''Scythosuchus'' is an extinct genus of

rauisuchid Rauisuchidae is a group of large (up to or more) predatory Triassic archosaurs. There is some disagreement over which genera should be included in Rauisuchidae and which should be in the related Prestosuchidae and Poposauridae, and indeed whethe ...

. Remains have been found from Olenekian-age

Lower Triassic The Early Triassic is the first of three epochs of the Triassic Period of the geologic timescale. It spans the time between Ma and Ma (million years ago). Rocks from this epoch are collectively known as the Lower Triassic Series, which is a un ...

beds in

Russia Russia (, , ), or the Russian Federation, is a transcontinental country spanning Eastern Europe and Northern Asia. It is the largest country in the world, with its internationally recognised territory covering , and encompassing one-eig ...

, hence the name meaning '

Scythian The Scythians or Scyths, and sometimes also referred to as the Classical Scythians and the Pontic Scythians, were an ancient Eastern * : "In modern scholarship the name 'Sakas' is reserved for the ancient tribes of northern and eastern Centra ...

crocodile'. The type and only species is ''S. basileus'', described in 1999. ''Scythosuchus'' was between 2 and 3 metres long, and relatively heavily built. It is known from a partial

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, th ...

, much of the spine, a fragment of the humerus and most of the hind leg and foot. It may have been the same animal as ''

Tsylmosuchus ''Tsylmosuchus'' is an extinct genus of potentially dubious ctenosauriscid archosauriform reptile known from Western Russia. Fossils referred to ''Tsylmosuchus'' occurred over a wide area in sediments corresponding to the Induan and Olenekian ...

''.

Features

Skull

The skull material known is fragmentary, with a few parts of the cranium, the maxilla and some of the rostrum, and several examples of teeth. The

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. T ...

is long, as is the preorbital fenestra just above it, and has a break indicating that there was probably a large medial process. The whole snout was slightly elongated but quite narrow. The blade-like teeth are laterally compressed and serrated, with a slight backwards curve, and would have been excellent for slicing through flesh, clearly indicating that ''Scythosuchus'' was a carnivore like other rauisuchids. The cranium is relatively small, and the postorbital bone is stout and thick with some rugosities in the central area. All of the squamosal processes are heavy and well-developed. The

lower jaw In anatomy, the mandible, lower jaw or jawbone is the largest, strongest and lowest bone in the human facial skeleton. It forms the lower jaw and holds the lower teeth in place. The mandible sits beneath the maxilla. It is the only movable bone ...

is thick and has very expanded articular areas, possibly indicating a powerful bite as it would have been quite difficult for a struggling prey animal to break free.

Vertebrae

The cervical vertebrae are slightly elongated, with the

centra Centra is a convenience shop chain that operates throughout Ireland. The chain operates as a symbol group owned by Musgrave Group, the food wholesaler, meaning the stores are all owned by individual franchisees. The chain has three different ...

constricted between the wide articular surfaces. These articular surfaces are rounded. The zygapophyses have large articular surfaces oriented obliquely. The centra are approximately 1.2 times as long as they are high, and the

neural spines 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 ...

are also very low and poorly-developed, with a slightly widened and thickened tip making them top-heavy. As the vertebrae move back from the skull, the neural spines grow thicker, heavier and more rugose at the dorsal ends until they resemble

osteoderm 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 (extinc ...

s. (They are not osteoderms as these were paired in the Rauisuchia and not fused to the vertebrae - none have been identified for this species.) The

thoracic 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 ...

look quite similar to the cervical vertebrae, with lengthened centra and heavy rugose tips to their neural spines. However, the neural spines themselves are much longer than those on the cervical vertebrae, and by the posterior thoracic vertebrae are also relatively narrow. The centra have perfectly round articular facets and are slightly constricted in the centre. The caudal vertebrae also have lengthened centra, especially at the posterior end of the tail, and these grow longer and longer posteriorly. The articular facets are also tall and narrow, rather than perfectly round. The neural spines are much less rugose and heavy at the tips, but are short and thick, with a slight tilt backwards, and located on the posterior part of the centra.

Forelimb

Only the humerus is known, and of that only a fragment with most of the proximal end. This is strongly expanded, narrowing steeply and indicating that the main length of the bone may be rather slender.

Pelvis and hindlimb

A fragmentary ilium is all that is known from the pelvis, with a thick anterior edge and a well-developed dorsal process. The

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 wit ...

is much better known, as several specimens have been found, and was sigmoidal with weak lateral compression. A

trochanter A trochanter is a tubercle of the femur near its joint with the hip bone. In humans and most mammals, the trochanters serve as important muscle attachment sites. Humans are known to have three trochanters, though the anatomic "normal" includes ...

projects from near the proximal end of the bone and is relatively close to it. The

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 ...

is well preserved, as it is relatively stout as well as being lengthened, and twists slightly from proximal to distal end. The proximal end is also more oval and the distal end almost perfectly round. There are fragments of

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 i ...

known; these indicate that this was also rather stout. The

calcaneum In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is the point of the hock. ...

is short and slightly L-shaped, with a calcaneum tuber projecting to the rear and side. Rugosities on this indicate attachments for the calf muscles. There are several facets on the calcaneum for other bones of the foot, most noticeably for the

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 ...

and with smaller ones for the tarsals. The overall shape of the calcaneum indicates an ankle joint intermediate between thecodonts and

crocodilia 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 livi ...

ns.

References

Early Triassic reptiles of Asia Rauisuchids Fossil taxa described in 1999 Prehistoric pseudosuchian genera {{triassic-reptile-stub