Yarasuchus

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Yarasuchus
Temporal range: Middle Triassic, Anisian
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Clade: Archosauria
Clade: Avemetatarsalia
Clade:† Aphanosauria
Genus:† Yarasuchus
Sen, 2005
Type species
Yarasuchus deccanensis
Sen, 2005

Yarasuchus (meaning "red crocodile") is an extinct genus of avemetatarsalian archosaur that lived during the Anisian stage of the Middle Triassic of India. [1] 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. [2] The type and only species is Y. deccanensis. Yarasuchus was a quadruped roughly 2–2.5 metres (6.6–8.2 ft) 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 ornithodirans.

Contents

Yarasuchus has had a complicated taxonomic history, after originally being described as a "prestosuchid rauisuchian", it was later variously recovered as a poposauroid pseudosuchian and a non-archosaurian 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 dinosaurs and pterosaurs. [3]

Description

Yarasuchus was a relatively small, gracile, low-slung quadruped with a long neck and a small head, estimated to be around 2–2.5 metres (6.6–8.2 ft) long. [2] [4] Despite its appearance, Yarasuchus has a number of features in common with other avemetatarsalians, such as its elongated neck vertebrae. It has long, slender limb bones, unlike the more robust limbs of most pseudosuchians, but similar to other avemetatarsalians. Unlike later avemetatarsalians though, Yarasuchus has a "crocodile-normal" ankle configuration, more similar to pseudosuchians and some stem-archosaurs. Yarasuchus is very similar in appearance to its close relative Teleocrater, and differs in only a few minor anatomical features of the skeleton, such as having a less of a rear facing glenoid (the bony shoulder socket) than that of Teleocrater. [3]

Skull

The skull of Yarasuchus is poorly represented, known from only a few isolated pieces. A number of bones were initially identified by Sen (2005), including a jugal, quadrate and part of the quadratojugal, squamosal, both pterygoids and two maxilla that included a portion of premaxilla attached to one of them, as well as an associated tooth. [2] However both maxillae differ from the known maxilla in Teleocrater and instead more closely resemble those of an allokotosaur. Nesbitt and colleagues also regarded the jugal, quadrate and quadratojugal as indeterminate bones, and re-identified the squamosal as a postorbital belonging to a larger individual than the holotype specimen. As of 2017, the right postorbital and both pterygoids are the only positively identified cranial material belonging to Yarasuchus. [3]

Skeleton

Outdated life restoration depicting Yarasuchus as a "raisuchian" with osteoderms. Yarasuchus.jpg
Outdated life restoration depicting Yarasuchus as a "raisuchian" with osteoderms.

Almost the whole vertebral column is represented in Yarasuchus, including at least 8 cervicals (including the atlas and axis), 17 dorsals, 2 sacral, and at least 11 proximal 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 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. [5] The posterior cervical ribs have three heads, an unusual condition in archosaurs, and the corresponding cervicals possess an accessory articular facet to accommodate this. [2] [3] [4] [6]

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 osteoderms (although see below). [2] [4]

The pectoral (shoulder) girdle is delicately built, with a tall and slender scapula that is expanded distally and constricted near the glenoid. The scapula has a continuous acromion process, as well as an unusual sharp, thin ridge of bone running down its posterior margin, a feature only found in aphanosaurs and silesaurids. [3] The coracoid is small and rounded, and forms a down and rearward facing glenoid fossa with the scapula. The ilium of the pelvic (hip) girdle has a prominent posterior process and supraacetabular crest—a ridge of bone over the acetabulum. The acetabulum itself is relatively large and almost completely closed, unlike the fully open acetabulum of dinosaurs. The pubis is short and points downwards, with a thickened, flattened end. The ischium is very similar to that of Teleocrater, and is directed down and back from the hips, with a tapered shaft and slightly expanded distal end. [6] The pelvic girdle articulates with the spine via the sacral ribs, of which the first is larger and more robust. The nature of the articulation between the ilium and the sacral ribs suggests the hip was held sub-horizontally and faced ventrolaterally, causing the legs to be positioned down and outwards from the body. [2] [4]

