Litargosuchus Temporal range: Early Jurassic | |
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Life restoration of Litargosuchus leptorhynchus | |
Scientific classification ![]() | |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Reptilia |
Clade: | Pseudosuchia |
Superorder: | Crocodylomorpha |
Genus: | † Litargosuchus Clark and Sues 2002 |
Type species | |
†L. leptorhynchus Clark and Sues 2002 |
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. [1] [2] [3]
In 1988 James Kitching found the holotype fossil of Litargosuchus in a field expedition in Eagles Crag, a farm near Barkly East in the Eastern Cape. [4] The material recovered consisted of a near-complete skull with its mandible and several bones belonging to the postcranial skeleton. At the time, Kitching was the director of the Evolutionary Studies Institute (previously the Bernard Price Institute) of the University of the Witwatersrand in Johannesburg. Kitching brought the holotype fossil back to the institute where he described it with fellow researcher, Christopher Gow. [5] Together Kitching and Gow unfortunately misidentified this new species of sphenosuchian crocodylomorph and assigned the fossils to an existing crocodylomorph species, Pedeticosaurus leviseuri . Over a decade later in 2002, two researchers visiting from abroad, Jim Clark and Hans-Dieter Sues, re-described the fossils. After their analysis, Clark and Sues discovered that the fossils belonged to a new species of sphenosuchian crocodylomorph and coined the current name for the species. [6] The Litargosuchus fossil is monotypic and is the only known fossil of this species that has been found to date.
Unfortunately, the skull material of the Litargosuchus holotype was lost and no new fossils have yet been yielded from the Elliot Formation. However, new Litargosuchus fossils may be found in the future. A dedicated research lab based at the Evolutionary Studies Institute has led several field expeditions to localities where Elliot Formation rocks are exposed with the hope of finding more fossil material. Jonah Choiniere, an old PhD student of Clark, leads this research lab. The remains of the holotype currently remain stored at the Evolutionary Studies Institute.
Litargosuchus was a small, gracile non-crocodyliform spheosuchid crocodylomorph restricted to the Sinemurian of the lower Jurassic. Unlike modern crocodiles, Litargosuchus was a cursorial, terrestrial predator. [7] [8] It had unusually elongated limbs with its hind limbs slightly longer than its front. All sphenosuchian crocodylomorphs were lightly built, but Litargosuchus was especially so. It is thought that Litargosuchus pursued its prey much like a wolf; however, Litargosuchus were likely solitary. [9] A cursorial body type is a key character trait of sphenosuchid crocodylomorphs. [10] [11]
The holotype specimen, BP/1/523 is the only documented Litargosuchus specimen recovered to date.
Litargosuchus is currently positioned within Sphenosuchidae, a basal clade of non-crocodyloform crocodylomorphs. However, phylogenetic relationships within the Sphenosuchia are poorly understood so its status within this clade is uncertain. In addition, only one specimen of Litargosuchus is known to science, which means that there is no other comparative fossil data with members of its own species. However, it is accepted as a member of the greater crown archosaur clade.
"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.
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 show that this is not the case.
Hallopus was a prehistoric reptile, named in 1877 as a species of Nanosaurus and classified by O. C. Marsh in 1881 from the Late Jurassic Morrison Formation. Today though the animal is thought to be a pseudosuchian more closely related to crocodilians. It was redescribed as a sphenosuchian crocodylomorph in 1970, now thought to be a paraphyletic group. It was a quite small animal, reaching a length of 1 m (3.3 ft) with long and slender limbs. Macelognathus, a similarilly slender-proportioned crocodylomorph to Hallopus, may be synonymous with it.
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". Prior to 2011, the clade Pseudosuchia was often called Crurotarsi in reference to the crurotarsal ankle found in almost all members of the group, which traditionally included phytosaurs, ornithosuchids, and suchians. However, a major 2011 study of Triassic archosaur relations proposed that phytosaurs were not closely related to other traditional "crurotarsans", at least compared to "bird-line archosaurs" (Avemetatarsalians) such as pterosaurs and dinosaurs. As a result, the possession of a crurotarsal ankle was considered a plesiomorphic ("primitive") feature retained by pseudosuchians. Crurotarsi now refers to a broader group of reptiles including Pseudosuchia, Phytosauria, and Avemetatarsalia. Despite Pseudosuchia meaning "false crocodiles", the name is a misnomer as true crocodilians are a subset of the group.
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.
Terrestrisuchus is an extinct genus of very small early crocodylomorph that was about 76 centimetres (30 in) long. Fossils have been found in Wales and Southern England and date from near the very end of the Late Triassic during the Rhaetian, and it is known by type and only known species T. gracilis. Terrestrisuchus was a long-legged, active predator that lived entirely on land, unlike modern crocodilians. It inhabited a chain of tropical, low-lying islands that made up southern Britain, along with similarly small-sized dinosaurs and abundant rhynchocephalians. Numerous fossils of Terrestrisuchus are known from fissures in limestone karst which made up the islands it lived on, which formed caverns and sinkholes that preserved the remains of Terrestrisuchus and other island-living reptiles.
Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction.
Dromicosuchus is an extinct genus of sphenosuchian, a type of basal crocodylomorph, the clade that comprises the crocodilians and their closest kin. It was found in Upper Triassic rocks of North Carolina, United States, and is known from a nearly complete skull and partial skeleton. This specimen is unusual in that it was found beneath the skeleton of a larger rauisuchian and has apparent bite damage, suggesting that it was attacked by the larger carnivore before both died and were buried together.
Pedeticosaurus is an extinct genus of crocodylomorph from the Clarens Formation of South Africa. The type species Pedeticosaurus leviseuri was named by Egbert Cornelis Nicolaas van Hoepen in 1915 on the basis of a mold of a mostly complete skeleton found in a quarry near Rosendal, Free State. The mold preserves most of the right half of the skeleton including the skull, ribs, dorsal vertebrae, forelimbs and hindlimbs, but not the tail. It is currently housed in the National Museum in Bloemfontein and cataloged as NMQR606.
Yarasuchus is an extinct genus of avemetatarsalian archosaur that lived during the Anisian stage of the Middle Triassic of India. 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. 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.
Dibothrosuchus is a genus of sphenosuchian, a type of basal crocodylomorph, the clade that comprises the crocodilians and their closest kin. It is known from several partial skeletons and skulls. These fossils were found in Lower Jurassic rocks of Yunnan, China. Dibothrosuchus was a small terrestrial crocodylomorph that probably had a keen sense of hearing, and thus was probably a vocal animal like modern crocodilians.
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Sterling Nesbitt is an American paleontologist best known for his work on the origin and early evolutionary patterns of archosaurs. He is currently an associate professor at Virginia Tech in the Department of Geosciences.
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