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

Greek Greek may refer to: 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 of all kno ...

) 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 large, early

omnivorous An omnivore () is an animal that regularly consumes significant quantities of both plant and animal matter. Obtaining energy and nutrients from plant and animal matter, omnivores digest carbohydrates, protein, fat, and fiber, and metabolize ...

therapsid. 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 ± 0. ...

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 (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

skeleton A skeleton is the structural frame that supports the body of most animals. There are several types of skeletons, including the exoskeleton, which is a rigid outer shell that holds up an organism's shape; the endoskeleton, a rigid internal fra ...

s 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 (: 'moose'; used in North America) or elk (: 'elk' or 'elks'; used in Eurasia) (''Alces alces'') is the world's tallest, largest and heaviest extant species of deer and the only species in the genus ''Alces''. It is also the tal ...

, 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 joint, synovial ball-and-socket joint and functionally as a diarthrosis and m ...

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 Perm region of the

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 ...

in 1960. They were found with the Biarmosuchians '' Eotitanosuchus olsoni'' and '' Biarmosuchus tener'' in channel flood deposits of the young

Ural Mountains The Ural Mountains ( ),; , ; , or simply the Urals, are a mountain range in Eurasia that runs north–south mostly through Russia, from the coast of the Arctic Ocean to the river Ural (river), Ural and northwestern Kazakhstan.

. 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 bo ...

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 "

gland A gland is a Cell (biology), cell or an Organ (biology), organ in an animal's body that produces and secretes different substances that the organism needs, either into the bloodstream or into a body cavity or outer surface. A gland may also funct ...

ular" like that of a hairless mammal or a

frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...

. More specifically, structured referred to as “lenses” are interpreted as glands, which would be their earliest occurrence in the fossil record if true. Melanosomes may also be preserved (one of the first recorded instances of such), as evidenced by darker areas surrounding the “lenses”. Alongside this, an osteoderm was associated with a sacrum recorded as belonging to “Anoplosuchus” (which is a junior synonym of ''Estemmenosuchus''), suggesting the animal had osteoderms embedded in its skin, similar to those of mylodontid ground sloths.

References

External links

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