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

extinct Extinction is the termination of an organism by the death of its Endling, last member. A taxon may become Functional extinction, functionally extinct before the death of its last member if it loses the capacity to Reproduction, reproduce and ...

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 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, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...

archosaur Archosauria () or archosaurs () is a clade of diapsid sauropsid tetrapods, with birds and crocodilians being the only extant taxon, extant representatives. Although broadly classified as reptiles, which traditionally exclude birds, the cladistics ...

s that lived in South America 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 a ...

period. It was a heavy, ground-dwelling,

quadrupedal Quadrupedalism is a form of Animal locomotion, locomotion in which animals have four legs that are used to weight-bearing, bear weight and move around. An animal or machine that usually maintains a four-legged posture and moves using all four l ...

carnivore A carnivore , or meat-eater (Latin, ''caro'', genitive ''carnis'', meaning meat or "flesh" and ''vorare'' meaning "to devour"), is an animal or plant Plants are the eukaryotes that form the Kingdom (biology), kingdom Plantae; they ar ...

, likely being the

apex predator An apex predator, also known as a top predator or superpredator, 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 hig ...

in the

Ischigualasto Formation The Ischigualasto Formation is a Late Triassic geological formation in the Ischigualasto-Villa Unión Basin of southwestern La Rioja Province, Argentina, La Rioja Province and northeastern San Juan Province, Argentina, San Juan Province in northw ...

Discovery and naming

The

holotype A holotype (Latin: ''holotypus'') is a single physical example (or illustration) of an organism used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of s ...

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

sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...

on the Cancha de Bochas Member of the

in the

Ischigualasto-Villa Unión Basin The Ischigualasto-Villa Unión Basin () 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 San Juan Province. The basin borders the ...

in northwestern

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

. It consists of a nearly complete, but deformed

skull The skull, or cranium, is typically a bony enclosure around the brain of a vertebrate. In some fish, and amphibians, the skull is of cartilage. The skull is at the head end of the vertebrate. In the human, the skull comprises two prominent ...

. ''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 – Soviet lunar probe Luna 1 is the first human-made object to attain escape velocity from Earth. It reaches the ...

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

Greek Greek may refer to: 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 of all kno ...

(, meaning lizard) and (, meaning crocodile). The

specific name Specific name may refer to: * in Database management systems, a system-assigned name that is unique within a particular database In taxonomy, either of these two meanings, each with its own set of rules: * Specific name (botany), the two-part (bino ...

, ''galilei'', is in honour to Galileo J. Scaglia, who unearthed and

prepared The Scout Motto of the Scout movement is, in English, "Be Prepared", with most international branches of the group using a close translation of that phrase. These mottoes have been used by millions of Scouts around the world since 1907. Most of t ...

the holotype.

Referred specimens

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

maxilla In vertebrates, the maxilla (: maxillae ) 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 two maxil ...

, left ilium, right and left

ischium The ischium (; : is ...

, 11

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 vertebra (anatomy), vertebrae of intermediate size between the ce ...

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

ribs The rib cage or thoracic cage is an endoskeletal enclosure in the thorax of most vertebrates that comprises the ribs, vertebral column and sternum, which protect the vital organs of the thoracic cavity, such as the heart, lungs and great vessels ...

, 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 Caudal vertebrae are the vertebrae of the tail in many vertebrates. In birds, the last few caudal vertebrae fuse into the pygostyle, and in apes, including humans, the caudal vertebrae are fused into the coccyx. In many reptiles, some of the caud ...

, right ilium, ischium and partial pubis, right

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 ...

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

fibula The fibula (: fibulae or fibulas) 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. ...

, 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 la ...

. PVL 2472 compromises one

cervical vertebra In tetrapods, cervical vertebrae (: 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 sauropsid s ...

, tibia and

astragalus Astragalus may refer to: * ''Astragalus'' (plant), a large genus of herbs and small shrubs *Astragalus (bone) The talus (; Latin for ankle or ankle bone; : tali), talus bone, astragalus (), or ankle bone is one of the group of foot bones known ...

. Lastly, PVL 2267 is composed by a fragmented ilium, femur, tibia, fibula, tarsus, and 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, the previous specimens PVL 2472 and PVL 2267 were excluded, with 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 ...

Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...

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

''Saurosuchus'' was a large rauisuchian, measuring long and weighing over . Two sub-adult specimens are estimated around long and weighing approximately . This would make it one of the largest "rauisuchians", 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 o ...

''. Two rows are on 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, including land-living vertebrates. The bones are derived from dermal bone and are part of the dermatocranium. In com ...

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

phytosaur Phytosaurs (Φυτόσαυροι in Greek, meaning 'plant lizard') are an extinct group of large, mostly semiaquatic Late Triassic archosauriform or basal archosaurian reptiles. Phytosaurs belong to the order Phytosauria and are sometimes ref ...

s and

crocodilian Crocodilia () is an Order (biology), order of semiaquatic, predatory reptiles that are known as crocodilians. They first appeared during the Late Cretaceous and are the closest living relatives of birds. Crocodilians are a type of crocodylomorp ...

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

frontal bone In the human skull, the frontal bone or sincipital bone is an unpaired bone which consists of two portions.'' Gray's Anatomy'' (1918) These are the vertically oriented squamous part, and the horizontally oriented orbital part, making up the bo ...

