archosauriformes

Early archosauriforms, informally termed "proterosuchians", were superficially crocodile-like animals with sprawling gaits, carnivorous habits, and long hooked snouts. Unlike the bulk of their therapsid contemporaries, archosauriforms survived the catastrophic end-Permian mass extinction. The Late Permian proterosuchid Archosaurus is similar in appearance to its Early Triassic relative, Proterosuchus. Within a few million years after the beginning of the Triassic, the archosauriformes had diversified past the "proterosuchian" grade. The next major archosauriform group was Erythrosuchidae, a family of apex predators with massive heads, the largest terrestrial carnivorous reptiles up to that time.

In 2016, Martin Ezcurra provided the name Eucrocopoda for the clade including all archosauriforms more crownward (closer to archosaurs) than erythrosuchids. He defined the clade all taxa more closely related to Euparkeria capensis, Proterochampa barrionuevoi, Doswellia kaltenbachi, Parasuchus hislopi, Passer domesticus (the house sparrow), or Crocodylus niloticus (the Nile crocodile) than to Proterosuchus fergusi or Erythrosuchus africanus. The name translates to "true crocodile feet", in reference to the possession of a crocodilian-style crurotarsal ankle.{{Cite journal|last=Ezcurra|first=Martín D.|date=2016-04-28|title=The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms|journal=PeerJ|language=en|volume=4|pages=e1778|doi=10.7717/peerj.1778|issn=2167-8359|doi-access=free|pmid=27162705|pmc=4860341}} Eucrocopodans include the families Euparkeriidae (small, agile reptiles),Proterochampsidae (narrow-snouted predators endemic to South America), and Doswelliidae (heavily armored Laurasian reptiles similar to proterochampsids), as well as various other strange reptiles such as Vancleavea and Asperoris.

The most successful archosauriforms, and the only members to survive into the Jurassic, were the archosaurs. Archosauria includes crocodilians, birds, and all descendants of their common ancestor. Extinct archosaurs include aetosaurs, rauisuchids (both members of the crocodilian branch), pterosaurs, and non-avian dinosaurs (both members of the avian branch).[https://books.google.com/books?id=TN_KBP3vxg4C&dq=No+non-archosaurian+%22archosauriforms+persist+beyond+the+Triassic%E2%80%94Jurassic+boundary%22&pg=PA582 Anatomy, Phylogeny and Palaeobiology of Early Archosaurs and Their Kin]

