''Stagonosuchus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

loricata Loricata is a clade of archosaur reptiles that includes crocodilians and some of their Triassic relatives, such as '' Postosuchus'' and ''Prestosuchus''. More specifically, Loricata includes Crocodylomorpha (the persistent archosaur subset which ...

n, or possibly a species of ''

Prestosuchus ''Prestosuchus'' (meaning "Prestes crocodile") is an extinct genus of pseudosuchian in the group Loricata, which also includes '' Saurosuchus'' and '' Postosuchus''. It has historically been referred to as a " rauisuchian", and was the defining ...

''. Fossils have been found from the

Late Triassic The Late Triassic is the third and final epoch of the Triassic Period in the geologic time scale, spanning the time between Ma and Ma (million years ago). It is preceded by the Middle Triassic Epoch and followed by the Early Jurassic Epoch. ...

Manda Formation The Manda Formation (also known as the Manda Beds) is a Middle Triassic (Anisian?) or possibly Late Triassic (Carnian?) geologic formation in Tanzania. It preserves fossils of many terrestrial vertebrates from the Triassic, including some of the e ...

Tanzania Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands ...

that are

Anisian In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from million years ago until million years ago. The Anisian Age succeeds the Olenekian Age (part of the Lower Triassic ...

in age. Unlike other rauisuchians, which have a prominent ridge on the ilium called the supra-

acetabular The acetabulum (), also called the cotyloid cavity, is a concave surface of the pelvis. The head of the femur meets with the pelvis at the acetabulum, forming the hip joint. Structure There are three bones of the ''os coxae'' (hip bone) that ...

buttress that overlies the

femur The femur (; ), or thigh bone, is the proximal bone of the hindlimb in tetrapod vertebrates. The head of the femur articulates with the acetabulum in the pelvic bone forming the hip joint, while the distal part of the femur articulates wit ...

, ''Stagonosuchus'' possesses only a slight thickening on the surface of the bone. In ''Stagonosuchus'', the pubis is broad and plate like, while in other genera it is narrower and may have a prominent "foot" like that of some

theropod Theropoda (; ), whose members are known as theropods, is a dinosaur clade that is characterized by hollow bones and three toes and claws on each limb. Theropods are generally classed as a group of saurischian dinosaurs. They were ancestrally c ...

dinosaur Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the evolution of dinosaurs is t ...

s. The centra of the

vertebrae The spinal column, a defining synapomorphy shared by nearly all vertebrates, Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristi ...

are constricted to some extent, though not as much as in other rauisuchians such as ''

Saurosuchus ''Saurosuchus'' (meaning "lizard crocodile") is an extinct genus of large loricatan pseudosuchian archosaur that lived in South America during the Late Triassic period. It was a heavy, ground-dwelling, quadrupedal carnivore, likely being the ape ...

''. In the vertebrae, the neural canals (through which the

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the sp ...

would pass) extend into the centra, forming deep concavities. A wide articulation between the hyposphene and hypantrum in successive vertebrae prevented any lateral movement of the spine. A small accessory

neural spine The spinal column, a defining synapomorphy shared by nearly all vertebrates,Hagfish are believed to have secondarily lost their spinal column is a moderately flexible series of vertebrae (singular vertebra), each constituting a characteristic ...

projects near the larger main spine, possibly as an extra attachment for bracing ligaments. ''Stagonosuchus'' also has many laminae, or ridges of bone on the vertebrae. Friedrich von Huene, who named the genus in 1938, first classified ''Stagonosuchus'' as a rauisuchid. In 1967,

Alfred Romer Alfred Sherwood Romer (December 28, 1894 – November 5, 1973) was an American paleontologist and biologist and a specialist in vertebrate evolution. Biography Alfred Romer was born in White Plains, New York, the son of Harry Houston Romer an ...

placed ''Stagonosuchus'' in the newly erected

family Family (from la, familia) is a group of people related either by consanguinity (by recognized birth) or affinity (by marriage or other relationship). The purpose of the family is to maintain the well-being of its members and of society. Idea ...

Prestosuchidae Prestosuchidae (in its widest usage) is a polyphyletic grouping of carnivorous archosaurs that lived during the Triassic. They were large active terrestrial apex predators, ranging from around in length. They succeeded the Erythrosuchidae as th ...

. However, this was likely due to the close similarities shared between the two families which made classification difficult. ''Stagonosuchus'' has since been considered a rauisuchid. A 2010 study on archosaurian phylogeny found ''Stagonosuchus'' to be outside both Rauisuchidae and Prestosuchidae in a more basal position within Rauisuchia. The study erected the name Rauisuchoidea to include it and other basal taxa that were closely related to rauisuchids and prestosuchids, including ''

Ticinosuchus ''Ticinosuchus'' is an extinct genus of suchian archosaur from the Middle Triassic (Anisian - Ladinian) of Switzerland and Italy. Description One of only a handful of fossil reptiles that have been found in Switzerland, ''Ticinosuchus'' ( ...

'' (traditionally thought to be a prestosuchid) and ''

Arganasuchus ''Arganasuchus'' is an extinct genus of "rauisuchian" (loricatan) archosaur. It is known from a single species, ''Arganasuchus dutuiti''. Fossils of this genus have been found in Upper Triassic rocks of the Argana Basin, Morocco. Though its rema ...

'' and ''

Fasolasuchus ''Fasolasuchus'' is an extinct genus of loricatan. Fossils have been found in the Los Colorados Formation of the Ischigualasto-Villa Unión Basin in northwestern Argentina that date back to the Norian stage of the Late Triassic, making it one of ...

'' (previously considered rauisuchids). A 2011 study found ''Ticinosuchus'' to be the closest relative of ''Stagonosuchus'' despite a conspicuous difference in size between the two forms (''Ticinosuchus'' is much more gracile than the larger ''Stagonosuchus''). A 2020 study argued that ''Stagonosuchus'' was a second species of ''

'', ''Prestosuchus nyassicus''.

References

Rauisuchids Anisian life Middle Triassic reptiles of Africa Triassic Tanzania Fossils of Tanzania Fossil taxa described in 1938 Prehistoric pseudosuchian genera {{triassic-reptile-stub