Hesperosuchus

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Hesperosuchus
Temporal range: Late Triassic, 220  Ma
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Hesperosuchus BW.jpg
Hesperosuchus agilis
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Crocodylomorpha
Genus: Hesperosuchus
Colbert, 1952
Species:
H. agilis
Binomial name
Hesperosuchus agilis
Colbert, 1952

Hesperosuchus is an extinct genus of crocodylomorph reptile that contains a single species, Hesperosuchus agilis. Remains of this pseudosuchian have been found in Late Triassic (Carnian) strata from Arizona and New Mexico. [1] Because of similarities in skull and neck anatomy and the presence of hollow bones Hesperosuchus was formerly thought to be an ancestor of later carnosaurian dinosaurs, but based on more recent findings and research it is now known to be more closely related to crocodilians rather than dinosaurs. [2] [3]

Contents

Description

Size compared to a human Hesperosuchus.jpg
Size compared to a human

Stance and limbs

At only about 4 to 5 feet (1.2 to 1.5 m) in length, Hesperosuchus is a relatively small and lightly built pseudosuchian. It is very closely comparable to the different genera, Ornithosuchus woodwardi and Saltoposuchus longipes , [4] [5] which are both pseudosuchians as well. The hind limbs of Hesperosuchus are large and strong, while the forelimbs were smaller and much more slender. This observation lead to the hypothesis that Hesperosuchus was a bipedal animal. Comparing the hind limbs of Saltoposuchus with those of Hesperosuchus, they are evenly as large and strong. The length of the extended hind limb in both genera are approximately equal to the length of the presacral vertebrae. Saltoposuchus was described by van Huene, and portrayed as a facultative quadruped. It is believed that Hesperosuchus also practiced both bipedialism and quadrupedalism. Though it is believed to be more often on two feet as the long slender hands looked as if it was adapted for grasping, which may have been useful for food gathering, digging or defense. Five digits were found on both the hind limbs as well as the forelimbs. In order to counterbalance the weight of its body, Hesperosuchus is inferred to have had a relatively long tail. Since the caudal vertebrae aren't completely restored, it is inferred based on similar archosaurians, that the tail contained somewhere around 45 caudal vertebrae. The strong hind limbs and overall light weight made Hesperosuchus very quick and able to move rapidly. This advantage of speed allowed for it to catch small prey and escape from larger predators. [1]

Skull

The skull of Hesperosuchus was only partially preserved and is missing many segments. The mandible and the skull of the specimen found was very poorly preserved, but there is just enough bone present to provide for an indication of what the basic structure of the jaw and skull may have looked like. It was found that the skull very closely resembled that of Ornithosuchus. In the fronto-parietal regions of the skull, along with a flat cranial roof, marked depressions were found in the frontal and post orbital bones, in front of and lateral to the supratemporal fenestrae. [1] Fragments of the left premaxilla and maxilla were found to have sockets for nine teeth, with four being in the premaxilla. The first premaxillary teeth start out small in size and progressively get larger with the fourth tooth being clearly enlarged. This was compared to the skull of Ornithosuchus, which is defined with characteristics of two enlarged teeth in this similar area; the first two maxillary teeth. [5] The teeth of Hesperosuchus are serrated in both the posterior and anterior edges which supports the fact that Hesperosuchus was a meat eating animal. With the two fragments of the jaws found, only 14 teeth in total were reported with five in the posterior fragment and nine in the anterior one. The basioccipital region is defined as typically archosaurian, [2] with a rounded condyle, a rather elongated surface above it for the medulla oblongata, and an extended ventral plate. [1] These basioccipital characteristics are seen in extinct archosaurians [2] such as primitive theropod dinosaurs as well as seen in crocodylians. [3] It can be seen that the skull would have been relatively large which was compared to carnosaurian dinosaurs, which too had fairly large skulls. It can be said that both these groups were active and carnivorous as large skulls allow for wide gaping jaws to catch and attack prey. Such large skulls need to be light as a large antorbital opening is present and clearly shown in Hesperosuchus. [1]

Soft tissue reconstruction

Ziphodont dentition and theropod-like pattern of linearly arranged jaw foramina of Hesperosuchus suggest a possible existence of lips that protected its teeth from the outside. [6]

