''Eryosuchus'' 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 capitosauroid

temnospondyl Temnospondyli (from Greek language, Greek τέμνειν, ''temnein'' 'to cut' and σπόνδυλος, ''spondylos'' 'vertebra') or temnospondyls is a diverse ancient order (biology), order of small to giant tetrapods—often considered Labyrinth ...

from the

Middle Triassic In the geologic timescale, the Middle Triassic is the second of three epoch (geology), epochs of the Triassic period (geology), period or the middle of three series (stratigraphy), series in which the Triassic system (stratigraphy), system is di ...

of northern

Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...

. It was a very large

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 ...

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

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 ...

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 temnospondyls 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 aquatic envir ...

'', 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 In phylogenetics, an apomorphy (or derived trait) is a novel character or character state that has evolved from its ancestral form (or plesiomorphy). A synapomorphy is an apomorphy shared by two or more taxa and is therefore hypothesized to ...

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 Amniotes are tetrapod vertebrate animals belonging to the clade Amniota, a large group that comprises the vast majority of living terrestrial and semiaquatic vertebrates. Amniotes evolved from amphibious stem tetrapod ancestors during the ...

. ''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 Capitosauria Triassic temnospondyls of Europe Middle Triassic amphibians of Europe Fossil taxa described in 1966 Triassic Russia