# Crurotarsi
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{{Short description|Clade of reptiles}}
{{Automatic taxobox
| name = Crurotarsans
| fossil_range =
[Early Triassic](/source/Early_Triassic)–[Present](/source/Holocene), {{Fossil range|248|0}}
| image = Protome_batalaria.jpg
| image_caption = Life restoration of ''[Protome batalaria](/source/Protome_batalaria)'', a [phytosaur](/source/phytosaur)
| image2 = Ornithosuchus_BW.jpg
| image2_caption = Life restoration of ''[Ornithosuchus woodwardi](/source/Ornithosuchus_woodwardi)'', a [pseudosuchian](/source/pseudosuchian) [archosaur](/source/archosaur)
| taxon = Crurotarsi
| authority = Sereno & Arcucci, 1990
| subdivision_ranks = Subgroups
| subdivision = * {{extinct}}''[Omosaurus](/source/Omosaurus)''
* {{extinct}}[Phytosauria](/source/Phytosauria)
*[Archosauria](/source/Archosauria)
** [Avemetatarsalia](/source/Avemetatarsalia)
** [Pseudosuchia](/source/Pseudosuchia)
}}
'''Crurotarsi''' is a [clade](/source/clade) of [archosauriform reptiles](/source/archosauriformes) that includes [crocodilia](/source/crocodilia)ns and stem-crocodilians and possibly bird-line [archosaurs](/source/Archosaur) too if the extinct, crocodile-like [phytosaur](/source/phytosaur)s are more distantly related to crocodiles than traditionally thought.[ Prior to 2011, the group had invariably included only archosaurs closer to crocodilians than to birds and other [dinosaurs](/source/Dinosaur). An equivalent term for the crocodilian side of the archosaur family tree is [Pseudosuchia](/source/Pseudosuchia). This traditional definition of Crurotarsi assumed that phytosaurs were [crown-group](/source/Crown_group) archosaurs and more closely related to crocodilians than to birds. However, a 2011 study argued that the phytosaur lineage evolved prior to the split between birds and crocodilians. This would mean that phytosaurs were not true archosaurs, and therefore could not be considered representatives of croc-line archosaurs.][{{cite journal|last= Sereno|first=Paul|year=1991|title=Basal archosaurs: phylogenetic relationships and functional implications|journal=Journal of Vertebrate Paleontology|volume=11 | issue = Suppl. 4|pages=1–51|doi=10.1080/02724634.1991.10011426 }}]
==Taxonomic history==
The name Crurotarsi was erected as a [node-based clade](/source/Cladistics) by [Paul Sereno](/source/Paul_Sereno) and A. B. Arcucci in 1990 to supplant the old term [Pseudosuchia](/source/Pseudosuchia), but with a different definition.[{{cite journal | last1 = Sereno | first1 = P.C. | last2 = Arcucci | first2 = A.B. | year = 1990 | title = The monophyly of crurotarsal archosaurs and the origin of bird and crocodile ankle joints | journal = Neues Jahrbuch für Geologie und Paläontologie, Abhandlungen | volume = 180 | pages = 21–52 }}] Crurotarsi includes, by most published definitions, all descendants of the common ancestor of modern [crocodile](/source/crocodile)s, [ornithosuchid](/source/Ornithosuchidae)s, [aetosaur](/source/aetosaur)s, and [phytosaur](/source/phytosaur)s; Nesbitt (2011) provided a shorter definition, defining Crurotarsi as "the least inclusive clade containing ''[Rutiodon carolinensis](/source/Rutiodon)'' Emmons, 1856, and ''[Crocodylus niloticus](/source/Nile_crocodile)'' Laurenti, 1768".