The limb bones of Yarasuchus are characteristically slender. The humerus is long and cylindrical, with a moderately developed elongated deltopectoral crest that occupies roughly 30% of the length of the bone, similar to the condition in dinosaurs. The ulna is arched somewhat, and is roughly equal in length to the humerus. The femur is similarly gracile, and has a sigmoidal (s-shaped) curve along its length. The head of the femur is not turned in. A moderately developed fourth trochanter is placed proximally on the femur, unlike the well developed fourth trochanters of dinosaurs. The manus and pes are almost entirely missing, except for the calcaneus of the ankle joint. The calcaneus indicates that Yarasuchus had a "crocodile-normal" ankle, which allowed for more rotation of the foot than the derived hinge-like avemetatarsalian ankle. The forelimb to hindlimb length ratio is roughly 3:5, with much longer back legs than the front. Although the manus is missing, the overall similarity of Teleocrater suggests it would have had a relatively small hand. [2] [3] [4]

The osteoderms attributed to Yarasuchus are greatly sculptured with a ridge running anteroposteriorly along each one. [2] This is unusual in comparison to Teleocrater, which has been interpreted as lacking any form of similar dermal armour. However, these osteoderms are larger in proportion to the presacral vertebra than would be expected and bear a close similarity to osteoderms of an erythrosuchid also found in the same formation. Nesbitt and colleagues considered it probable that the osteoderms do not belong Yarasuchus and so it may have also lacked osteoderms like other aphanosaurs and avemetatarsalians. [3]

Discovery and naming

Yarasuchus is known from at least two individuals collected from a single 1 square metre (11 sq ft) assemblage in the Yerrapalli Formation, located near the Bhimaram village in the Adilabad district of India, in a layer of fine red mudstone. The material was found disarticulated, however it represents the majority of the skeleton, missing only the distal caudal vertebrae, radius, fibula, manus, and most of the pes and skull. The name is derived from 'Yara', meaning red in the local dialect, and the Greek suchos ("crocodile"), referring to the red mudstones the fossils were discovered in. The specific name refers to the Deccan region of India, where the Yerrapalli Formation and surrounding Pranhita-Godavari Basin are situated. [2] The fossils were also found in association with two specimens of the allokotosaur Pamelaria. [2] [4] [7] It was initially reported on in a 1993 thesis by Dasgupta, who considered it an indeterminate rauisuchid, [4] before being officially described and named as a new taxon by Sen in 2005. [2] All the material is held at the Geology Museum of the Indian Statistical Institute in Kolkata, India. [2] [3] [4]

In 2016, the material was re-examined by Nesbitt and colleagues in their description of Teleocrater, which revealed a number of previously unrecognised anatomical characteristics. This re-evaluation prompted the inclusion of Yarasuchus within the newly recognised avemetatarsalian clade Aphanosauria. In their examination, Nesbitt and colleagues were able to refer a number of previously undescribed calcanea collected at the site to the hypodigm of Yarasuchus based on their similarity to Teleocrater, and identified ischia that were originally reported as missing. They also removed a number of erroneously referred skull bones and osteoderms from the hypodigm. The relatively complete skeleton of Yarasuchus allowed Nesbitt and colleagues to confidently refer a number of isolated bones as all belonging to specimens of Teleocrater because of their close similarity to those of Yarasuchus, which provided a key reference point for understanding the anatomy of the previously enigmatic taxon. [3] [6]

Classification

Yarasuchus was originally described as a "prestosuchid", similar to Prestosuchus , Ticinosuchus, and Mandasuchus by Sen, however no phylogenetic analysis was performed and the referral was made based on general morphological similarities, despite the already debated validity of "Prestosuchidae". [2] In 2010, Brusatte and colleagues conclusively demonstrated that "Prestosuchidae" was a paraphyletic grade of paracrocodylomorphs, and that the supposed shared characteristics of the group were in fact found throughout Pseudosuchia. They also performed a detailed cladistic analysis of fossil Triassic archosaurs, which instead found Yarasuchus to be a basal member of Poposauroidea, although support for this position was weak. [8]

Restoration of Qianosuchus, a basal poposauroid formerly considered to be a close relative of Yarasuchus. Qianosuchus BW.jpg
Restoration of Qianosuchus , a basal poposauroid formerly considered to be a close relative of Yarasuchus.

