Saurosuchus
Encyclopedia
Saurosuchus is an extinct genus
of rauisuchia
n archosaur
in the family
Prestosuchidae
. With a length of around 7 m (23 ft), it was the largest rauisuchian, except perhaps for the less well known Fasolasuchus
. Like other rauisuchians, Saurosuchus walked on four fully erect limbs. It lived in the Late Triassic
of Argentina
.
Saurosuchus is known from several partial skeletons collected from the Ischigualasto Formation of Argentina. The holotype
specimen consists of a complete but deformed skull, dorsal vertebrae, dorsal osteoderm
s, and parts of the pelvis
. The hind limbs, tail, neck, and scapula
e are also represented in several other skeletons. The type species
S. galilei was named in 1959. Saurosuchus was also reported from the Chinle Formation
of Arizona
in 2002 on the basis of isolated teeth and small skull fragments. The diagnostic value of these bones has been questioned in later studies, which considered them to be from an indeterminate species of rauisuchian.
Saurosuchus is one of the largest rauisuchians. The complete skeleton is not known and size estimates range from around 6 to 9 m (19.7 to 29.5 ft) in total body length. It has a deep, laterally compressed skull. The teeth are large, recurved, and serrated. The skull is wide at its back and narrows in front of the eyes. The skull roof
and maxilla
are somewhat pitted, a distinguishing feature not seen in any other rauisuchian. Pitting is also seen in aquatic phytosaur
s and crocodilians, but the ridges and grooves are deeper and much more extensive across the skulls of these forms. The frontal bone
s, located at the top of the skull, are enlarged to form thick ridges over the eyes. As in other rauisuchians, a small rod projects down from the lacrimal bone
in front of the eye, but it does not attach firmly to the jugal
bone below it. Ridges along the upper surface of the supraoccipital bone at the back of the skull are attachment points for strong neck ligaments. The cervical vertebrae are shortened and robust, forming a strong neck. Dorsal osteoderms run along the back of Saurosuchus. There are two rows to either side of the midline, with each leaf-shaped osteoderm joining tightly with the ones in front of and behind it.
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 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 archosaur
Archosaur
Archosaurs are a group of diapsid amniotes whose living representatives consist of modern birds and crocodilians. This group also includes all extinct non-avian dinosaurs, many extinct crocodilian relatives, and pterosaurs. Archosauria, the archosaur clade, is a crown group that includes the most...
in the 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...
. With a length of around 7 m (23 ft), it was the largest rauisuchian, except perhaps for the less well known 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...
. Like other rauisuchians, Saurosuchus walked on four fully erect limbs. It lived in 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...
of Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
.
Description
Holotype
A holotype is a single physical example of an organism, known to have been used when the species was formally described. It is either the single such physical example or one of several such, but explicitly designated as the holotype...
specimen consists of a complete but deformed skull, dorsal vertebrae, dorsal osteoderm
Osteoderm
Osteoderms are bony deposits forming scales, plates or other structures in the dermal layers of the skin. Osteoderms are found in many groups of extant and extinct reptiles, including lizards, various groups of dinosaurs , crocodilians, phytosaurs, aetosaurs, placodonts, and hupehsuchians...
s, and parts of the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
. The hind limbs, tail, neck, and scapula
Scapula
In anatomy, the scapula , omo, or shoulder blade, is the bone that connects the humerus with the clavicle ....
e are also represented in several other skeletons. The type species
Type species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
S. galilei was named in 1959. Saurosuchus was also reported from the Chinle Formation
Chinle Formation
The Chinle is a geologic formation that is spread across the U.S. states of northern Arizona, Nevada, Utah, western New Mexico, and western Colorado. The Chinle is controversially considered to be synonymous to the Dockum Group in eastern Colorado, eastern New Mexico, southwestern Kansas, the...
of Arizona
Arizona
Arizona ; is a state located in the southwestern region of the United States. It is also part of the western United States and the mountain west. The capital and largest city is Phoenix...
in 2002 on the basis of isolated teeth and small skull fragments. The diagnostic value of these bones has been questioned in later studies, which considered them to be from an indeterminate species of rauisuchian.
Saurosuchus is one of the largest rauisuchians. The complete skeleton is not known and size estimates range from around 6 to 9 m (19.7 to 29.5 ft) in total body length. It has a deep, laterally compressed skull. The teeth are large, recurved, and serrated. The skull is wide at its back and narrows in front of the eyes. The skull roof
Skull roof
The skull roof , or the roofing bones of the skull are a set of bones covering the brain, eyes and nostrils in bony fishes and all land living vertebrates. The bones are derived from dermal bone, hence the alternative name dermatocranium...
and maxilla
Maxilla
The maxilla is a fusion of two bones along the palatal fissure that form the upper jaw. This is similar to the mandible , which is also a fusion of two halves at the mental symphysis. Sometimes The maxilla (plural: maxillae) is a fusion of two bones along the palatal fissure that form the upper...
are somewhat pitted, a distinguishing feature not seen in any other rauisuchian. Pitting is also seen in aquatic phytosaur
Phytosaur
Phytosaurs are an extinct group of large semi-aquatic Late Triassic archosaurs. Phytosaurs belong to the family Phytosauridae and the order Phytosauria. They were long-snouted and heavily armoured, bearing a remarkable resemblance to modern crocodiles in size, appearance, and lifestyle, an example...
s and crocodilians, but the ridges and grooves are deeper and much more extensive across the skulls of these forms. The frontal bone
Frontal bone
The frontal bone is a bone in the human skull that resembles a cockleshell in form, and consists of two portions:* a vertical portion, the squama frontalis, corresponding with the region of the forehead....
s, located at the top of the skull, are enlarged to form thick ridges over the eyes. As in other rauisuchians, a small rod projects down from the lacrimal bone
Lacrimal bone
The lacrimal bone, the smallest and most fragile bone of the face, is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders.-Lateral or orbital surface:...
in front of the eye, but it does not attach firmly to the jugal
Jugal
The jugal is a skull bone found in most reptiles, amphibians, and birds. In mammals, the jugal is often called the malar or Zygomatic. It is connected to the quadratojugal and maxilla, as well as other bones, which may vary by species....
bone below it. Ridges along the upper surface of the supraoccipital bone at the back of the skull are attachment points for strong neck ligaments. The cervical vertebrae are shortened and robust, forming a strong neck. Dorsal osteoderms run along the back of Saurosuchus. There are two rows to either side of the midline, with each leaf-shaped osteoderm joining tightly with the ones in front of and behind it.
External links
- Saurosuchus galilei at DigiMorphDigiMorphDigital Morphology , part of the National Science Foundation Digital Libraries Initiative, creates and shares 2D and 3D visualizations of the internal and external structure of living and extinct vertebrates, and a growing number of 'invertebrates.'...