[ According to two studies published in 2011 by Nesbitt and coworkers, using either of these definitions leads to the inclusion of all other true [archosaurs](/source/Archosauria) in Crurotarsi, due to the possibly [basal phylogenetic position](/source/Basal_(phylogenetics)) of the [phytosaur](/source/phytosaur)s. This means that grouping the phytosaurs and crocodilians into a clade while excluding the [avemetatarsalia](/source/avemetatarsalia)ns ([pterosaur](/source/pterosaur)s, [dinosaur](/source/dinosaur)s, and [bird](/source/bird)s) would result in a [paraphyletic grouping](/source/paraphyly). A more definitive group is [Pseudosuchia](/source/Pseudosuchia), which is defined as all archosaurs closer to crocodiles than to birds (matching the traditional content of Crurotarsi).][{{cite journal|last=Nesbitt|first=S.J.|year=2011|title=The early evolution of archosaurs: relationships and the origin of major clades|url=https://digitallibrary.amnh.org/handle/2246/6112|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}}][{{cite journal | last1 = Gauthier | first1 = J. A. | last2 = Nesbitt | first2 = S. J. | last3 = Schachner | first3 = E. R. | last4 = Bever | first4 = G. S. | last5 = Joyce | first5 = W. G. | year = 2011 | title = The bipedal stem-crocodilian ''Poposaurus gracilis'': inferring function in fossils and innovation in archosaur locomotion | journal = Bulletin of the Peabody Museum of Natural History | volume = 52 | pages = 107–126 | doi=10.3374/014.052.0102| s2cid = 86687464 }}]
==Phylogeny==
Paul Sereno and A. B. Arcucci named Crurotarsi in 1990, defining it as "[Parasuchia](/source/Parasuchia) [phytosaurs], [Ornithosuchidae](/source/Ornithosuchidae), ''[Prestosuchus](/source/Prestosuchus)'', Suchia, and all descendants of their common ancestor".[ The groups in this definition were considered crocodile-line archosaurs, as opposed to the bird-line archosaurs. Ornithosuchids were once considered bird-line archosaurs (as implied by their name, which means "bird crocodiles" in [Greek](/source/Greek_language)), but were later recognized as crocodile-line archosaurs. This reclassification may have inspired Sereno's Crurotarsi, a node-based clade defined by the inclusion of ornithosuchids and other early archosaurs.
Two names were proposed for crocodile-line archosaurs before Crurotarsi was erected. The first, Pseudosuchia, was established as a stem-based clade in 1985.][{{cite book |last=Gauthier |first=J.A. |author2=Padian, K. |year=1985 |chapter=Phylogenetic, functional, and aerodynamic analyses of the origin of birds and their flight |title=The Beginnings of Birds |editor=Hecht, M.K. |editor2=Ostrom, J.H. |editor3=Viohl, G. |editor4=Wellnhofer, P. |publisher=Freunde des Jura-Museums |location=Eichstatt |pages=185–197}}] It includes crocodiles and all archosaurs more closely related to crocodiles than to birds. The second, Crocodylotarsi, was named in 1988, possibly as a replacement for Pseudosuchia.