''Saurosuchus'' (meaning "lizard crocodile") is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of large

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 ...

pseudosuchian Pseudosuchia is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs". Prior to ...

archosaur Archosauria () is a clade of diapsids, with birds and crocodilians as the only living representatives. Archosaurs are broadly classified as reptiles, in the cladistic sense of the term which includes birds. Extinct archosaurs include non-avian d ...

that lived in

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...

during 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 ...

period. It was a heavy, ground-dwelling,

quadrupedal Quadrupedalism is a form of locomotion where four limbs are used to bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four limbs is said to be a quadruped (from Latin ''quattuor' ...

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant whose food and energy requirements derive from animal tissues (mainly muscle, fat and other sof ...

, likely being the

apex predator An apex predator, also known as a top predator, is a predator at the top of a food chain, without natural predators of its own. Apex predators are usually defined in terms of trophic dynamics, meaning that they occupy the highest trophic lev ...

in the

Ischigualasto Formation The Ischigualasto Formation is a Late Triassic fossiliferous formation and Lagerstätte in the Ischigualasto-Villa Unión Basin of the southwestern La Rioja Province and northeastern San Juan Province in northwestern Argentina. The formation da ...

Discovery and naming

The

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

, PVL 206, was discovered by Galileo J. Scaglia and Leocadio Soria in 1957, lying in a greenish

sandstone Sandstone is a clastic sedimentary rock composed mainly of sand-sized (0.0625 to 2 mm) silicate grains. Sandstones comprise about 20–25% of all sedimentary rocks. Most sandstone is composed of quartz or feldspar (both silicates) ...

on the Cancha de Bochas Member of the

in the

Ischigualasto-Villa Unión Basin The Ischigualasto-Villa Unión Basin ( es, Cuenca de Ischigualasto-Villa Unión) is a small sedimentary basin located in the Argentine Northwest, Argentina. It is located in the southwestern part of La Rioja Province and the northeastern part of ...

in northwestern

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the second-largest country in South America after Brazil, th ...

. It consists of a nearly complete, but deformed

skull The skull is a bone protective cavity for the brain. The skull is composed of four types of bone i.e., cranial bones, facial bones, ear ossicles and hyoid bone. However two parts are more prominent: the cranium and the mandible. In humans, the ...

. ''Saurosuchus'' was formally described and named later in

1959 Events January * January 1 - Cuba: Fulgencio Batista flees Havana when the forces of Fidel Castro advance. * January 2 - Lunar probe Luna 1 was the first man-made object to attain escape velocity from Earth. It reached the vicinity of E ...

by Osvaldo. A. Reig. The generic name, ''Saurosuchus'', is derived from the

Greek Greek may refer to: Greece Anything of, from, or related to Greece, a country in Southern Europe: *Greeks, an ethnic group. *Greek language, a branch of the Indo-European language family. **Proto-Greek language, the assumed last common ancestor ...

(, meaning lizard) and (, meaning crocodile). The specific name, ''galilei'', is in honour to Galileo J. Scaglia, who unearthed and prepared the holotype.

Referred specimens

''Saurosuchus'' is known from numerous specimens coming from the Ischigualasto Formation. Apart from the holotype, it was identified another individual: specimen PVL 2198; consisting of a partial

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

, left ilium, right and left

ischium The ischium () form ...

, eleven

dorsal vertebrae In vertebrates, thoracic vertebrae compose the middle segment of the vertebral column, between the cervical vertebrae and the lumbar vertebrae. In humans, there are twelve thoracic vertebrae and they are intermediate in size between the cervical ...

osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, temnospondyls (extinct ...

ribs The rib cage, as an enclosure that comprises the ribs, vertebral column and sternum in the thorax of most vertebrates, protects vital organs such as the heart, lungs and great vessels. The sternum, together known as the thoracic cage, is a semi- ...

and

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, tear ...

. Sill referred additional specimens, PVL 2557, 2472 and 2267. The specimen PVL 2557 consists of two dorsal vertebrae, right and left sacrals, nine

caudal 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 characteristic ...

, right ilium, ischium and partial pubis, right

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 with ...

tibia The tibia (; ), also known as the shinbone or shankbone, is the larger, stronger, and anterior (frontal) of the two bones in the leg below the knee in vertebrates (the other being the fibula, behind and to the outside of the tibia); it connects ...

fibula The fibula or calf bone is a leg bone on the lateral side of the tibia, to which it is connected above and below. It is the smaller of the two bones and, in proportion to its length, the most slender of all the long bones. Its upper extremity is ...