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 bones are two small and fragile bones of the facial skeleton; they are roughly the size of the little fingernail and situated at the front part of the medial wall of the orbit. They each have two surfaces and four borders. Several bon ...

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 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 lies over the occipital lobes of the cere ...

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.

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 crocodilians ...

, although the clade is now considered paraphyletic and ''Saurosuchus'' is considered a basal member of

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 In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...

comprising "rauisuchians" as well as

crocodylomorphs Crocodylomorpha is a group of pseudosuchian archosaurs that includes the crocodilians and their extinct relatives. They were the only members of Pseudosuchia to survive the end-Triassic extinction. Extinct crocodylomorphs were considerably more ...

. Below is the

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

of the Loricata conducted by Nesbitt 2011: In more recent analyses, ''Saurosuchus'' has been found within the loricatan clade

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 ...

. The cladogram below follows a simplified version of the strict reduced consensus tree by Desojo ''et al.'' (2020):

Paleobiology

Analysis of a juvenile ''Saurosuchus'' specimen indicated that its bite force and jaw strength were relatively weak, as determined in a study by Bestwick ''et al.,'' in 2023. Its bite force when scaled up to an adult size was estimated to have been around , similar to that of modern

gharial The gharial (''Gavialis gangeticus''), also known as gavial or fish-eating crocodile, is a crocodilian in the family (biology), family Gavialidae and among the longest of all living crocodilians. Mature females are long, and males . Adult males ...

s in regards to strength, due to its relatively thinner bones compared to those of the theropod dinosaurs that would later supplant it. Although this does not account for possible changes in the development of the skull and dentition as the animal grows into adulthood. It would suggest that juvenile ''Saurosuchus'' would feed largely on softer food such as flesh and vital organs from its prey brought to it by if it's parents exhibited parental care, which it would process with its rear teeth. The teeth would be completely suitable for processing small sized prey if juveniles were not cared for by their parents. A reconstruction of the cranial endocast revealed large

olfactory bulbs The olfactory bulb (Latin: ''bulbus olfactorius'') is a grey matter, neural structure of the vertebrate forebrain involved in olfaction, the sense of odor, smell. It sends olfactory information to be further processed in the amygdala, the orbitof ...

, poorly developed

flocculus The flocculus (Latin: ''tuft of wool'', diminutive) is a small lobe of the cerebellum at the posterior border of the middle cerebellar peduncle anterior to the biventer lobule. Like other parts of the cerebellum, the flocculus is involved in moto ...

and optic lobes, and an anteroposteriorly short

lateral semicircular canal The semicircular canals are three semicircular interconnected tubes located in the innermost part of each ear, the inner ear. The three canals are the lateral, anterior and posterior semicircular canals. They are the part of the bony labyrinth, ...

, suggesting that ''Saurosuchus'' would have relied on smell instead of eyesight to track prey over long distances or at night, and that it would not have been a particularly agile predator. Furthermore, the lagena is relatively long, suggesting a broad hearing sensitivity, especially in low-frequency sounds. A hypertrophied hypophysis has also been reported for ''Saurosuchus'', which may be correlated with large size and possibly rapid growth rates, as observed in the majority of other "rauisuchians" based on bone microstructure.

Paleoecology

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

, being the major

predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...

on its environment. The Ischigualasto Formation was dominated by

fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

and

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river. Floodplains stretch from the banks of a river channel to the base of the enclosing valley, and experience flooding during periods of high Discharge (hydrolog ...

environments with strongly seasonal rainfalls. Interlayered

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

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 nondinosaurian tetrapods and basal dinosauromorphs. Notable paleofauna that were contemporaneous with ''Saurosuchus'' in the Cancha de Bochas Member include: ''

Hyperodapedon ''Hyperodapedon'' (from , 'above' and , 'pavement') is an extinct genus of rhynchosaur reptiles which lived during Triassic, Late Triassic period. Like other rhynchosaurs, it was an heavily built Archosauromorpha, archosauromorph, distantly rel ...

'', ''

Exaeretodon ''Exaeretodon'' is an Extinction, extinct genus of fairly large, low-slung traversodontid cynodonts from the southern parts of Pangea. Four species are Knowledge, known, hailing from various geologic formation, formations. ''E. argentinus'' is fr ...

'', ''

Herrerasaurus ''Herrerasaurus'' is likely a genus of saurischian dinosaur from the Late Triassic period. Measuring long and weighing around , this genus was one of the earliest dinosaurs from the fossil record. Its name means "Herrera's lizard", after the ...

'', ''

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 (phylogenetics), basal sauropodomorpha, sauropodomorph dinosaur. One of the earliest-known dinosaurs and one of the earliest sauropodomorphs, it lived approximately 231 to 228 million yea ...

'', ''

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 '' Ae ...

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

References

External links

''Saurosuchus galilei''
at

DigiMorph Digital Morphology (DigiMorph), 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 'inve ...

''Saurosuchus''
at Paleofile.com (archived copy)
ICS 2018 Timescale
{{Taxonbar, from=Q137131 Loricata 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

Paleobiology

Paleoecology

Contemporaneous fauna

See also

References

External links