''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 ...

of paracrocodylomorph, possibly a loricatan synonymous with '' Prestosuchus'' or a poposauroid. 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 in

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

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''. 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 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, who named the genus in 1938, first classified ''Stagonosuchus'' as a rauisuchid. In 1967, Alfred Romer 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. 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'' (traditionally thought to be a prestosuchid) and '' Arganasuchus'' and '' Fasolasuchus'' (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'', ''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 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