Dyoplax

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Dyoplax
Temporal range: 228  Ma
Dyoplax holotype.jpg
Original lithographic illustration of the holotype of Dyoplax arenaceus, from Fraas, 1867
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Suchia
Family: Erpetosuchidae
Genus: Dyoplax
Fraas, 1867
Type species
Dyoplax arenaceus
Fraas, 1867

Dyoplax is an extinct genus of pseudosuchian archosaur, possibly an erpetosuchid. Fossils have been found from the type locality within the upper Schilfsandstein Formation in Stuttgart, Germany. The holotype specimen was a natural cast of a nearly complete skeleton that lacked only parts of the tail and limb bones. [1]

Classification

Oscar Fraas, the original describer of Dyoplax, described the specimen as having "the head of a lizard and the armor of a gavial". [2] When the taxon Pseudosuchia was first proposed in 1890, Dyoplax was considered one of the three genera within the clade, and was included within the family "Aetosauridae". [3] Several other papers published in later years have also placed the genus within Pseudosuchia. [4] [5] [6] [7] In 1956 the genus was referred to Notochampsidae, now known as Protosuchidae. [8] It was suggested to be a possible erpetosuchid in 1966, [9] [10] but was later classified as one of the earliest protosuchids in 1994. [11]

In that same year a paper was published that identified several synamomorphies characteristic of the clade Aetosauria. [12] This confirmed that Dyoplax was not within the order Aetosauria as had been previously speculated because it lacked four out of five of the synapomorphies associated with Aetosauria.

A paper published in 1998 by Spencer et al. considered Dyoplax to be within Sphenosuchia, a grade of basal crocodylomorphs. [13] The authors claimed that all synapomorphies present within Crocodylomorpha, as defined in 1992 by Sereno & Wild, were present in Dyoplax. [14] They further concluded that the genus had most of the synapomorphies common to Sphenosuchia, lacking only the forked posterior process of the squamosal. On this basis, the authors concluded that there was enough evidence to place Dyoplax within Sphenosuchia. The age of the specimen within the strata would make Dyoplax the oldest sphenosuchian known at the time, predating other genera from the late Carnian that were once thought to be the oldest members of Sphenosuchia such as Hesperosuchus and Parrishia . [15] However, Maisch, Matzke and Rathgeber (2013) questioned the placement of Dyoplax within Crocodylomorpha, and argued that it shared important cranial and postcranial features with Erpetosuchus ; the authors tentatively reassigned Dyoplax to Erpetosuchidae. [1]

Paleoecology

The Shilfsandstein Formation was deposited during the early Carnian stage of the Late Triassic (~ 228 million years ago) in a lagoonal paleoenvironment. Numerous bivalves, chondrichthyean fish such as Palaeobates , trematosaurian temnospondyls such as Metoposaurus , [16] [17] a phytosaur, and plants such as Neocalamites and Equisetites were also present in the paleoenvironment that existed at the time.

Related Research Articles

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

Saltoposuchus is an extinct genus of small, long-tailed crocodylomorph reptile (Sphenosuchia), from the Norian of Europe. The name translated means "leaping foot crocodile". It has been proposed that Terrestrisuchus gracilis and Saltoposuchus connectens represent different ontogenetic stages of the same genus. Saltoposuchus was commonly referred to in popular literature as the ancestor to dinosaurs; however, recent scientific research shows that this is not the case.

<i>Procompsognathus</i> Extinct genus of dinosaurs

Procompsognathus is an extinct genus of coelophysid theropod dinosaur that lived approximately 210 million years ago during the later part of the Triassic Period, in what is now Germany. Procompsognathus was a small-sized, lightly built, ground-dwelling, bipedal carnivore, that could grow up to 1 m (3.3 ft) long.

<span class="mw-page-title-main">Aetosaur</span> Extinct order of heavily armoured reptiles

Aetosaurs are heavily armored reptiles belonging to the extinct order Aetosauria. They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs more closely related to crocodilians than to birds and other dinosaurs. All known aetosaurs are restricted to the Late Triassic, and in some strata from this time they are among the most abundant fossil vertebrates. They have small heads, upturned snouts, erect limbs, and a body ornamented with four rows of plate-like osteoderms. Aetosaur fossil remains are known from Europe, North and South America, parts of Africa, and India. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic tetrapod index fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site in which they are found.

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

Trialestes is an extinct genus of Late Triassic (Carnian) crocodylomorphs that lived in South America. It has been classified as a dinosaur in the past due it being adapted as a terrestrial, running carnivore. It is classified in Sphenosuchia, which were early relatives of crocodylians. Irmis, Nesbitt and Sues (2013) noted that some of the material referred to this taxon is actually dinosaurian; however, according to the authors, the holotype specimen PVL 2561, found in the Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina, "comprises a single individual that preserves unambiguous crocodylomorph synapomorphies", indicating it is indeed a crocodylomorph, and one of the referred specimens, PVL 3889, does share one or more autapomorphies with the holotype, indicating it represents the same taxon. The type species, T. romeri, was named in 1963.

<i>Gracilisuchus</i> Genus of fossil reptiles

Gracilisuchus is an extinct genus of tiny pseudosuchian from the Late Triassic of Argentina. It contains a single species, G. stipanicicorum, which is placed in the clade Suchia, close to the ancestry of crocodylomorphs. Both the genus and the species were first described by Alfred Romer in 1972.

