Crocodylomorpha

File:Hesperosuchus BW.jpg, a so-called "sphenosuchian"|330x330px]]

The earliest lineages of Crocodylomorpha are placed into the paraphyletic "Sphenosuchia", which are characterized by slender bodies with elongate legs. The oldest known crocodylomorph is Trialestes, known from the Late Triassic (Carnian-Norian) of Argentina, around 231–225 million years ago,{{Cite journal |last1=Irmis |first1=Randall B. |last2=Nesbitt |first2=Sterling J. |last3=Sues |first3=Hans-Dieter |date=January 2013 |title=Early Crocodylomorpha |url=https://www.lyellcollection.org/doi/10.1144/SP379.24 |journal=Geological Society, London, Special Publications |language=en |volume=379 |issue=1 |pages=275–302 |doi=10.1144/SP379.24 |bibcode=2013GSLSP.379..275I |issn=0305-8719|url-access=subscription }} the last groups of "sphenosuchians" persisted until the end of the Jurassic. During the Jurassic, crocodylomorphs diversified, including the emergence of herbivorous and omnivorous forms,{{Cite journal |last1=Melstrom |first1=Keegan M. |last2=Irmis |first2=Randall B. |date=July 2019 |title=Repeated Evolution of Herbivorous Crocodyliforms during the Age of Dinosaurs |journal=Current Biology |language=en |volume=29 |issue=14 |pages=2389–2395.e3 |doi=10.1016/j.cub.2019.05.076|pmid=31257139 |doi-access=free |bibcode=2019CBio...29E2389M }} as well as the aquatically adapted Neosuchia and Thalattosuchia, with Thalattosuchia and several groups of neosuchians becoming adapted to a marine lifestyle over the Jurassic and Cretaceous{{Cite journal |last1=Wilberg |first1=Eric W. |last2=Turner |first2=Alan H. |last3=Brochu |first3=Christopher A. |date=2019-01-24 |title=Evolutionary structure and timing of major habitat shifts in Crocodylomorpha |journal=Scientific Reports |language=en |volume=9 |issue=1 |page=514 |doi=10.1038/s41598-018-36795-1 |issn=2045-2322 |pmc=6346023 |pmid=30679529|bibcode=2019NatSR...9..514W }} During the Cretaceous, the Notosuchia were a diverse group across the Southern Hemisphere occupying many diverse ecologies.{{Cite journal |last1=Stubbs |first1=Thomas L. |last2=Pierce |first2=Stephanie E. |last3=Elsler |first3=Armin |last4=Anderson |first4=Philip S. L. |last5=Rayfield |first5=Emily J. |last6=Benton |first6=Michael J. |date=2021-03-31 |title=Ecological opportunity and the rise and fall of crocodylomorph evolutionary innovation |journal=Proceedings of the Royal Society B: Biological Sciences |language=en |volume=288 |issue=1947 |doi=10.1098/rspb.2021.0069 |issn=0962-8452 |pmc=8059953 |pmid=33757349}} Modern crocodilians, a subgroup of Neosuchia, emerged during the Late Cretaceous. Crocodylomorph diversity was severely reduced by the end-Cretaceous extinction event. The last group of terrestrially adapted crocodylomorphs was the Sebecidae, a group of large predatory notosuchians which persisted in South America until the middle Miocene around 12 million years ago.{{Cite journal |last1=Martin |first1=Jeremy E. |last2=Pochat-Cottilloux |first2=Yohan |last3=Laurent |first3=Yves |last4=Perrier |first4=Vincent |last5=Robert |first5=Emmanuel |last6=Antoine |first6=Pierre-Olivier |date=2022-10-28 |title=Anatomy and phylogeny of an exceptionally large sebecid (Crocodylomorpha) from the middle Eocene of southern France |url=https://www.tandfonline.com/doi/full/10.1080/02724634.2023.2193828 |journal=Journal of Vertebrate Paleontology |language=en |volume=42 |issue=4 |doi=10.1080/02724634.2023.2193828 |bibcode=2022JVPal..42E3828M |issn=0272-4634|url-access=subscription }}

