''Estemmenosuchus'' (meaning "crowned crocodile" in

Greek Greek may refer to: Greece 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 ...

) 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 large, early

omnivorous An omnivore () is an animal that has the ability to eat and survive on both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize the nut ...

therapsid Therapsida is a major group of eupelycosaurian synapsids that includes mammals, their ancestors and relatives. Many of the traits today seen as unique to mammals had their origin within early therapsids, including limbs that were oriented more ...

. It is believed and interpreted to have lived during the middle part of the

Middle Permian The Guadalupian is the second and middle series/ epoch of the Permian. The Guadalupian was preceded by the Cisuralian and followed by the Lopingian. It is named after the Guadalupe Mountains of New Mexico and Texas, and dates between 272.95 ± ...

around 267 million years ago. The two species, ''E. uralensis'' and ''E. mirabilis'', are characterised by distinctive horn-like structures, which were probably used for intra-specific display. Both species of ''Estemmenosuchus'' are from the

Perm Perm or PERM may refer to: Places *Perm, Russia, a city in Russia ** Permsky District, the district **Perm Krai, a federal subject of Russia since 2005 **Perm Oblast, a former federal subject of Russia 1938–2005 **Perm Governorate, an administra ...

(or Cis-Urals) region of Russia. Two other estemmenosuchids, ''Anoplosuchus'' and ''Zopherosuchus'', are now considered females of the species ''E. uralensis''. There were many complete and incomplete skeletons found together.

Description

''Estemmenosuchus'' could reach a body length of more than . Its skull was long and massive, up to in length, and possessed several sets of large horns, somewhat similar to the antlers of a

moose The moose (in North America) or elk (in Eurasia) (''Alces alces'') is a member of the New World deer subfamily and is the only species in the genus ''Alces''. It is the largest and heaviest extant species in the deer family. Most adult ma ...

, growing upward and outward from the sides and top of the head. The animal had a sprawling posture as indicated by analysing its

shoulder joint The shoulder joint (or glenohumeral joint from Greek ''glene'', eyeball, + -''oid'', 'form of', + Latin ''humerus'', shoulder) is structurally classified as a synovial ball-and-socket joint and functionally as a diarthrosis and multiaxial joint ...

s. The skull superficially resembles that of '' Styracocephalus'', but the "horns" are formed from different bones; in ''Estemmenosuchus'' the horns are located on the frontals and protrude upward, whereas in Styracocephalus the horns are formed by the tabular and extend aft.

Species

''Estemmenosuchus'' is interpreted to have lived some 267 million years ago. Two species have been identified, from the Ocher Assemblage Zone Belebei Formation at the Ezhovo locality near Ochyor in the

region of the

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 ...

in 1960. They were found with the Biarmosuchians '' Eotitanosuchus olsoni'' and ''

Biarmosuchus tener ''Biarmosuchus'' is an extinct genus of biarmosuchian therapsids that lived around 267 mya during the Middle Permian period. ''Biarmosuchus'' was discovered in the Perm region of Russia. The first specimen was found in channel sandstone that w ...

'' in channel flood deposits of the young

Ural Mountains The Ural Mountains ( ; rus, Ура́льские го́ры, r=Uralskiye gory, p=ʊˈralʲskʲɪjə ˈɡorɨ; ba, Урал тауҙары) or simply the Urals, are a mountain range that runs approximately from north to south through western ...

. They differ in size, shape of the skull, and shape of the horns. Originally all specimens were included in ''Estemmenosuchus uralensis'', but it was since realised that there were a number of different species. However, not all palaeontologists agree that these were different species. According to Ivakhnenko (1998) ''Anoplosuchus'' and ''Zopherosuchus'' are synonyms of ''Estemmenosuchus uralensis''.

Paleobiology

Thermoregulation

It has been suggested that the animal had a fairly constant internal temperature. Its large size and compact build gave a small surface-to-volume ratio and suggests it would not gain (or lose) temperature quickly. This phenomenon is called

gigantothermy Gigantothermy (sometimes called ectothermic homeothermy or inertial homeothermy) is a phenomenon with significance in biology and paleontology, whereby large, bulky ectothermic animals are more easily able to maintain a constant, relatively high bod ...

and was probably an important factor in temperature regulation in most therapsids.

Skin

P. Chudinov reported skin impressions belonging to ''Estemmenosuchus'' in 1968. The skin was described as being " glandular" like that of a hairless mammal or a

frog A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is ...

References

External links

Palaeos
- detailed description {{Taxonbar, from=Q133120 Tapinocephalians Prehistoric therapsid genera Wordian genera Guadalupian synapsids of Europe Permian Russia Fossils of Russia Fossil taxa described in 1960