<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.

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

Paleorhinus is an extinct genus of widespread basal phytosaur known from the Late Triassic. The genus was named in 1904 based on the type species Paleorhinus bransoni, which is known from Wyoming and Texas in the United States. Another valid species, Paleorhinus angustifrons from Bavaria, Germany, is also commonly referred to the genus. Paleorhinus had a length of about 2.5 meters.

<span class="mw-page-title-main">Sphenosuchia</span> Suborder of reptiles

Sphenosuchia is a suborder of basal crocodylomorphs that first appeared in the Triassic and occurred into the Middle Jurassic. Most were small, gracile animals with an erect limb posture. They are now thought to be ancestral to crocodyliforms, a group which includes all living crocodilians.

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

Aetosauroides is an extinct genus of aetosaur from the Late Triassic of South America. It is one of four aetosaurs known from South America, the others being Neoaetosauroides, Chilenosuchus and Aetobarbakinoides. Three species have been named: the type species A. scagliai, A. subsulcatus and A. inhamandensis. Fossils have been found in the Cancha de Bochas Member of the Ischigualasto Formation in the Ischigualasto-Villa Unión Basin in northwestern Argentina and the Santa Maria Formation in the Paraná Basin in southeastern Brazil. The strata date to the late Carnian and early Norian stages, making Aetosauroides one of the oldest aetosaurs.

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

Erpetosuchus is an extinct genus of pseudosuchian from the Late Triassic. The type species of Erpetosuchus is E. granti. It was first described by E. T. Newton in 1894 for remains found in northeastern Scotland, including four specimens from the latest Carnian Lossiemouth Sandstone Formation. Additional remains of Erpetosuchus have been found in the New Haven Formation of Connecticut in the eastern United States, although they were not attributed to the species E. granti. The relationship of Erpetosuchus to other archosaurs is uncertain. In 2000 and 2002, it was considered a close relative of the group Crocodylomorpha, which includes living crocodylians and many extinct relatives. However, this relationship was questioned in a 2012 analysis that found the phylogenetic placement of Erpetosuchus to be very uncertain.

<i>Litargosuchus</i> Extinct genus of reptiles from the early Jurassic of South Africa

Litargosuchus is a sphenosuchian crocodylomorph, a basal member of the crocodylomorph clade from the Early Jurassic of South Africa. Its genus name Litargosuchus is derived from Greek meaning "fast running crocodile" and its species name leptorhynchus refers to its gracile snout. Litargosuchus, along with all of South Africa's crocodylomorph taxa, are confined to the upper Elliot Formation (UEF) in South Africa.

Lucasuchus is an extinct genus of aetosaur. Fossils have been found from the Bull Canyon Formation of the Dockum Group outcropping in the Revuelto Creek locality in Quay County, New Mexico. All specimens date back to the Norian stage of the Late Triassic. The genus was named in 1995 after the American paleontologist Spencer G. Lucas.

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

Pseudhesperosuchus is a genus of sphenosuchian, a type of basal crocodylomorph, the clade that comprises the crocodilians and their closest kin. It is known from a partial skeleton and skull found in rocks of the Late Triassic (Norian-age) Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.

Notochampsa is an extinct genus of protosuchian crocodyliform. Fossils have been found from the lower Clarens Formation of the Karoo Supergroup in South Africa, dating back to the Pliensbachian stage of the Early Jurassic. Notochampsa comes from a period of relative fossil scarcity, and is the youngest known occurrence of a crocodylomorph from the Karoo Basin of South Africa.

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

Parringtonia is an extinct genus of Triassic archosaur within the family Erpetosuchidae, known from the type species Parringtonia gracilis. It is known from a single specimen, NHMUK R8646, found from the Anisian-age Manda Formation of Tanzania. This specimen, like most archosaur material from the Manda Formation, is fragmentary, including only a maxilla and a few postcranial bones. They show similarities with those of another archosaur called Erpetosuchus, known from the Middle Triassic of Scotland and the eastern United States. The phylogenetic placement of Parringtonia and Erpetosuchus are uncertain; some studies placed them close to the group Crocodylomorpha, which includes all modern crocodylians and many extinct forms that diversified after the Triassic, but this relationship has more recently been questioned.

Procerosuchus is an extinct genus of loricatan archosaur. Fossils have been collected from the Late Triassic Santa Maria Formation in Geopark of Paleorrota, Rio Grande do Sul, Brazil, which is Carnian in age. The genus was first described by the German paleontologist Friedrich von Huene in 1942.

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

Tarjadia is an extinct genus of erpetosuchid pseudosuchian, distantly related to modern crocodilians. It is known from a single species, T. ruthae, first described in 1998 from the Middle Triassic Chañares Formation in Argentina. Partial remains have been found from deposits that are Anisian-Ladinian in age. Long known mostly from osteoderms, vertebrae, and fragments of the skull, specimens described in 2017 provided much more anatomical details and showed that it was a fairly large predator. Tarjadia predates known species of aetosaurs and phytosaurs, two Late Triassic groups of crurotarsans with heavy plating, making it one of the first heavily armored archosaurs. Prior to 2017, most studies placed it outside Archosauria as a member of Doswelliidae, a family of heavily armored and crocodile-like archosauriforms. The 2017 specimens instead show that it belonged to the Erpetosuchidae.

<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">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.

References

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