Historically, all known living and extinct crocodiles were indiscriminately lumped into the order Crocodilia. However, beginning in the late 1980s, many scientists began restricting the order Crocodilia to the living species and close extinct relatives such as Mekosuchus. The various other groups that had previously been known as Crocodilia were moved to Crocodylomorpha and the slightly more restrictive Crocodyliformes.{{cite journal | last1 = Martin | first1 = J.E. | last2 = Benton | first2 = M.J. | year = 2008 | title = Crown Clades in Vertebrate Nomenclature: Correcting the Definition of Crocodylia | journal = Systematic Biology | volume = 57 | issue = 1| pages = 173–181 | doi=10.1080/10635150801910469 | pmid=18300130| doi-access = free }} Crocodylomorpha has been given the rank of superorder in some 20th and 21st century studies.{{Cite journal | last1 = Parrilla-Bel | first1 = J. | last2 = Young | first2 = M. T. | last3 = Moreno-Azanza | first3 = M. | last4 = Canudo | first4 = J. I.|editor1-link=Richard J. Butler | editor1-last = Butler | editor1-first = Richard J | title = The First Metriorhynchid Crocodylomorph from the Middle Jurassic of Spain, with Implications for Evolution of the Subclade Rhacheosaurini | doi = 10.1371/journal.pone.0054275 | journal = PLOS ONE | volume = 8 | issue = 1 | pages = e54275 | year = 2013 | pmid = 23372699| pmc = 3553084| bibcode = 2013PLoSO...854275P | doi-access = free }}

The old Crocodilia was subdivided into the suborders:

• Eusuchia: true crocodiles (which includes crown-group Crocodylia)
• Mesosuchia: 'middle' crocodiles
• Thalattosuchia: sea crocodiles
• Protosuchia: first crocodiles
• Sphenosuchia: wedge crocodiles
• Sebecosuchia: Sebecus crocodiles

Mesosuchia is a paraphyletic group as it does not include eusuchians (which nest within Mesosuchia). Mesoeucrocodylia was the name given to the clade that contains mesosuchians and eusuchians (Whetstone and Whybrow, 1983).

The previous definitions of Crocodilia and Eusuchia did not accurately convey evolutionary relationships within the group. The only order-level taxon that is currently considered valid is Crocodilia in its present definition. Prehistoric crocodiles are represented by many taxa, but since few major groups of the ancient forms are distinguishable, a conclusion on how to define new order-level clades is not yet possible. (Benson & Clark, 1988). Crocodylomorpha in the modern sense, as defined by Paul Sereno in 2005, is phylogenetically defined as the most inclusive clade containing Crocodylus niloticus (the Nile crocodile), but not Rauisuchus tiradentes, Poposaurus gracilis, Gracilisuchus stipanicicorum, Prestosuchus chiniquensis, or Aetosaurus ferratus. {{cite journal|last=Nesbitt|first=S.J.|year=2011|title=The early evolution of archosaurs: relationships and the origin of major clades|journal=Bulletin of the American Museum of Natural History|volume=352|pages=1–292|doi=10.1206/352.1|hdl=2246/6112|s2cid=83493714|doi-access=free}}

Below is a cladogram of most known crocodylomorphs from Stephan F. Speikeman in 2023. The modern consensus is that "sphenosuchians" form a paraphyletic assemblage leading towards the more derived Crocodyliformes. The basal crocodylomorph Saltoposuchidae was defined by Speikman, 2023 as the most inclusive clade containing Saltoposuchus connectens, but not Sphenosuchus acutus, Carnufex carolinensis, and Trialestes romeri. The clade Solidocrania was established by Alexander A. Ruebenstahl and colleagues in 2022 to unite crocodyliforms with their closest "sphenosuchian" relatives who both share similarly reinforced skulls. This clade was defined as the least inclusive clade including Junggarsuchus sloani, Almadasuchus figarii, and Macelognathus vagans.{{cite journal |last1=Ruebenstahl |first1=A. A. |last2=Klein |first2=M. D. |last3=Yi |first3=H. |last4=Xu |first4=X. |last5=Clark |first5=J. M. |title=Anatomy and relationships of the early diverging Crocodylomorphs Junggarsuchus sloani and Dibothrosuchus elaphros |journal=The Anatomical Record |date=2022 |volume=305 |issue=10 |pages=2463–2556 |doi=10.1002/ar.24949|pmid=35699105 |pmc=9541040 }} {{clade|{{clade