The position of Yarasuchus in subsequent studies has been similarly unstable, [9] [10] [11] though it has nonetheless typically been regarded as a pseudosuchian. [12] [13] [14] A study by Ezcurra on archosauromorph phylogeny in 2016 found Yarasuchus in a position outside of Archosauria, clading together with Dongusuchus in a polytomy with Euparkeria and a clade made up of Proterochampsia and archosaurs. [15] The left cladogram depicts the results of Brusatte and colleagues in 2010, [8] while the right cladogram depicts that of Ezcurra in 2016: [15]

  Poposauroidea  

Further complicating the issue were suggestions that the hypodigm of Yarasuchus was a chimeric assemblage of material from both a "rauisuchian" archosaur and a prolacertiform archosauromorph, if not including material from yet other archosauromorphs. [16] [17] However, later examination of the material by Ezcurra found that none of it could be assigned to either a "rauisuchian" or prolacertiform, and that they all likely pertained to a single non-suchian archosauriform taxon. [15]

In 2017, Yarasuchus was included in an updated analysis of Triassic archosauromorphs by Nesbitt and colleagues in their official description of Teleocrater, utilising two modified datasets, those of Nesbitt (2011) [18] and Ezcurra (2016). [15] Both analyses recovered Yarasuchus in a newly recognised clade they named Aphanosauria, which included Yarasuchus in a polytomy with Teleocrater and Dongusuchus, as well as Spondylosoma. Indeed, the clade Aphanosauria was cladistically defined as "the most inclusive clade containing Teleocrater rhadinus and Yarasuchus deccanensis but not Passer domesticus or Crocodylus niloticus". Aphanosaurs were found to be the earliest diverging clade of Avemetatarsalia, sister taxon to the clade Ornithodira that includes the Pterosauria and Dinosauromorpha. [3] The results of their analyses are reproduced and simplified below, combining the general topology of the Ezcurra dataset with the Nesbitt dataset results for Avemetatarsalia.

Archosauriformes

Evolutionary significance

Life restoration of the closely related aphanosaur Teleocrater. Teleocrater v1.png
Life restoration of the closely related aphanosaur Teleocrater .

The recognition of a close relationship between Yarasuchus, Teleocrater and other aphanosaurs and their relation to other avemetatarsalians settled a number of the unusual anatomical features of Yarasuchus. Many of the previously unique features of Yarasuchus unite it with other aphanosaurs, including the elongated neck, high neural spines, three-headed cervical ribs and slender appendicular skeleton. Yarasuchus and the other aphanosaurs play a significant role in our understanding of early avemetatarsalian evolution, exemplified in the relatively completely known anatomy of Yarasuchus. The structure of the foot, particularly the bones of the ankle (such as the calcaneus), demonstrate that avemetatarsalians evolved from ancestors with 'crocodile-normal' ankles, unlike the simple hinge-like ankles characteristic of derived ornithodirans. The 'crocodile-normal' ankle was once thought to be unique to pseudosuchians, but its presence in aphanosaurs like Yarasuchus imply that the evolution of the avemetatarsalian ankle was a more complicated process than initially believed. [3] The anatomy of Yarasuchus also demonstrates that other typical avemetatarsalian features, such as slender limb girdles, had evolved prior to the eponymous 'advanced mesotarsal' ankles. [19]

Unusually, Yarasuchus and other aphanosaurs share a number of features convergently evolved with poposauroids. Aphanosaurs and poposauroids share only one unique trait (the presence of an accessory articulation facet just above the parapophysis of the cervicals for the three-headed cervical rib), however they have also convergently acquired a similar set of traits that are found throughout archosaurs. The previous phylogenetic position of Yarasuchus as a poposauroid by Brusatte and colleagues was likely due to this convergence. [6] The convergence between Yarasuchus and poposauroids could be attributed to the broader trend of poposauroids converging on coelurosaurian theropods, a derived clade of avemetatarsalians. [20] The similarity between poposauroids and aphanosaurs like Yarasuchus means it is difficult to determine the identity of isolated archosaur material that has features present in both groups, particularly as aphanosaurs are the earliest diverging avemetatarsalians while poposauroids are the oldest known pseudosuchians and so their stratigraphic ranges broadly overlap with each other. [6]

