''Stagonosuchus'' is an extinct

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

paracrocodylomorph 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. Paracrocodylomor ...

, possibly a

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 synonymous with ''

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 mem ...

'' or a

poposauroid 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 "rauisuchian ...

. Fossils have been found from the

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

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

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

that are

Anisian In the geologic timescale, the Anisian is the lower stage (stratigraphy), stage or earliest geologic age, age of the Middle Triassic series (stratigraphy), series or geologic epoch, epoch and lasted from million years ago until million years ag ...

in age.

Description

Unlike other rauisuchians, which have a prominent ridge on the ilium called the supra- acetabular buttress that overlies the

femur The femur (; : femurs or femora ), or thigh bone is the only long bone, bone in the thigh — the region of the lower limb between the hip and the knee. In many quadrupeds, four-legged animals the femur is the upper bone of the hindleg. The Femo ...

, ''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 (; from ancient Greek , (''therion'') "wild beast"; , (''pous, podos'') "foot"">wiktionary:ποδός"> (''pous, podos'') "foot" is one of the three major groups (clades) of dinosaurs, alongside Ornithischia and Sauropodom ...

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

s. The centra of the

vertebrae Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

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 archosaurs that lived in South America during the Late Triassic period. It was a heavy, ground-dwelling, quadrupedal carnivore, likely being the a ...

''. 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 that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...

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 Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...

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.

Classification

Friedrich von Huene Baron Friedrich Richard von Hoyningen-Huene (22 March 1875 – 4 April 1969) was a German nobleman paleontologist who described a large number of dinosaurs, more than anyone else in 20th-century Europe. He studied a range of Permo-Carbonife ...

, 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 ) is a Social group, group of people related either by consanguinity (by recognized birth) or Affinity (law), affinity (by marriage or other relationship). It forms the basis for social order. Ideally, families offer predictabili ...

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'' (mea ...

'' (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 re ...

'' 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 o ...

'' (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''. However, a study from the same year did not recover both as sister taxa, and the 2024 phylogenetic analysis recovered ''Stagonosuchus'' outside Loricata and suggested that it could be included within

Poposauroidea Poposauroidea is a clade of advanced Pseudosuchian, pseudosuchians. It includes poposaurids, Shuvosaurinae, shuvosaurids, ctenosauriscids, and other unusual pseudosuchians such as ''Qianosuchus'' and ''Lotosaurus''. It excludes most large predato ...

instead.

References

{{Taxonbar, from=Q7596967 Loricata Anisian life Middle Triassic reptiles of Africa Triassic Tanzania Fossils of Tanzania Fossil taxa described in 1938 Prehistoric pseudosuchian genera