|1=Erpetosuchus 80px

|2=Redondavenator

|3=Carnufex

|4=CM 73372

|5={{clade

|1={{clade

|1={{clade

|1=Trialestes

|2=Pseudohesperosuchus

}}

}}

|2={{clade

|label1=Saltoposuchidae

|1={{clade

|1=Saltoposuchus

|2={{clade

|1=Litargosuchus

|2=Terrestrisuchus

}}

}}

|2={{clade

|1=Hesperosuchus 80 px

|2={{clade

|1=Kayentasuchus

|2=Dromicosuchus

}}

}}

|3={{clade

|1=Sphenosuchus

|2={{clade

|1=Dibothrosuchus

|label2=Solidocrania

|2={{clade

|1=Junggarsuchus

|2={{clade

|label1=Hallopodidae

|1={{clade

|1=Almadasuchus

|2={{clade

|1=Macelognathus

|2=Hallopus

}}

}}

|2=Crocodyliformes 80px

}}

}}

}}

}}

}}

}}

}}|label1=Crocodylomorpha}}

The Crocodylomorpha comprise a variety of forms, shapes, and sizes, which occupied a range of habitats. As with most amniotes, Crocodylomorphs were and are oviparous, laying eggs in a nest or mound, known from strata as old as the Late Jurassic.{{cite journal |last1=Russo |first1=J. |last2=Mateus |first2=O. |last3=Marzola |first3=M. |last4=Balbino |first4=A. |year=2017 |title=Two new ootaxa from the late Jurassic: The oldest record of crocodylomorph eggs, from the Lourinhã Formation, Portugal |journal=PLOS One |volume=12 |issue=3 |pages=1–23 |doi=10.1371/journal.pone.0171919 |pmid=28273086 |pmc=5342183 |bibcode=2017PLoSO..1271919R |doi-access=free }}

Adult size varies widely, from about 55 cm long in Knoetschkesuchus to much larger dimensions, as in Sarcosuchus. Most crocodylomorphs were carnivores, but many lineages evolved to be obligate piscivores, such as the extant gharials.

In some forms, like Hesperosuchus and Terrestrisuchus, metatarsal V still had one or two phalanges,{{cite journal | doi=10.1002/spp2.1534 | title=A taxonomic revision and cranial description of Terrestrisuchus gracilis (Archosauria, Crocodylomorpha) from the Upper Triassic of Pant-y-Ffynnon Quarry (Southern Wales) | date=2023 | last1=Spiekman | first1=Stephan N. F. | last2=Fernandez | first2=Vincent | last3=Butler | first3=Richard J. | last4=Dollman | first4=Kathleen N. | last5=Maidment | first5=Susannah C. R. | journal=Papers in Palaeontology | volume=9 | issue=6 | doi-access=free | bibcode=2023PPal....9E1534S }} but in Crocodyliformes all metatarsal V phalanges have been lost.{{cite journal |last1=Spiekman |first1=Stephan N. F. |date=2023 |title=A revision and histological investigation of Saltoposuchus connectens (Archosauria: Crocodylomorpha) from the Norian (Late Triassic) of south-western Germany |url=https://academic.oup.com/zoolinnean/article/199/2/354/7204136 |journal=Zoological Journal of the Linnean Society |volume=199 |issue=2 |pages=354–391 |doi=10.1093/zoolinnean/zlad035 |via=Oxford Academic|doi-access=free }}

{{Reflist}}

• Benton, M. J. (2004), Vertebrate Palaeontology, 3rd ed. Blackwell Science Ltd
• Hay, O. P. 1930 (1929–1930). Second Bibliography and Catalogue of the Fossil Vertebrata of North America. Carnegie Institution Publications, Washington, 1, 990 pp.

• [https://web.archive.org/web/20170629120846/http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Crocodylomorpha/Index.html Crocodylomorpha] - webpages by Ross Elgin on the University of Bristol server
• [https://web.archive.org/web/20170629120841/http://palaeo.gly.bris.ac.uk/Palaeofiles/Fossilgroups/Crocodylomorpha/Groups.html Major subgroups] classification (used here)
• [https://web.archive.org/web/20071226224455/http://www.palaeos.com/Vertebrates/Units/Unit290/290.100.html#Crocodylomorpha Crocodylomorpha] from Palaeos
• [https://web.archive.org/web/20071226224455/http://www.palaeos.com/Vertebrates/Units/Unit290/290.100.html#Crocodylomorpha Technical definition]

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{{Crocs}}

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Category:Chordate superorders

Category:Extant Late Triassic first appearances

Category:Norian first appearances