Palaeobiology

Yarasuchus was proposed to be facultatively bipedal by Dasgupta in 1993 on the basis of its gracile body, slender shoulder girdle and proportionately short forelimbs, among other features, and this suggestion was repeated by Sen in its official description in 2005. [2] [4] The closely related Teleocrater has since been interpreted to have been a quadruped, and as Yarasuchus has similar limb proportions, it likely was as well. [3] The lack of definitive jaw material leaves the diet of Yarasuchus ambiguous, however the teeth of Teleocrater imply aphanosaurs were carnivorous, as with other early avemetatarsalians. Furthermore, histological samples from Teleocrater show that its growth rates were more similar to those of other avemetatarsalians compared to pseudosuchians and stem-archosaurs, and so Yarasuchus may have also had a similarly higher growth rate. [3]

Palaeoecology

Restoration of the contemporary allokotosaur Pamelaria. Pamelaria dolichotrachela.jpg
Restoration of the contemporary allokotosaur Pamelaria .

Many other vertebrate remains have been found from the Yerrapalli Formation alongside those of Yarasuchus, and would have coexisted with it during the Middle Triassic. Remains of the allokotosaur Pamelaria in particular have been found in close proximity to those of Yarasuchus. [7] Other vertebrate remains include those of the lungfish Ceratodus , the actinopterygian fish Saurichthys , the temnospondyl Parotosuchus , the dicynodonts Rechnisaurus and Wadiasaurus , the rhynchosaur Mesodapedon , and a large undescribed erythrosuchid. [1] [4] [14]

Restoration of the contemporary dicynodont Wadiasaurus. Wadiasaurus1DB.jpg
Restoration of the contemporary dicynodont Wadiasaurus .

The anatomical similarity between Yarasuchus and Teleocrater is mirrored by the similarities in fauna and environment shared between the Yerrapalli Formation and the Manda Formation in Tanzania, and both are estimated to be Anisian in age. [1] [2] At the time, India was still a part of the supercontinent Gondwana in Pangaea, and was located directly adjacent to East Africa. This demonstrates that early avemetatarsalians like Yarasuchus were geographically widespread in the Middle Triassic, as with other archosauriforms, in contrast to previous suggestions that pseudosuchians were more diverse. The close similarity between Yarasuchus and the Russian Dongusuchus further supports this, indicating biogeographical affinities between India and Russia despite their widely separated palaeolatitudes. [3] [6] [15]

The sediments of the Yerrapalli Formation are interpreted as fluvial deposits, indicative of a broad, interchannel floodplain environment with seasonal ephemeral stream channels. The climate is thought to have been hot and dry with seasonal rainfall. This is consistent with the preservation state of the fossils, as the remains of Yarasuchus were found dismembered and disarticulated, suggesting the material was left exposed at the surface for a period before being buried by suspended fluvial sediments. [21] There are few plant fossils known from the Yerrapalli Formation, however this is not believed to be due to it being an arid environment, but rather due to the hot and dry conditions being unsuitable to the fossilisation of plant material. [4]

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"Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians than to birds and other dinosaurs. First named in the 1940s, Rauisuchia was a name exclusive to Triassic archosaurs which were generally large, carnivorous, and quadrupedal with a pillar-erect hip posture, though exceptions exist for all of these traits. Rauisuchians, as a traditional taxonomic group, were considered distinct from other Triassic archosaur groups such as early dinosaurs, phytosaurs, aetosaurs, and crocodylomorphs.

Spondylosoma is a genus of avemetatarsalian archosaur belonging to the clade Aphanosauria from the late Ladinian-age Middle Triassic Lower Santa Maria Formation in Paleorrota Geopark, Brazil.

<span class="mw-page-title-main">Pseudosuchia</span> Clade of reptiles

Pseudosuchia is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs". Despite Pseudosuchia meaning "false crocodiles", the name is a misnomer as true crocodilians are now defined as a subset of the group.