[{{cite book |last=Benton |first=M.J. |author2=Clark, J.M. |year=1988 |chapter=Archosaur phylogeny and the relationships of the Crocodylia |title=Phylogeny and Classification of the Tetrapods |volume=1 |editor=Benton, M.J. |publisher=Clarendon Press |location=Oxford |pages=295–338}}] The name Pseudosuchia, meaning "false crocodiles", has been used for over a century, and traditionally included aetosaurs. As a clade, Pseudosuchia includes the group [Eusuchia](/source/Eusuchia), or "true crocodiles". Crocodylotarsi may have been named to remove confusion, but as a stem-based clade it is synonymous with Pseudosuchia. Because Pseudosuchia was named first, it has precedence. Crurotarsi traditionally contains the same archosaurs as Pseudosuchia, but as a node-based clade it is not synonymous.[{{cite journal |last=Brochu |first=C.A. |year=1997 |title=Synonymy, redundancy, and the name of the crocodile stem-group |journal=Journal of Vertebrate Paleontology |volume=17 |issue=2 |pages=448–449 |doi=10.1080/02724634.1997.10010992}}]
Below is a cladogram after Nesbitt & Norell (2006) and Nesbitt (2007) with Crurotarsi in its traditional sense encompassing just crocodile-line archosaurs:[{{cite journal | last1 = Nesbitt | first1 = SJ | last2 = Norell | first2 = MA. | year = 2006 | title = Extreme convergence in the body plans of an early suchian (Archosauria) and ornithomimid dinosaurs (Theropoda) | journal = Proceedings of the Royal Society of London B: Biological Sciences | volume = 273 | issue = 1590| pages = 1045–1048 | doi=10.1098/rspb.2005.3426 | pmid=16600879 | pmc=1560254}}][{{cite journal | last1 = Nesbitt | first1 = S. | year = 2007 | title = The anatomy of ''Effigia okeeffeae'' (Archosauria, Suchia), theropod-like convergence, and the distribution of related taxa | url = http://digitallibrary.amnh.org/dspace/bitstream/2246/5840/1/B302.pdf | journal = Bulletin of the American Museum of Natural History | volume = 302 | page = 84 | doi=10.1206/0003-0090(2007)302[1:taoeoa]2.0.co;2| hdl = 2246/5840 }}]
{{clade| style=font-size:90%;line-height:85%
|label1='''Archosauriformes'''
|1={{clade
|1=†''[Euparkeria](/source/Euparkeria)''80 px
|2={{clade
|1=†[Proterochampsidae](/source/Proterochampsidae)80 px
|label2=[Archosauria](/source/Archosauria)
|2={{clade
|1=to [Avemetatarsalia](/source/Avemetatarsalia)40 px
|label2='''Crurotarsi'''
|2={{clade
|1=†[Phytosauria](/source/Phytosauria)80px
|label2=[Suchia](/source/Suchia)
|2={{clade
|1=†[Aetosauria](/source/Aetosauria)80px
|2={{clade
|1='''[Crocodylomorpha](/source/Crocodylomorpha)'''80px
|2={{clade
|1=†[Ornithosuchidae](/source/Ornithosuchidae)80 px
|label2=[Rauisuchia](/source/Rauisuchia)
|2={{clade
|1={{clade
|1=†[Rauisuchidae](/source/Rauisuchidae)80px
|2=†[Prestosuchidae](/source/Prestosuchidae)80px}}
|label2="Group X"
|2={{clade
|1=†''[Arizonasaurus](/source/Arizonasaurus)''80px
|2={{clade
|1=†''[Lotosaurus](/source/Lotosaurus)''80px
|label2="Group Y" or [Shuvosaurinae](/source/Shuvosaurinae)
|2={{clade
|1=†''[Sillosuchus](/source/Sillosuchus)''
|2={{clade
|1=†''[Shuvosaurus](/source/Shuvosaurus)''80px
|2=†''[Effigia](/source/Effigia)''80px
}} }} }} }} }} }} }} }} }} }} }} }} }}
