Stagonosuchus
Encyclopedia
Stagonosuchus is an extinct genus
of rauisuchid rauisuchia
n. Fossils have been found from the Late Triassic
Manda Formation in Tanzania
that are Anisian
in age.
Unlike other rauisuchians, which have a prominent ridge on the illium called the supra-acetabular butress that overlies the femur
, 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
s.
The centra of the vertebrae 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
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.
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
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).
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of rauisuchid rauisuchia
Rauisuchia
Rauisuchia is a group of predatory and mostly large Triassic archosaurs. As a clade, Rauisuchia includes these Triassic forms and all crocodylomorphs, which are descendants of Triassic rauisuchians. The group in its traditional sense is paraphyletic, because it does not include crocodylomorph...
n. Fossils have been found from the Late Triassic
Late Triassic
The Late Triassic is in the geologic timescale the third and final of three epochs of the Triassic period. The corresponding series is known as the Upper Triassic. In the past it was sometimes called the Keuper, after a German lithostratigraphic group that has a roughly corresponding age...
Manda Formation in Tanzania
Tanzania
The United Republic of Tanzania is a country in East Africa bordered by Kenya and Uganda to the north, Rwanda, Burundi, and the Democratic Republic of the Congo to the west, and Zambia, Malawi, and Mozambique to the south. The country's eastern borders lie on the Indian Ocean.Tanzania is a state...
that are Anisian
Anisian
In the geologic timescale, the Anisian is the lower stage or earliest age of the Middle Triassic series or epoch and lasted from 245 million years ago until 237 million years ago, approximately...
in age.
Unlike other rauisuchians, which have a prominent ridge on the illium called the supra-acetabular butress that overlies the femur
Femur
The femur , or thigh bone, is the most proximal bone of the leg in tetrapod vertebrates capable of walking or jumping, such as most land mammals, birds, many reptiles such as lizards, and amphibians such as frogs. In vertebrates with four legs such as dogs and horses, the femur is found only in...
, Stagonosuchus possesses only a slight thickening on the surface of the bone. In Stagonosuchus, the pubis
Pubis
Pubis may refer to:* Pubis * Mons pubis, a padding of fat that protects the pubis bone...
is broad and plate like, while in other genera it is narrower and may have a prominent "foot" like that of some theropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
s.
The centra of the vertebrae are constricted to some extent, though not as much as in other rauisuchians such as Saurosuchus
Saurosuchus
Saurosuchus is an extinct genus of rauisuchian archosaur in the family Prestosuchidae. With a length of around 7 m , it was the largest rauisuchian, except perhaps for the less well known Fasolasuchus. Like other rauisuchians, Saurosuchus walked on four fully erect limbs...
. In the vertebrae, the neural canals (through which the spinal cord
Spinal cord
The spinal cord is a long, thin, tubular bundle of nervous tissue and support cells that extends from the brain . The brain and spinal cord together make up the central nervous system...
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
Lamina of the vertebral arch
The laminæ are two broad plates, extending dorsally and medially from the pedicles, fusing to complete the roof of the vertebral arch.Their upper borders and the lower parts of their anterior surfaces are rough for the attachment of the ligamenta flava....
, or ridges of bone on the vertebrae.
Friedrich von Huene
Friedrich von Huene
Friedrich von Huene was a German paleontologist who named more dinosaurs in the early 20th century than anyone else in Europe.-Biography:...
, who named the genus in 1938, first classified Stagonosuchus as a rauisuchid. In 1967, Alfred Romer
Alfred Romer
Alfred Sherwood Romer was an American paleontologist and comparative anatomist and a specialist in vertebrate evolution.-Biography:...
placed Stagonosuchus in the newly erected family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Prestosuchidae
Prestosuchidae
Prestosuchids were a group of Triassic carnivorous archosaurs. They were large active terrestrial apex predators, ranging from around in length. They succeeded the Erythrosuchidae as the largest archosaurs of their time...
. 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
Ticinosuchus is an extinct genus of rauisuchian archosaur from the Middle Triassic of Switzerland and Italy.Ticinosuchus was about long, and its whole body, even the belly, was covered in thick, armoured scutes. The structure of the hips shows that its legs were placed under the body almost...
(traditionally thought to be a prestosuchid) and Arganasuchus
Arganasuchus
Arganasuchus is a genus of rauisuchid archosaur. Its fossils have been found in Upper Triassic rocks of the Argana Basin, Morocco. It is based on remains found in the 1970s and initially thought to belong to the rauisuchian Ticinosuchus. Bones recovered include part of the upper jaws, neck...
and Fasolasuchus
Fasolasuchus
Fasolasuchus is an extinct genus of rauisuchid rauisuchian. Fossils have been found from Argentina that date back to the Rhaetian stage of the Late Triassic, making it one of the last rauisuchians to have existed before the order went extinct at the end of the Triassic...
(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).