<span class="mw-page-title-main">Prestosuchidae</span> Extinct family of reptiles

Prestosuchidae is a polyphyletic grouping of carnivorous archosaurs that lived during the Triassic. They were large active terrestrial apex predators, ranging from around 2.5 to 7 metres in length. They succeeded the Erythrosuchidae as the largest archosaurs of their time. While resembling erythrosuchids in size and some features of the skull and skeleton, they were more advanced in their erect posture and crocodile-like ankle, indicating more efficient gait. "Prestosuchids" flourished throughout the whole of the middle, and the early part of the late Triassic, and fossils are so far known from Europe, India, Africa (Tanzania), Argentina, and Paleorrota in Brazil. However, for a long time experts disagree regarding the phylogenetic relationships of the group, what genera should be included, and whether indeed the "Prestosuchidae" constitute a distinct family.

<i>Teleocrater</i> Extinct genus of reptiles

Teleocrater is a genus of avemetatarsalian archosaur from the Middle Triassic Manda Formation of Tanzania. The name was coined by English paleontologist Alan Charig in his 1956 doctoral dissertation, but was only formally published in 2017 by Sterling Nesbitt and colleagues. The genus contains the type and only species T. rhadinus. Uncertainty over the affinities of Teleocrater have persisted since Charig's initial publication; they were not resolved until Nesbitt et al. performed a phylogenetic analysis. They found that Teleocrater is most closely related to the similarly enigmatic Yarasuchus, Dongusuchus, and Spondylosoma in a group that was named the Aphanosauria. Aphanosauria was found to be the sister group of the Ornithodira, the group containing dinosaurs and pterosaurs.

<i>Poposaurus</i> Extinct genus of Archosaur

Poposaurus is an extinct genus of pseudosuchian archosaur from the Late Triassic of the southwestern United States. It belongs to the clade Poposauroidea, an unusual group of Triassic pseudosuchians that includes sail-backed, beaked, and aquatic forms. Fossils have been found in Wyoming, Utah, Arizona, and Texas. Except for the skull, most parts of the skeleton are known. The type species, P. gracilis, was described and named by Maurice Goldsmith Mehl in 1915. A second species, P. langstoni, was originally the type species of the genus Lythrosuchus. Since it was first described, Poposaurus has been variously classified as a dinosaur, a phytosaur, and a "rauisuchian".

<i>Saurosuchus</i> Paracrocodylomorph reptile genus from Late Triassic period

Saurosuchus is an extinct genus of large loricatan pseudosuchian archosaurs that lived in South America during the Late Triassic period. It was a heavy, ground-dwelling, quadrupedal carnivore, likely being the apex predator in the Ischigualasto Formation.

<span class="mw-page-title-main">Ornithosuchidae</span> Extinct family of reptiles

Ornithosuchidae is an extinct family of pseudosuchian archosaurs from the Triassic period. Ornithosuchids were quadrupedal and facultatively bipedal, meaning that they had the ability to walk on two legs for short periods of time. They had distinctive, downturned snouts, unique, "crocodile-reversed" ankle bones, and several other features that distinguish them from other archosaurs. Ornithosuchids were geographically widespread during the Carnian and Norian stages of the Late Triassic with members known from Argentina, Brazil, and the United Kingdom. Four genera, comprising Ornithosuchus, Venaticosuchus, Dynamosuchus, and Riojasuchus are presently known. The family was first erected by German paleontologist Friedrich von Huene in 1908.

<i>Turfanosuchus</i> Extinct genus of reptiles

Turfanosuchus is a genus of archosauriform reptile, likely a gracilisuchid archosaur, which lived during the Middle Triassic (Anisian) of northwestern China. The type species, T. dabanensis, was described by C.C. Young in 1973, based on a partially complete but disarticulated fossil skeleton found in the Kelamayi Formation of the Turfan Basin.

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Dongusuchus is an extinct genus of archosaur. Fossils have been found from the Donguz Formation outcropping on the banks of the Donguz River in the Orenburg Oblast of Russia. They are associated with a fossil assemblage called the Eryosuchus Fauna, named after the capitosaurid Eryosuchus, the most common organism found from the assemblage. The locality dates back to the Anisian and early Ladinian stages of the Middle Triassic.

