Scleromochlus as possessing certain characteristics, including osteoderms and a crurotarsal morphology of the ankle, which suggested that Scleromochlus was not closely related to ornithodirans. He instead argued for a position of Scleromochlus among the Doswelliidae or elsewhere among basal members of the Archosauriformes.[5]

References

  1. ^ a b Woodward, A.S. (1907). "On a New Dinosaurian Reptile (Scleromochlus Taylori, gen. Et sp. Nov.) from the Trias of Lossiemouth, Elgin". Quarterly Journal of the Geological Society. 63 (1–4): 140–144. doi:10.1144/GSL.JGS.1907.063.01-04.12. S2CID 131522263.
  2. ^ Sereno, P.C.; Arcucci, A.B. (1994). "Dinosaurian precursors from the Middle Triassic of Argentina: Marasuchus lilloensis, gen. nov". Journal of Vertebrate Paleontology. 14 (1): 53–73. doi:10.1080/02724634.1994.10011538.
  3. ^ Benton, M.J. (1999). "Scleromochlus taylori and the origin of dinosaurs and pterosaurs". Philosophical Transactions of the Royal Society B: Biological Sciences. 354 (1388): 1423–1446. doi:10.1098/rstb.1999.0489. JSTOR 57034. PMC 1692658.
  4. ^ Witton, M.P. (2013). Pterosaurs: Natural History, Evolution, Anatomy. Princeton University Press. ISBN 978-0691150611.
  5. ^ a b Bennett, S.C. (2020). "Reassessment of the Triassic archosauriform Scleromochlus taylori: neither runner nor biped, but hopper". PeerJ. 8: e8418. doi:10.7717/peerj.8418. ISSN 2167-8359. PMC 7035874. PMID 32117608.
  6. ^ Witton, M.P. (2015). "Were early pterosaurs inept terrestrial locomotors?". PeerJ. 3: e1018. doi:10.7717/peerj.1018. PMC 4476129. PMID 26157605.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  7. ^ Nesbitt, S.J.; Butler, R.J.; Ezcurra, M.D.; Barrett, P.M.; Stocker, M.R.; Angielczyk, K.D.; Smith, R.M.H.; Sidor, C.A.; Niedźwiedzki, G.; Sennikov, A.G.; Charig, A.J. (2017). "The earliest bird-line archosaurs and the assembly of the dinosaur body plan" (PDF). Nature. 544 (7651): 484–487. Bibcode:2017Natur.544..484N. doi:10.1038/nature22037. PMID 28405026.
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