Vascular density and osteocyte density, shape and area have been used to estimate the bone growth rate of archosaurs, leading to the conclusion that this rate had a tendency to grow in ornithodirans and decrease in pseudosuchians.{{Cite journal|last1=Cubo|first1=Jorge|last2=Roy|first2=Nathalie Le|last3=Martinez-Maza|first3=Cayetana|last4=Montes|first4=Laetitia|date=2012 |title=Paleohistological estimation of bone growth rate in extinct archosaurs|url=https://www.cambridge.org/core/journals/paleobiology/article/paleohistological-estimation-of-bone-growth-rate-in-extinct-archosaurs/2F2B5C2B38EF97772E1D6D7ED3443553 |journal=Paleobiology|language=en|volume=38|issue=2|pages=335–349|doi=10.1666/08093.1|bibcode=2012Pbio...38..335C |s2cid=84303773|issn=0094-8373}} The same method also supports the existence of high resting metabolical rates similar to those of living endotherms (mammals and birds) in the Prolacerta-Archosauriformes clade that were retained by most subgroups, though decreased in Proterosuchus, Phytosauria and Crocodilia.{{Cite journal|last1=Legendre|first1=Lucas J.|last2=Guénard|first2=Guillaume|last3=Botha-Brink|first3=Jennifer|last4=Cubo|first4=Jorge|date=2016-11-01|title=Palaeohistological evidence for ancestral high metabolic rate in archosaurs |url=https://academic.oup.com/sysbio/article/65/6/989/2281633|journal=Systematic Biology|language=en|volume=65|issue=6|pages=989–996|doi=10.1093/sysbio/syw033|issn=1063-5157|doi-access=free|pmid=27073251}} Erythrosuchids and Euparkeria are basal archosauriforms showing signs of high growth rates and elevated metabolism, with Erythrosuchus possessing a rate similar of the fastest-growing dinosaurs. Sexual maturity in those Triassic taxa was probably reached quickly, providing advantage in a habitat with unpredictable variation from heavy rainfall to drought and high mortality. Vancleavea and Euparkeria, which show slower growth rates compared to Erythrosuchus, lived after the climatic stabilization. Early crown archosaurs possessed increased growth rates, which were retained by ornithodirans.{{Cite journal|last1=Botha-Brink|first1=Jennifer|last2=Smith|first2=Roger M. H.|date=2011-11-01|title=Osteohistology of the Triassic archosauromorphs Prolacerta, Proterosuchus, Euparkeria, and Erythrosuchus from the Karoo Basin of South Africa|journal=Journal of Vertebrate Paleontology|volume=31|issue=6|pages=1238–1254|doi=10.1080/02724634.2011.621797|bibcode=2011JVPal..31.1238B |s2cid=130744235|issn=0272-4634}} Ornithosuchians and poposaurs are stem-crocodilians that show high growth rates similar to those of basal archosauriforms.{{Cite journal|last1=de Ricqlès|first1=Armand|last2=Padian|first2=Kevin|last3=Knoll|first3=Fabien|last4=Horner|first4=John R.|date=2008-04-01|title=On the origin of high growth rates in archosaurs and their ancient relatives: Complementary histological studies on Triassic archosauriforms and the problem of a "phylogenetic signal" in bone histology|url=http://www.sciencedirect.com/science/article/pii/S0753396908000207|journal=Annales de Paléontologie|language=en|volume=94|issue=2|pages=57–76|doi=10.1016/j.annpal.2008.03.002|bibcode=2008AnPal..94...57D |issn=0753-3969}}

Developmental, physiological, anatomical and palaeontological lines of evidence indicate that crocodilians evolved from endothermic ancestors. Living crocodilians are ambush predators adapted to a semi-aquatic lifestyle that benefits from ectothermy due to the lower oxygen intake that allows longer diving time. The mixing of oxygenated and deoxygenated blood in their circulatory system is apparently an innovation that benefits ectothermic life. Earlier archosaurs likely lacked those adaptations and instead had completely separated blood as birds and mammals do.{{Cite journal|last1=Seymour|first1=Roger S.|last2=Bennett-Stamper|first2=Christina L.|last3=Johnston|first3=Sonya D.|last4=Carrier|first4=David R.|last5=Grigg|first5=Gordon C.|date=2004-11-01|title=Evidence for endothermic ancestors of crocodiles at the stem of archosaur evolution |journal=Physiological and Biochemical Zoology|volume=77|issue=6|pages=1051–1067|doi=10.1086/422766|issn=1522-2152|pmid=15674775|hdl=2440/1933|s2cid=10111065|url=https://espace.library.uq.edu.au/view/UQ:71147/UQ71147_OA.pdf|hdl-access=free}}{{Cite journal|last=Summers|first=Adam P.|date=April 2005|title=Warm-hearted crocs|journal=Nature|language=en|volume=434|issue=7035|pages=833–834|doi=10.1038/434833a|issn=1476-4687|pmid=15829945|bibcode=2005Natur.434..833S|s2cid=4399224|doi-access=free}} A similar process occurred in phytosaurs, which were also semi-aquatic.{{Cite web|title=Dinosaur Renaissance|url=https://www.scientificamerican.com/article/dinosaur-renaissance/|website=Scientific American|date=April 1975 |language=en|access-date=2020-05-03}}