, tarsus and pes, ribs and

chevrons Chevron (often relating to V-shaped patterns) may refer to: Science and technology * Chevron (aerospace), sawtooth patterns on some jet engines * Chevron (anatomy), a bone * ''Eulithis testata'', a moth * Chevron (geology), a fold in rock lay ...

. PVL 2472 compromises one

cervical vertebra In tetrapods, cervical vertebrae (singular: vertebra) are the vertebrae of the neck, immediately below the skull. Truncal vertebrae (divided into thoracic and lumbar vertebrae in mammals) lie caudal (toward the tail) of cervical vertebrae. In sau ...

, tibia and

astragalus ''Astragalus'' is a large genus of over 3,000 species of herbs and small shrubs, belonging to the legume family Fabaceae and the subfamily Faboideae. It is the largest genus of plants in terms of described species. The genus is native to tempe ...

. Lastly, PVL 2267 is composed by a fragmented ilium, femur, tibia, fibula, a tarsus and a partial pes. In 2010, during the redescription of the skull of ''Saurosuchus'', Alcober referred and described the immature specimen PVSJ 32; consisting of a complete skull, complete cervical and dorsal vertebral series, four anterior caudal vertebrae, ribs and two dorsal osteoderm rows. The postcranial remains of this specimen, were properly described by Trotteyn et al. 2011. Here, more specimens of ''Saurosuchus'' were referred: PVSJ 369, 675 and 615. In addition to this, the previous specimens PVL 2472 and PVL 2267 were excluded, both of them being not referable to ''Saurosuchus''. ''Saurosuchus'' was also reported from the

Chinle Formation The Chinle Formation is an Upper Triassic continental geological formation of fluvial, lacustrine, and palustrine to eolian deposits spread across the U.S. states of Nevada, Utah, northern Arizona, western New Mexico, and western Colorado. In Ne ...

Arizona Arizona ( ; nv, Hoozdo Hahoodzo ; ood, Alĭ ṣonak ) is a state in the Southwestern United States. It is the 6th largest and the 14th most populous of the 50 states. Its capital and largest city is Phoenix. Arizona is part of the Fou ...

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 "Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians ...

Description

Initially, ''Saurosuchus'' was estimated at long with a weight over . However, a complete skeleton is not known, and size estimates range from up to in total body length.This would make it the second-largest "Rauisuchian", after the enormous ''

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 ...

''. 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. 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 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 and are part of the dermatocranium. In comparati ...

and maxilla are somewhat pitted. Pitting is also seen in aquatic

phytosaur Phytosaurs (Φυτόσαυροι in greek) are an extinct group of large, mostly semiaquatic Late Triassic archosauriform reptiles. Phytosaurs belong to the order Phytosauria. Phytosauria and Phytosauridae are often considered to be equivalent ...

s and

crocodilian Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period ( Cenomanian stage) and are the closest living ...

s, but the ridges and grooves are deeper and much more extensive across the skulls of these forms. The

frontal bone The frontal bone is a bone in the human skull. The bone consists of two portions.''Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bony part of the forehead, par ...

s, located at the top of the skull, are enlarged to form thick ridges over the eyes. As in more evolved rauisuchians, a small rod projects down from the

lacrimal bone The lacrimal bone is a small and fragile bone of the facial skeleton; it is roughly the size of the little fingernail. It is situated at the front part of the medial wall of the orbit. It has two surfaces and four borders. Several bony landmarks of ...

in front of the eye, but it does not attach firmly to the

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. Anatomy ...

bone below it. Ridges along the upper surface of the

supraoccipital bone The occipital bone () is a cranial dermal bone and the main bone of the occiput (back and lower part of the skull). It is trapezoidal in shape and curved on itself like a shallow dish. The occipital bone overlies the occipital lobes of the cereb ...

at the back of the skull are attachment points for strong neck ligaments. The cervical vertebrae are shortened and robust, forming a strong neck.

Classification

''Saurosuchus'' was considered a member of the

Rauisuchia "Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilia ...

, although now it is considered part of the more basal

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 ...