Cladogram after Brusatte, Benton, Desojo and Langer (2010):[{{cite journal | last1 = Brusatte | first1 = Stephen L. | last2 = Benton | first2 = Michael J. | last3 = Desojo | first3 = Julia B. | last4 = Langer | first4 = Max C. | year = 2010 | title = The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida) | journal = Journal of Systematic Palaeontology | volume = 8 | issue = 1| pages = 3–47| doi = 10.1080/14772010903537732 | s2cid = 59148006 | url = https://www.pure.ed.ac.uk/ws/files/8232155/PDF_Brusatteetal2010ArchosaurPhylogeny.pdf | hdl = 20.500.11820/24322ff3-e80e-45f2-8d53-d35fd104195c | hdl-access = free }}]
{{clade| style=font-size:90%;line-height:85%
|label1='''Archosauriformes'''
|1={{clade
|1=†''[Erythrosuchus](/source/Erythrosuchus)''80 px
|2={{clade
|1=†''[Euparkeria](/source/Euparkeria)''80 px
|2={{clade
|1=†[Proterochampsidae](/source/Proterochampsidae)80 px
|label2=[Archosauria](/source/Archosauria)
|2={{clade
|1=to [Avemetatarsalia](/source/Avemetatarsalia)40 px
|label2='''Crurotarsi'''
|2={{clade
|1=†[Phytosauria](/source/Phytosauria)80px
|label2=[Suchia](/source/Suchia)
|2={{clade
|1={{clade
|1=†[Aetosauria](/source/Aetosauria)80px
|label2=[Paracrocodylomorpha](/source/Paracrocodylomorpha)
|2={{clade
|1=†''[Gracilisuchus](/source/Gracilisuchus)''80 px
|label2=[Bathyotica](/source/Bathyotica)
|2={{clade
|1=†''[Erpetosuchus](/source/Erpetosuchus)''80 px
|2='''[Crocodylomorpha](/source/Crocodylomorpha)'''80px }} }} }}
|2={{clade
|1={{clade
|1=†''[Revueltosaurus](/source/Revueltosaurus)''
|2=†[Ornithosuchidae](/source/Ornithosuchidae)80 px }}
|label2=[Rauisuchia](/source/Rauisuchia)
|2={{clade
|label1=†'''[Rauisuchoidea](/source/Rauisuchoidea)'''
|1={{clade
|1={{clade
|1=''[Arganasuchus](/source/Arganasuchus)''
|2={{clade
|1=''[Fasolasuchus](/source/Fasolasuchus)''
|2={{clade
|1=''[Stagonosuchus](/source/Stagonosuchus)''
|2=''[Ticinosuchus](/source/Ticinosuchus)''80 px }} }} }}
|2={{clade
|label1=[Prestosuchidae](/source/Prestosuchidae)
|1={{clade
|1=''[Saurosuchus](/source/Saurosuchus)''80 px
|2={{clade
|1=''[Batrachotomus](/source/Batrachotomus)''
|2=''[Prestosuchus](/source/Prestosuchus)''80px }} }}
|label2=[Rauisuchidae](/source/Rauisuchidae)
|2={{clade
|1=''[Tikisuchus](/source/Tikisuchus)''
|2={{clade
|1=''[Rauisuchus](/source/Rauisuchus)''80px
|2={{clade
|1=''[Postosuchus](/source/Postosuchus)''80px
|2=''[Teratosaurus](/source/Teratosaurus)'' }} }} }} }} }}
|label2=†'''[Poposauroidea](/source/Poposauroidea)'''
|2={{clade
|1=''[Yarasuchus](/source/Yarasuchus)''
|2={{clade
|1=''[Qianosuchus](/source/Qianosuchus)''
|2={{clade
|1=''[Arizonasaurus](/source/Arizonasaurus)''80px
|2=''[Bromsgroveia](/source/Bromsgroveia)''
|3=''[Lotosaurus](/source/Lotosaurus)''80px
|4=''[Poposaurus](/source/Poposaurus)''80px
|5=''[Sillosuchus](/source/Sillosuchus)''
|label6='''Shuvosauridae'''
|6={{clade
|1=''[Shuvosaurus](/source/Shuvosaurus)''80px
|2=''[Effigia](/source/Effigia)''80px
}} }} }} }} }} }} }} }} }} }} }} }} }}
In 2011, Sterling J. Nesbitt found phytosaurs to be the sister taxon of Archosauria, and therefore not crocodile-line archosaurs. Because phytosaurs are included in the definition of Crurotarsi, this change in their [phylogenetic](/source/phylogenetic) placement expanded the scope of Crurotarsi, which therefore now includes phytosaurs, crocodiles, pterosaurs and dinosaurs. However, Pseudosuchia still contains only crocodile-line archosaurs.