Discovery

Hesperosuchus was discovered in upper Triassic rocks of Northern Arizona by Llewellyn I. Price, William B. Hayden, and Barnum Brown in the fall of 1929 and the summer of 1930. The specimen was then taken to a museum for Otto Falkenbach to carefully and precisely put together. [1] Many different illustrations of the bones were done by Sydney Prentice from the Carnegie Museum of Pittsburgh. In addition, models and figures were also made by John LeGrand Lois Darling from the Museum Illustrators Corps. [1]

The exact location where the specimen was found is an area 6 miles (9.7 km) southeast of Cameron, Arizona, close to the old Tanner Crossing of the Little Colorado River. [7] This area, in particular, is a very prevalent for finding many Triassic vertebrates. [8] [9] This area is about 160 miles (260 km) on top of the Moen kopi formation, in the portion of the Chinle formation [10] where the Little Colorado River flows through a canyon. [8]

Along with Hesperosuchus, many other specimens were found in the same general area. There were many ganoid scales believed to have belonged to Triassic freshwater holostean fish, several phytosaur teeth, and many small stereospondyl vertebrae. In addition, a large number of small teeth were found, some which definitely belonged to Hesperosuchus, and some belonging to amphibian related animals. It is hypothesized that these other teeth may have belonged to animals that Hesperosuchus may have preyed upon. [1]

Hesperosuchus was a contemporary of Coelophysis , a primitive predatory theropod dinosaur. Coelophysis was long thought to have been a cannibal, based on the presence of putative juvenile Coelophysis bones in the gut regions of a few adults. However, in some of these cases, it was later found that the "juvenile Coelophysis" bones were actually those of a Hesperosuchus (or something very similar) instead. [11]

Paleoecology

Restoration Crocodylomorph.jpg
Restoration

Hesperosuchus was a terrestrial animal, where its speed and ability to run fast is the most advantageous as a fitness trait. Northern Arizona's landscape during the Triassic period was surrounded by numerous bodies of water like lakes and streams. [10] [7] This supports that Hesperosuchus likely lived close to water although being a full on land-dwelling animal. The ganoid scales found in the general area where Hesperosuchus was found belong to freshwater fish of the Triassic period, belonging to the genus Semionolus or Lepidolus , which lived in shallow lakes and streams. The phytosaur teeth and small stereospondyl vertebrae found near Hesperosuchus support the presence of lakes or streams crossing a flood plain. Also the many small teeth found, which some, belong to amphibians of the Triassic period supports the occupying of near water habitats. [1]

See also

Related Research Articles

<i>Coelophysis</i> Genus of theropod dinosaurs from the late Triassic

Coelophysis is a genus of coelophysid theropod dinosaur that lived approximately 215 to 208.5 million years ago during the Late Triassic period from the middle to late Norian age in what is now the southwestern United States. Megapnosaurus was once considered to be a species within this genus, but this interpretation has been challenged since 2017 and the genus Megapnosaurus is now considered valid.

<span class="mw-page-title-main">Rauisuchia</span> Informal group of Triassic archosaurs with pillar-erect posture

"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.

<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>Postosuchus</i> Genus of reptiles

Postosuchus, meaning "Crocodile from Post", is an extinct genus of rauisuchid reptiles comprising two species, P. kirkpatricki and P. alisonae, that lived in what is now North America during the Late Triassic. Postosuchus is a member of the clade Pseudosuchia, the lineage of archosaurs that includes modern crocodilians. Its name refers to Post Quarry, a place in Texas where many fossils of the type species, P. kirkpatricki, were found. It was one of the apex predators of its area during the Triassic, larger than the small dinosaur predators of its time. It was a hunter which probably preyed on large bulky herbivores like dicynodonts and many other creatures smaller than itself.

Podokesaurus is a genus of coelophysoid dinosaur that lived in what is now the eastern United States during the Early Jurassic Period. The first fossil was discovered by the geologist Mignon Talbot near Mount Holyoke, Massachusetts, in 1910. The specimen was fragmentary, preserving much of the body, limbs, and tail. In 1911, Talbot described and named the new genus and species Podokesaurus holyokensis based on it. The full name can be translated as "swift-footed lizard of Holyoke". This discovery made Talbot the first woman to find and describe a non-bird dinosaur. The holotype fossil was recognized as significant and was studied by other researchers, but was lost when the building it was kept in burned down in 1917; no unequivocal Podokesaurus specimens have since been discovered. It was made state dinosaur of Massachusetts in 2022.