, a

clade A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, ...

comprising both Rauisuchia and the true

crocodylia Crocodilia (or Crocodylia, both ) is an order of mostly large, predatory, semiaquatic reptiles, known as crocodilians. They first appeared 95 million years ago in the Late Cretaceous period (Cenomanian stage) and are the closest living ...

ns. Below is the

cladogram A cladogram (from Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an evolutionary tree because it does not show how ancestors are related to d ...

of the Loricata conducted by Nesbitt 2011:

Paleoecology

''Saurosuchus'' was unearthed in the Cancha de Bochas Member from the

, being the major

predator Predation is a biological interaction where one organism, the predator, kills and eats another organism, its prey. It is one of a family of common feeding behaviours that includes parasitism and micropredation (which usually do not kill th ...

on its environment. The Ischigualasto Formation was dominated by

fluvial In geography and geology, fluvial processes are associated with rivers and streams and the deposits and landforms created by them. When the stream or rivers are associated with glaciers, ice sheets, or ice caps, the term glaciofluvial or fluviog ...

and

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

environments with strongly seasonal rainfalls. Interlayered

volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, created during volcano, volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used t ...

layers above the base and below the top of the formation provide chronostratigraphic control and have yielded ages of 231.4 ± 0.3 Ma and 227 ± 0.9 Ma respectively.

Contemporaneous fauna

Animals that lived alongside included numerous non-dinosaurian tetrapods, as well as basal dinosauromorphs. Notable paleofauna that were contemporaneous with ''Saurosuchus'' in the Cancha de Bochas Member include: ''

Hyperodapedon ''Hyperodapedon'' is a genus of rhynchosaurs (beaked, archosaur-like reptiles) from the Triassic, Late Triassic period (Carnian stage). Fossils of the genus have been found in Africa, Asia, Europe and North and South America. Its first discovery ...

'', ''

Exaeretodon ''Exaeretodon'' is an extinct genus of fairly large, low-slung traversodontid cynodonts from the southern parts of Pangea. Four species are known, from various formations. ''E. argentinus'' is from the Carnian-age (Late Triassic) Cancha de Boch ...

'', ''

Herrerasaurus ''Herrerasaurus'' is a genus of saurischian dinosaur from the Late Triassic period. This genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the rancher who discovered the first specimen in ...

'', ''

Sillosuchus ''Sillosuchus'' is a genus of shuvosaurid poposauroid archosaur that lived in South America during the Late Triassic period. Shuvosaurids were an unusual family of reptiles belonging to the group Poposauroidea; although their closest modern relati ...

'', ''

Eoraptor ''Eoraptor'' () is a genus of small, lightly built, basal sauropodomorph. One of the earliest-known dinosaurs, it lived approximately 231 to 228 million years ago, during the Late Triassic in Western Gondwana, in the region that is now northwest ...

'', ''

Trialestes ''Trialestes'' is an extinct genus of Late Triassic (Carnian) crocodylomorphs that lived in South America. It has been classified as a dinosaur in the past due it being adapted as a terrestrial, running carnivore. It is classified in Sphenosuchi ...

'', ''

Aetosauroides ''Aetosauroides'' (meaning "''Aetosaurus''-like") is an extinct genus of aetosaur from the Late Triassic of South America. It is one of four aetosaurs known from South America, the others being ''Neoaetosauroides'', '' Chilenosuchus'' and ''Aetob ...

'' and ''

Ischigualastia ''Ischigualastia'' is an extinct genus of large dicynodont therapsids that lived during the Late Carnian age and the Early Norian age of the Late Triassic Period. The genus was found in and named after the Ischigualasto Formation (Cancha de Boc ...

''. ''Herrerasaurus'' with ''Saurosuchus'', are some of the most common predators in the formation, with numerous specimens and remains.

References

External links

''Saurosuchus galilei''
at DigiMorph
''Saurosuchus''
at Paleofile.com (archived copy)
ICS 2018 Timescale
{{Taxonbar, from=Q137131 Paracrocodylomorphs Late Triassic pseudosuchians Carnian genera Late Triassic reptiles of South America Triassic Argentina Fossils of Argentina Ischigualasto Formation Fossil taxa described in 1959 Prehistoric pseudosuchian genera

Discovery and naming

Referred specimens

Description

Classification

Paleoecology

Contemporaneous fauna

See also

References

External links