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'''''Yarasuchus''''' (meaning "red crocodile") is an [[extinct]] [[genus]] of [[avemetatarsalia]]n [[archosaur]] that lived during the [[Anisian]] stage of the [[Middle Triassic]] of [[India]].<ref name=BS99>Bandyopadhyay, S. and Sengupta, D. P. (1999). Middle Triassic vertebrate faunas from India. ''[[Journal of African Earth Sciences]]'' '''29''': 233–241.</ref> The genus was named and described in 2005 from a collection of disarticulated but fairly complete fossil material found from the [[Middle Triassic]] [[Yerrapalli Formation]]. The material is thought to be from two individuals, possibly three, with one being much more complete and articulated than the other.<ref name="Sen, 2005">{{cite journal |last1=Sen |first1=Kasturi |title=A new rauisuchian archosaur from the Middle Triassic of India. |journal=[[Palaeontology (journal)|Palaeontology]] |volume=48 |issue=1 |date=2005 |doi=10.1111/j.1475-4983.2004.00438.x |pages=185–196 |doi-access=free }}</ref> The [[type species|type]] and only [[species]] is '''''Y. deccanensis'''''. ''Yarasuchus'' was a quadruped roughly {{Convert|2–2.5|m|feet}} long, with an elongated neck and tall spines on its vertebrae. Unlike other quadrupedal Triassic reptiles, the limbs and shoulders of ''Yarasuchus'' were slender, and more like those of [[ornithodira]]ns.
''Yarasuchus'' has had a complicated taxonomic history, after originally being described as a "[[Prestosuchidae|prestosuchid]] [[rauisuchia]]n", it was later variously recovered as a [[Poposauroidea|poposauroid]] [[pseudosuchia]]n and a non-archosaurian [[Archosauriformes|archosauriform]] of unstable position. In 2017 it was determined to be related to the similarly enigmatic Triassic reptiles ''[[Teleocrater]]'', ''[[Dongusuchus]]'' and ''[[Spondylosoma]].'' Together, they belong to a group called [[Aphanosauria]] and are placed at the base of Avemetatarsalia, sister to Ornithodira, making ''Yarasuchus'' one of the earliest diverging bird-line archosaurs known. The relative completeness of ''Yarasuchus'' and its evolutionary position helps to shed light on the origins of later, well known bird-line archosaurs such as the [[dinosaur]]s and [[pterosaur]]s.<ref name="Teleo">{{cite journal |last1=Nesbitt |first1=S.J. |last2=Butler |first2=R.J. |last3=Ezcurra |first3=M.D. |last4=Barrett |first4=P.M. |last5=Stocker |first5=M.R. |last6=Angielczyk |first6=K.D. |last7=Smith |first7=R.M H. |last8=Sidor |first8=C.A. |last9=Niedźwiedzki |first9=G. |last10=Sennikov |first10=A.G. |last11=Charig |first11=A.J. |title=The earliest bird-line archosaurs and the assembly of the dinosaur body plan |journal=Nature |volume=544 |issue=7651 |pages=484–487 |date=2017 |doi=10.1038/nature22037 |pmid=28405026 |bibcode=2017Natur.544..484N |url=http://pure-oai.bham.ac.uk/ws/files/39495711/Nesbitt_et_al._in_press.pdf }}</ref>
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===Skeleton===
[[File:Yarasuchus.jpg|thumb|left|Outdated life restoration depicting ''Yarasuchus'' as a "raisuchian" with osteoderms.]]
Almost the whole [[vertebral column]] is represented in ''Yarasuchus'', including at least 8 [[Cervical vertebrae|cervicals]] (including the [[Atlas (anatomy)|atlas]] and [[Axis (anatomy)|axis]]), 17 [[Thoracic vertebrae|dorsals]], 2 [[Sacral vertebra|sacral]], and at least 11 proximal [[Caudal vertebra|caudal]] vertebrae. The long neck of ''Yarasuchus'' is made up of a series of characteristically elongated cervical (neck) vertebrae, in contrast to its proportionately small skull. The articulating surfaces of the [[zygapophyses]] that connect between each vertebra are inclined and the [[Vertebral centrum|centra]] are strongly curved along the bottom margin with offset faces, indicating that the neck was held raised up from the body and arched along its length. The cervicals are uniquely characterised by a prominent midline keel that runs along the front half of the underside of each centrum, followed by two separate keels that continue to the rear edge.<ref name=NJKP07>{{cite journal |last1=Jalil |first1=Nour-Eddine |last2=Peyer |first2=Karin |year=2007 |title=A new rauisuchian (Archosauria, Suchia) from the Upper Triassic of the Argana Basin, Morocco |journal=[[Palaeontology (journal)|Palaeontology]] |volume=50 |issue=2 |pages=417–430 |doi=10.1111/j.1475-4983.2007.00640.x|doi-access=free }}</ref> The posterior [[cervical rib]]s have three heads, an unusual condition in archosaurs, and the corresponding cervicals possess an accessory articular facet to accommodate this.<ref name="Sen, 2005"/><ref name=Teleo/><ref name=":0"/><ref name=Teleo2/>
Unlike the cervicals, the dorsal (back) vertebra are short and compact, almost only half the length of the cervicals, as are the two sacral (hip) vertebra. The front-most two or three dorsal vertebra possess similar keels to the cervicals, unlike the condition in ''Teleocrater'' which has no keeled dorsals. The preserved proximal caudal (tail) vertebra are consistently elongate, however the distal caudals are missing and so the end of the tail is unknown. The vertebrae all have tall [[neural spines]] that run down the back, the tallest of which are over the hip where the spines are two times taller than the corresponding centra. The neck has similarly tall neural spines, however they are longer than tall and inclined forward so as to overhang the vertebra before it. The cervical neural spines are also unusually thickened and roughly textured at the top. The caudal neural spines are also tall and narrow, unlike the elongated centra, and are inclined backwards, decreasing in height further down the tail. The tall, broad neural spines were initially believed to be associated with rows of paramedian [[osteoderm]]s (although see below).<ref name="Sen, 2005" /><ref name=":0" />
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