The similarities between pterosaur, ornithischian and coelurosaurian integument suggest a common origin of thermal insulation (feathers) in ornithodirans at least 250 million years ago.{{Cite journal|last1=Yang|first1=Zixiao|last2=Jiang|first2=Baoyu|last3=McNamara|first3=Maria E.|last4=Kearns|first4=Stuart L.|last5=Pittman|first5=Michael|last6=Kaye|first6=Thomas G.|last7=Orr|first7=Patrick J.|last8=Xu|first8=Xing|last9=Benton|first9=Michael J.|date=January 2019|title=Pterosaur integumentary structures with complex feather-like branching|url=https://www.nature.com/articles/s41559-018-0728-7|journal=Nature Ecology & Evolution|language=en|volume=3|issue=1|pages=24–30|doi=10.1038/s41559-018-0728-7|issn=2397-334X|pmid=30568282|s2cid=56480710|hdl=1983/1f7893a1-924d-4cb3-a4bf-c4b1592356e9|hdl-access=free}}{{Cite journal|last1=Benton|first1=Michael J.|last2=Dhouailly|first2=Danielle|last3=Jiang|first3=Baoyu|last4=McNamara|first4=Maria|date=2019-09-01|title=The early origin of feathers|url=http://www.sciencedirect.com/science/article/pii/S0169534719301405|journal=Trends in Ecology & Evolution|language=en|volume=34|issue=9|pages=856–869|doi=10.1016/j.tree.2019.04.018|issn=0169-5347|pmid=31164250|s2cid=174811556 |hdl=10468/8068|hdl-access=free}} Erythrosuchids living in high latitudes might have benefited from some sort of insulation. If Longisquama was an archosauromorph, it could be associated with the origin of feathers.{{Cite journal|last1=Buchwitz|first1=Michael|last2=Voigt|first2=Sebastian|date=2012-09-01|title=The dorsal appendages of the Triassic reptile Longisquama insignis: reconsideration of a controversial integument type|journal=Paläontologische Zeitschrift|language=en|volume=86|issue=3|pages=313–331|doi=10.1007/s12542-012-0135-3|bibcode=2012PalZ...86..313B |s2cid=84633512|issn=1867-6812}}

Below is a cladogram from Nesbitt (2011):{{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-access=free|hdl=2246/6112|s2cid=83493714}}

{{clade| style=font-size:100%;line-height:85%

|label1=Archosauriformes

|1={{clade

|label1=Proterosuchidae

|1={{clade

|1=Archosaurus

|2=Proterosuchus80 px}}

|2={{clade

|1=Erythrosuchus80 px

|2={{clade

|1=Vancleavea80 px

|2={{clade

|label1=Proterochampsia

|1={{clade

|1=Tropidosuchus

|2=Chanaresuchus80 px}}

|2={{clade

|1=Euparkeria80 px

|label2=Crurotarsi

|2={{clade

|label1=Phytosauria*

|1={{clade

|1=Parasuchus

|2={{clade

|1=Smilosuchus80px

|2=Pseudopalatus}} }}

|label2=Archosauria

|2={{clade

|1=Pseudosuchia80px

|2=Avemetatarsalia40 px

}} }} }} }} }} }} }}

*Note: Phytosaurs were previously placed within Pseudosuchia, or crocodile-line archosaurs.}}

Below is a cladogram from Sengupta et al. (2017),{{cite journal |last1=Sengupta |first1=S.|last2=Ezcurra |first2=M.D.|last3=Bandyopadhyay |first3=S.|year=2017|title=A new horned and long-necked herbivorous stem-archosaur from the Middle Triassic of India|journal=Scientific Reports|volume=7|issue=1|pages=8366|doi=10.1038/s41598-017-08658-8|pmid=28827583|pmc=5567049|bibcode=2017NatSR...7.8366S }} based on an updated version of Ezcurra (2016) that reexamined all historical members of the "Proterosuchia" (a polyphyletic historical group including proterosuchids and erythrosuchids). The placement of fragmentary taxa that had to be removed to increase tree resolution are indicated by dashed lines (in the most derived position that they can be confidently assigned to). Taxa that are nomina dubia are indicated by the note "dubium". Bold terminal taxa are collapsed.