<i>Mandasuchus</i> Extinct genus of reptiles

Mandasuchus is an extinct genus of loricatan pseudosuchian from the Manda Formation of Tanzania, which dates back to the Anisian stage of the Middle Triassic. Although this genus was first mentioned by Alan Charig in 1956, a formal description was not published until 2018.

<span class="mw-page-title-main">Suchia</span> Clade of reptiles

Suchia is a clade of archosaurs containing the majority of pseudosuchians. It was defined as the least inclusive clade containing Aetosaurus ferratus, Rauisuchus tiradentes, Prestosuchus chiniquensis, and Crocodylus niloticus by Nesbitt (2011). Generally the only pseudosuchian group which is omitted from Suchia is the family Ornithosuchidae, although at least one analysis classifies ornithosuchids as close relatives of erpetosuchids and aetosaurs. Phytosaurs are also excluded from Suchia, although it is not certain whether they qualify as pseudosuchians in the first place.

<span class="mw-page-title-main">Poposauroidea</span> Extinct clade of reptiles

Poposauroidea is a clade of advanced pseudosuchians. It includes poposaurids, shuvosaurids, ctenosauriscids, and other unusual pseudosuchians such as Qianosuchus and Lotosaurus. It excludes most large predatory quadrupedal "rauisuchians" such as rauisuchids and "prestosuchids". Those reptiles are now allied with crocodylomorphs in a clade known as Loricata, which is the sister taxon to the poposauroids in the clade Paracrocodylomorpha. Although it was first formally defined in 2007, the name "Poposauroidea" has been used for many years. The group has been referred to as Poposauridae by some authors, although this name is often used more narrowly to refer to the family that includes Poposaurus and its close relatives.

<span class="mw-page-title-main">Paracrocodylomorpha</span> Clade of reptiles

Paracrocodylomorpha is a clade of pseudosuchian archosaurs. The clade includes the diverse and unusual group Poposauroidea as well as the generally carnivorous and quadrupedal members of Loricata, including modern crocodylians. Paracrocodylomorpha was named by paleontologist J. Michael Parrish in 1993, although the group is now considered to encompass more reptiles than his original definition intended. The most recent definition of Paracrocodylomorpha, as defined by Sterling Nesbitt in 2011, is "the least inclusive clade containing Poposaurus and Crocodylus niloticus. Most groups of paracrocodylomorphs became extinct at the end of the Triassic period, with the exception of the crocodylomorphs, from which crocodylians such as crocodiles and alligators evolved in the latter part of the Mesozoic.

<span class="mw-page-title-main">Erpetosuchidae</span> Extinct family of reptiles

Erpetosuchidae is an extinct family of pseudosuchian archosaurs. Erpetosuchidae was named by D. M. S. Watson in 1917 to include Erpetosuchus. It includes the type species Erpetosuchus granti from the Late Triassic of Scotland, Erpetosuchus sp. from the Late Triassic of eastern United States and Parringtonia gracilis from the middle Middle Triassic of Tanzania; the group might also include Dyoplax arenaceus from the Late Triassic of Germany, Archeopelta arborensis and Pagosvenator candelariensis from Brazil and Tarjadia ruthae from Argentina.

Nundasuchus is an extinct genus of crurotarsan, possibly a suchian archosaur related to Paracrocodylomorpha. Remains of this genus are known from the Middle Triassic Manda beds of southwestern Tanzania. It contains a single species, Nundasuchus songeaensis, known from a single partially complete skeleton, including vertebrae, limb elements, osteoderms, and skull fragments.

