| Eryosuchus | |
|---|---|
 | |
| E. tverdochlebovi skull | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Order: | †Temnospondyli |
| Suborder: | †Stereospondyli |
| Clade: | †Capitosauria |
| Family: | †Mastodonsauridae |
| Genus: | †Eryosuchus Otschev, 1966 |
| Species | |
Eryosuchus is anextinctgenus ofcapitosauroidtemnospondyl from theMiddle Triassic of northernRussia. It was a very largepredator: the largest specimen known could reach up to 3.5 m (11.5 ft) in length, with askull over 1 m long.[1]
Eryosuchus was named by Ochev (1966) based on the type species,E. tverdochlebovi from exposures of the Donguz Formation inOrenburgskaya Oblast.[2] In the same publication, Ochev also namedE. garjainovi andE. antiquus, both from the same formation and oblast asE. tverdochlebovi. Several other species previously placed in other genera have sometimes been placed inEryosuchus, such as "Stanocephalosaurus"pronus from Tanzania and"Stanocephalosaurus"rajareddyi from India,[3] but this is largely disputed, as is the validity ofE. antiquus, which is only based on a lower jaw fragment.[1][4][5][6][7] These species, as well as more confidently assigned species ofEryosuchus, were sometimes placed in the expansive generaParotosaurus/Parotosuchus, which underscores the complexities of capitosaur taxonomy and the role of biogeography in formalizing such taxonomy. In the most restrictive concept ofEryosuchus (that of Schoch & Milner, 2000, and most other authors),Eryosuchus is exclusively a Russian taxon. Morales (1988) mentioned a possible new species ofEryosuchus that would represent the largest known, with an uncatalogued skull exceeding 1 m in length that would be one of the largest known temnospondyls;[8] 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 ofEryosuchus is only slightly more than 50 cm.[1]
Competing concepts ofEryosuchus 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 twosynapomorphies of the genus: intermediately sized orbits (larger than most capitosauroids other thanmastodonsaurids) 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 andE. garjainovi are represented by many skulls and postcranial remains, which secures their validity in contrast toE. 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.[9]
Below is the phylogeny from Fortuny et al. (2011);E. garjainovi is typically used as the representative of this genus:[10]
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The Russian framework for Triassic biostratigraphy is larged based on temnospondyls,[11][12][13] in contrast to the South African Assemblage Zones, which are largely based onamniotes.[14]Eryosuchus is among the taxa used to make regional correlations given its relatively common occurrence in Russia. It is thought that theEryosuchus Fauna is at least partially correlative with theCynognathus Assemblage Zone in South Africa.[15][11]
