''Eryosuchus'' is an extinct

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nom ...

of capitosauroid

temnospondyl Temnospondyli (from Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') is a diverse order of small to giant tetrapods—often considered primitive amphibians—that flourished worldwide during the Carbo ...

amphibian from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epochs of the Triassic period or the middle of three series in which the Triassic system is divided in chronostratigraphy. The Middle Triassic spans the time between Ma and ...

of northern

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 ...

. It was a very large

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 ...

: the largest specimen known could reach up to 3.5 m (11.5 ft) in length, with a

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 ...

over 1 m long.

History of study

''Eryosuchus'' was named by Ochev (1966) based on the type species, ''E. tverdochlebovi'' from exposures of the Donguz Formation in Orenburgskaya Oblast. In the same publication, Ochev also named ''E. garjainovi'' and ''E. antiquus'', both from the same formation and oblast as ''E. tverdochlebovi''. Several other species previously placed in other genera have sometimes been placed in ''Eryosuchus'', such as "''Stanocephalosaurus''" ''pronus'' from Tanzania and ''"''Stanocephalosaurus" ''rajareddyi'' from India, but this is largely disputed, as is the validity of ''E. antiquus'', which is only based on a lower jaw fragment. These species, as well as more confidently assigned species of ''Eryosuchus,'' were sometimes placed in the expansive genera ''Parotosaurus''/''

Parotosuchus ''Parotosuchus'' is an extinct genus of capitosaurian temnospondyl amphibians within the family Mastodonsauridae. Fossils are known from the Early Triassic of Europe, Africa, Australia, and Antarctica. It was about long and likely lived in aqua ...

'', which underscores the complexities of capitosaur taxonomy and the role of biogeography in formalizing such taxonomy. In the most restrictive concept of ''Eryosuchus'' (that of Schoch & Milner, 2000, and most other authors), ''Eryosuchus'' is exclusively a Russian taxon. Morales (1988) mentioned a possible new species of ''Eryosuchus'' that would represent the largest known, with an uncatalogued skull exceeding 1 m in length that would be one of the largest known temnospondyls; Schoch & Milner (2000) reiterated this and suggested that a description by Morales was forthcoming, but this specimen has never been described and could represent a different genus. If this specimen is not considered, the largest known specimen of ''Eryosuchus'' is only slightly more than 50 cm.

Anatomy

Competing concepts of ''Eryosuchus'' produce different summaries of diagnostic features. Schoch & Milner's concept, that of an exclusively Russian clade and that is adopted by most other workers, listed only two synapomorphies of the genus: intermediately sized orbits (larger than most capitosauroids other than mastodonsaurids) and an elongate post-glenoid area (PGA) that is shallowly concave and with a medial ridge aligned sagittally. Damiani's (2001) more expansive concept listed only laterally directed tabular horns with an antero-distal 'lappet' as apomorphic for this genus. ''Eryosuchus tverdochlebovi'' and ''E. garjainovi'' are represented by many skulls and postcranial remains, which secures their validity in contrast to ''E. antiquus'', represented by one lower jaw fragment. The two definitive species are differentiated by their relative orbit size and the length of their basicranial suture. This is one of the few capitosaurs from which fully ossified intercentra are known.

Phylogeny

Below is the phylogeny from Fortuny et al. (2011); ''E. garjainovi'' is typically used as the representative of this genus:

Biostratigraphy

The Russian framework for Triassic biostratigraphy is larged based on temnospondyls, in contrast to the South African Assemblage Zones, which are largely based on amniotes. ''Eryosuchus'' is among the taxa used to make regional correlations given its relatively common occurrence in Russia. It is thought that the ''Eryosuchus'' Fauna is at least partially correlative with the ''Cynognathus'' Assemblage Zone in South Africa.

References

{{Taxonbar, from=Q3755398 Triassic temnospondyls of Europe Middle Triassic amphibians of Europe Fossil taxa described in 1966 Prehistoric amphibian genera