{{clade| style=font-size:80%;line-height:80%

|label1=Crocopoda

|1={{clade

|1=Allokotosauria80px

|2={{clade

|1=Rhynchosauria80px

|2={{clade

|1=Boreopricea funerea

|2={{clade

|1=Prolacertidae 80px

|2={{clade

|1=SAM-PK-591|state1=dashed

|2="Ankistrodon indicus" (dubium)|state2=dashed

|3="Blomosuchus georgii" (dubium)|state3=dashed

|4=Tasmaniosaurus triassicus

|label5=Archosauriformes

|5={{clade

|state1=dashed

|1={{clade

|label1x=Chasmatosuchus |state1=dashed

|1={{clade

|1=Chasmatosuchus magnus

|2=Chasmatosuchus rossicus

|3=Gamosaurus lozovskii

}}

}}

|2=Chasmatosuchus vjushkovi|state2=dashed

|3=Vonhuenia friedrichi|state3=dashed

|4=Proterosuchidae80px

|5={{clade

|1=Eorasaurus olsoni|state1=dashed

|2=Kalisuchus rewanensis|state2=dashed

|3=Fugusuchus hejiapanensis

|4={{clade

|1={{clade

|1=Sarmatosuchus otschevi

|2={{clade

|1=Cuyosuchus huenei

|2={{clade

|1=Erythrosuchidae80px

|label2=Eucrocopoda

|2={{clade

|1=Asperoris mnyama

|2=Dorosuchus neoetus

|3={{clade

|1=Euparkeria capensis80 px

|2={{clade

|label1=Proterochampsia

|1={{clade

|1=Doswelliidae80px

|2=Proterochampsidae80px}}

|label2=Archosauria

|2={{clade

|label1=Pseudosuchia

|1={{clade

|1=Phytosauria80px

|2=The rest of Pseudosuchia80px

}}

|label2=Avemetatarsalia

|2={{clade

|1=Aphanosauria80 px

|2=Ornithodira40 px}}

}} }} }} }} }} }} }} }} }} }} }} }} }} }} }} }}

• {{cite book

| first = J. A. | last = Gauthier | author-link = Jacques Gauthier | editor-last = Padian | editor-first = K.

| chapter = Saurischian monophyly and the origin of birds

| title = The Origin of Birds and the Evolution of Flight

| series = Memoirs of the California Academy of Sciences

| chapter-url = https://books.google.com/books?id=B1d0QgAACAAJ

| year = 1986 | volume = 8 | pages = 1–55 | publisher = California Academy of Sciences

| isbn = 978-0-940228-14-6}}

• {{Cite journal

| last = Gauthier | first = J. A. | author-link = Jacques Gauthier |author2=Kluge, A. G. |author3=Rowe, T. | title = Amniote phylogeny and the importance of fossils

| journal = Cladistics | volume = 4 | issue = 2 | pages = 105–209 | publisher = John Wiley & Sons | date = June 1988

| doi = 10.1111/j.1096-0031.1988.tb00514.x | pmid = 34949076 | url = https://deepblue.lib.umich.edu/bitstream/2027.42/73857/1/j.1096-0031.1988.tb00514.x.pdf | hdl = 2027.42/73857 | s2cid = 83502693 | hdl-access = free }}

{{Reflist}}

• [https://web.archive.org/web/20050409174045/http://www.palaeos.com/vertebrates/Units/270Archosauromorpha/270.400.html Paleos]
• [https://web.archive.org/web/20050310170659/http://www.fmnh.helsinki.fi/users/haaramo/Metazoa/Deuterostoma/Chordata/Reptilia/Archosauromorpha/Archosauriformes.htm Mikko's Phylogeny Archive]

{{Archosauromorpha|B.}}

{{Taxonbar|from=Q282487}}

Category:Lopingian first appearances

Category:Extant Permian first appearances

Category:Taxa named by Jacques Gauthier

Category:Taxa described in 1986