Below is a [cladogram](/source/cladogram) modified from Nesbitt (2011) showing the new changes:[
{{clade| style=font-size:90%;line-height:85%
|label1=[Archosauriformes](/source/Archosauriformes)
|1={{clade
|1=†[Proterosuchidae](/source/Proterosuchidae)80 px
|2={{clade
|1=†[Erythrosuchidae](/source/Erythrosuchidae)80 px
|2={{clade
|1=†''[Vancleavea](/source/Vancleavea)''80 px
|2={{clade
|1=†[Proterochampsia](/source/Proterochampsia)80 px
|2={{clade
|1=†''[Euparkeria](/source/Euparkeria)''80 px
|label2='''Crurotarsi'''
|2={{clade
|1=†[Phytosauria](/source/Phytosauria)80px
|label2='''[Archosauria](/source/Archosauria)'''
|2={{clade
|1=[Avemetatarsalia](/source/Avemetatarsalia) (bird-line archosaurs)40 px
|label2=[Pseudosuchia](/source/Pseudosuchia) (crocodile-line archosaurs)
|2={{clade
|1=†[Ornithosuchidae](/source/Ornithosuchidae)80 px
|2=[Suchia](/source/Suchia)80px }} }} }} }} }} }} }} }} }}
==References==
{{Reflist|30em}}
*{{cite book|last=Benton|first=M. J.|title=Vertebrate Paleontology|year= 2004|edition=3rd|publisher=Blackwell Science|author-link=Michael Benton}}
*{{cite web|publisher=[Reuters](/source/Reuters)|date=2008-09-12|last=Dunham|first=W.|title=Lucky break allowed dinosaurs to rule Earth |url=http://uk.reuters.com/article/uk-dinosaurs-idUKN1128337120080911 |archive-url=https://web.archive.org/web/20170816233157/http://uk.reuters.com/article/uk-dinosaurs-idUKN1128337120080911 |url-status=dead |archive-date=August 16, 2017 |access-date=2012-01-14}}
*{{cite journal | last = Brusatte | first = S. L. | author2 = Benton, M. J. | author3 = Ruta, M. | author4 = Lloyd, G. T. | title = Superiority, Competition, and Opportunism in the Evolutionary Radiation of Dinosaurs | journal = [Science](/source/Science_(journal)) | volume = 321 | issue = 5895 | pages = 1485–1488 | date = 2008-09-12 | url = http://palaeo.gly.bris.ac.uk/Benton/reprints/2008Science.pdf | doi = 10.1126/science.1161833 | access-date = 2012-01-14 | pmid = 18787166 | s2cid = 13393888 | archive-url = https://web.archive.org/web/20140624204033/http://palaeo.gly.bris.ac.uk/Benton/reprints/2008Science.pdf | archive-date = 2014-06-24 | url-status = dead | hdl = 20.500.11820/00556baf-6575-44d9-af39-bdd0b072ad2b | hdl-access = free }}
==External links==
{{Wikispecies|Crurotarsi}}
*[https://web.archive.org/web/20050306102719/http://www.palaeos.com/Vertebrates/Units/270Archosauromorpha/270.510.html Palaeos]
*[https://web.archive.org/web/20081019121413/http://palaeo.gly.bris.ac.uk/benton/vertclass.html taxonomic hierarchy according to Benton 2004]
*[http://www.helsinki.fi/~mhaaramo/metazoa/deuterostoma/chordata/archosauria/pseudosuchia/crurotarsi.html Mikko's Phylogeny]
{{Archosauromorpha|B.}}
{{Taxonbar|from=Q131341}}
Category:Crurotarsans
Category:Archosauriformes
Category:Tetrapod unranked clades
Category:Triassic reptiles
Category:Extant Early Triassic first appearances
Category:Taxa named by Paul Sereno
---
Adapted from the Wikipedia article [Crurotarsi](https://en.wikipedia.org/wiki/Crurotarsi) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Crurotarsi?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.
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