<i>Ornithosuchus</i> Genus of reptiles

Ornithosuchus is an extinct genus of pseudosuchians from the Late Triassic (Carnian) Lossiemouth Sandstone of Scotland. It was originally thought to be the ancestor to the carnosaurian dinosaurs, but it is now known to be more closely related to crocodilians than to dinosaurs.

Spinosuchus is an extinct genus of trilophosaurid allokotosaur from the Late Triassic of Texas, southern United States. It has been assigned to a variety of groups over its history, from coelophysid dinosaur to pseudosuchian to uncertain theropod dinosaur and to Proterosuchidae. This uncertainty is not unusual, given that it was only known from a poorly preserved, wall-mounted, partial vertebral column of an animal that lived in a time of diverse, poorly known reptile groups. However, newly collected material and recent phylogenetic studies of early archosauromorphs suggest that it represents an advanced trilophosaurid very closely related to Trilophosaurus.

<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.

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

Riojasuchus is an extinct genus of ornithosuchid archosaur from the Late Triassic (Norian) of Argentina. Ornithosuchidae was a widespread family of facultatively bipedal pseudosuchians with adaptations for scavenging. Riojasuchus is notable as one of the youngest and most complete members of the family. The type and only known species, Riojasuchus tenuisceps, was named and described by José Bonaparte in 1967. It was one of the first of many well-preserved Triassic archosaurs to be discovered in Argentina. The holotype specimen, PVL 3827, was found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina.

<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>Erythrosuchus</i> Extinct genus of reptiles

Erythrosuchus is an extinct genus of archosauriform reptiles from the Triassic of South Africa. Remains have been found from the Cynognathus Assemblage Zone of the Beaufort Group in the Karoo of South Africa.

<i>Terrestrisuchus</i> Genus of terrestrial crocodylomorph

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.

Orthosuchus is an extinct genus of crocodyliform that lived during the Early Jurassic, about 196 million years ago. It was first discovered in 1963 in the Red Beds Formation in the Qacha's Nek Province of Lesotho, southern Africa. The characteristics showed on its postcranial skeleton and the skull indicated that it is a crocodyliform. The finding is significant since some of the characteristics found on this specimen were believed to be absent until Jurassic.

<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.

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

Yonghesuchus is an extinct genus of Late Triassic archosaur reptile. Remains have been found from the early Late Triassic Tongchuan Formation in Shanxi, China. It is named after Yonghe County, the county where fossils were found. Currently only one species, Y. sangbiensis, is known. The specific name refers to Sangbi Creek, as fossils were found in one of its banks.

<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.

<i>Daemonosaurus</i> Genus of reptiles (fossil)

Daemonosaurus is an extinct genus of possible theropod dinosaur from the Late Triassic of New Mexico. The only known fossil is a skull and neck fragments from deposits of the latest Triassic Chinle Formation at Ghost Ranch. Daemonosaurus was an unusual dinosaur with a short skull and large, fang-like teeth. It lived alongside early neotheropods such as Coelophysis, which would have been among the most common dinosaurs by the end of the Triassic. However, Daemonosaurus retains several plesiomorphic ("primitive") traits of the snout, and it likely lies outside the clade Neotheropoda. It may be considered a late-surviving basal theropod or non-theropod basal saurischian, possibly allied to other early predatory dinosaurs such as herrerasaurids or Tawa.

<i>Smok wawelski</i> Extinct species of reptiles

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

Diandongosuchus is an extinct genus of archosauriform reptile, possibly a member of the Phytosauria, known from the Middle Triassic of China. The type species Diandongosuchus fuyuanensis was named in 2012 from the Zhuganpo Formation of Yunnan Province. It is a marine species that shows similarities with another Chinese Triassic species called Qianosuchus mixtus, although it has fewer adaptations toward marine life. It was originally classified as the basal-most member of the pseudosuchian clade Poposauroidea. However, a subsequent study conducted by Stocker et al. indicated it to be the basalmost known phytosaur instead.

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

Avicranium is a genus of extinct drepanosaur reptile known from the Chinle Formation of the late Triassic. The type species of Avicranium is Avicranium renestoi. "Avicranium" is Latin for "bird cranium", in reference to its unusual bird-like skull, while "renestoi" references Silvio Renesto, a paleontologist known for studies of Italian drepanosaurs.

References

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