Aphanosauria is an extinct group of reptiles distantly related to dinosaurs. They are at the base of a group known as Avemetatarsalia, one of two main branches of archosaurs. The other main branch, Pseudosuchia, includes modern crocodilians. Aphanosaurs possessed features from both groups, indicating that they are the oldest and most primitive known clade of avemetatarsalians, at least in terms of their position on the archosaur family tree. Other avemetatarsalians include the flying pterosaurs, small bipedal lagerpetids, herbivorous silesaurids, and the incredibly diverse dinosaurs, which survive to the present day in the form of birds. Aphanosauria is formally defined as the most inclusive clade containing Teleocrater rhadinus and Yarasuchus deccanensis but not Passer domesticus or Crocodylus niloticus. This group was first recognized during the description of Teleocrater. Although only known by a few genera, Aphanosaurs had a widespread distribution across Pangaea in the Middle Triassic. They were fairly slow quadrupedal long-necked carnivores, a biology more similar to basal archosaurs than to advanced avemetatarsalians such as pterosaurs, lagerpetids, and early dinosaurs. In addition, they seemingly possess 'crocodile-normal' ankles, showing that 'advanced mesotarsal' ankles were not basal to the whole clade of Avemetatarsalia. Nevertheless, they possessed elevated growth rates compared to their contemporaries, indicating that they grew quickly, more like birds than other modern reptiles. Despite superficially resembling lizards, the closest modern relatives of aphanosaurs are birds.

Aenigmaspina is an extinct genus of enigmatic pseudosuchian (=crurotarsan) archosaur from the Late Triassic of the United Kingdom. Its fossils are known from the Pant-y-ffynnon Quarry in South Wales, of which its type and only known species is named after, A. pantyffynnonensis. Aenigmaspina is characterised by the unusual spines on its vertebrae, which are broad and flat on top with a unique 'Y' shape. Although parts of its skeleton is relatively well known, the affinities of Aenigmaspina to other pseudosuchians are unclear, although it is possibly related to families Ornithosuchidae, Erpetosuchidae or Gracilisuchidae.

Mambachiton is an extinct genus of basal avemetatarsalian from the Middle/Upper Triassic Makay Formation of Madagascar. The genus contains a single species, M. fiandohana, known from a partial skeleton with articulated osteoderms.

References

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  3. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 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. S2CID   9095072.
  4. 1 2 3 4 5 6 7 8 9 10 11 Kasturi, Dasgupta (1993). "New reptiles diapsida archosauromorpha from the triassic yerrapalli formation Deccan India their importance in geology and palaeontology". University. hdl:10603/159402?mode=simple.
  5. ↑ Jalil, Nour-Eddine; Peyer, Karin (2007). "A new rauisuchian (Archosauria, Suchia) from the Upper Triassic of the Argana Basin, Morocco". Palaeontology . 50 (2): 417–430. Bibcode:2007Palgy..50..417J. doi: 10.1111/j.1475-4983.2007.00640.x .
  6. 1 2 3 4 5 6 Nesbitt, S.J.; Butler, R.J.; Ezcurra, M.D.; Charig, A.J.; Barrett, P.M. (2018). "The anatomy of Teleocrater rhadinus, an early avemetatarsalian from the lower portion of the Lifua Member of the Manda Beds (Middle Triassic)" (PDF). Journal of Vertebrate Paleontology. 37 (Supplement to No. 6): 142–177. doi:10.1080/02724634.2017.1396539. S2CID   90421480.
  7. 1 2 Sen, K. (2003). Pamelaria dolichotrachela, a new prolacertid reptile from the Middle Triassic of India. Journal of Asian Earth Sciences21: 663–681.
  8. 1 2 Brusatte, S.L.; Benton, M.J.; Desojo, J.B.; Langer, M.C. (2010). "The higher-level phylogeny of Archosauria (Tetrapoda: Diapsida)" (PDF). Journal of Systematic Palaeontology. 8 (1): 3–47. Bibcode:2010JSPal...8....3B. doi:10.1080/14772010903537732. hdl:11336/69099. S2CID   59148006.
  9. ↑ Butler, R.J.; Brusatte, S.L.; Reich, M.; Nesbitt, S.J.; Schoch, R.R.; Hornung, J.J. (2011). "The sail-backed reptile Ctenosauriscus from the latest Early Triassic of Germany and the timing and biogeography of the early archosaur radiation". PLOS ONE. 6 (10): e25693. Bibcode:2011PLoSO...625693B. doi: 10.1371/journal.pone.0025693 . PMC   3194824 . PMID   22022431.
  10. ↑ Marco Aurélio G. França; Jorge Ferigolo; Max C. Langer (2011). "Associated skeletons of a new middle Triassic "Rauisuchia" from Brazil". Naturwissenschaften. 98 (5): 389–395. Bibcode:2011NW.....98..389F. doi:10.1007/s00114-011-0782-3. PMID   21445632. S2CID   4811617.
  11. ↑ Nesbitt, Sterling J.; Sidor, Christian A.; Angielczyk, Kenneth D.; Smith, Roger M. H.; Tsuji, Linda A. (November 2014). "A new archosaur from the Manda beds (Anisian, Middle Triassic) of southern Tanzania and its implications for character state optimizations at Archosauria and Pseudosuchia". Journal of Vertebrate Paleontology. 34 (6): 1357–1382. Bibcode:2014JVPal..34.1357N. doi:10.1080/02724634.2014.859622. S2CID   129558756.
  12. ↑ Desojo, J.B.; Arcucci, A.B. (2009). "New material of Luperosuchus fractus (Archosauria: Crurotarsi) from the Middle Triassic of Argentina: the earliest known South American "rauisuchian"". Journal of Vertebrate Paleontology. 29 (4): 1311–1315. Bibcode:2009JVPal..29.1311D. doi:10.1671/039.029.0422. S2CID   132648252.
  13. ↑ Lautenschlager, S.; Rauhut, O.W.M. (2015). "Osteology of Rauisuchus tiradentes from the Late Triassic (Carnian) Santa Maria Formation of Brazil, and its implications for rauisuchid anatomy and phylogeny". Zoological Journal of the Linnean Society . 173 (1): 55–91. doi: 10.1111/zoj.12196 .
  14. 1 2 Chatterjee, Sankar; Scotese, Christopher R.; Bajpai, Sunil (2017). Indian Plate and Its Epic Voyage from Gondwana to Asia: Its Tectonic, Paleoclimatic, and Paleobiogeographic Evolution. Vol. 529 (Illustrated ed.). Geological Society of America. pp. 28–29. ISBN   978-0813725291.
  15. 1 2 3 4 5 Ezcurra, M.D. (2016). "The phylogenetic relationships of basal archosauromorphs, with an emphasis on the systematics of proterosuchian archosauriforms". PeerJ . 4: e1778. doi: 10.7717/peerj.1778 . ISSN   2167-8359. PMC   4860341 . PMID   27162705.
  16. ↑ Lautenschlage, S.; Desojo, J.B. (2011). "Reassessment of the Middle Triassic rauisuchian archosaurs Ticinosuchus ferox and Stagonosuchus nyassicus". Paläontologische Zeitschrift . 85 (4): 357–381. doi:10.1007/s12542-011-0105-1. hdl: 11336/68929 . ISSN   1867-6812. S2CID   86671911.
  17. ↑ Nesbitt, S.J.; Brusatte, S.L.; Desojo, J.B.; Liparini, A.; De França, M.A.G.; Weinbaum, J.C.; Gower, D.J. (2013). "Rauisuchia". Geological Society, London, Special Publications . 379 (1): 241–274. Bibcode:2013GSLSP.379..241N. doi:10.1144/SP379.1. S2CID   219193351.
  18. ↑ Nesbitt, S.J. (2011). "The early evolution of archosaurs: relationships and the origin of major clades". Bulletin of the American Museum of Natural History. 352: 1–292. doi: 10.1206/352.1 . hdl:2246/6112. S2CID   83493714.
  19. ↑ Cau, Andrea (2018). "The assembly of the avian body plan: a 160-million-year long process" (PDF). Bollettino della Società Paleontologica Italiana. 57 (1): 1–25. doi:10.4435/BSPI.2018.01.
  20. ↑ Nesbitt, Sterling J. (2007). "The anatomy of Effigia okeeffeae (Archosauria, Suchia), theropod-like convergence, and the distribution of related taxa". Bulletin of the American Museum of Natural History . 302 (302): 1–84. doi:10.1206/0003-0090(2007)302[1:TAOEOA]2.0.CO;2. hdl:2246/5840. S2CID   55677195.
  21. ↑ Brandyopadhyay, S.; Roy Chowdhury, T.K.; Sengupta, D.P. (2002). "Taphonomy of some Gondwana vertebrate assemblages of India". Sedimentary Geology . 147 (1–2): 219–245. Bibcode:2002SedG..147..219B. doi:10.1016/S0037-0738(01)00198-1.
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