Anteosaurus

Anteosaurus Temporal range: Capitanian, 266–260 Ma PreЄ Є O S D C P T J K Pg N
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Life restoration of Anteosaurus magnificus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Order:	Therapsida
Suborder:	†Dinocephalia
Family:	†Anteosauridae
Clade:	†Anteosaurini
Genus:	†Anteosaurus
Binomial name
Anteosaurus magnificus Watson 1921
Synonyms
Genus synonymy Eccasaurus (?) Broom, 1909 Titanognathus Broili & Schröder, 1935 Dinosuchus Broom, 1936 Broomosuchus Camp, 1942 Micranteosaurus Boonstra, 1954 Paranteosaurus (?) Boonstra, 1954 Pseudanteosaurus Boonstra, 1954 Species synonymy Eccasaurus priscus (?) Broom, 1909 Anteosaurus minor Broom, 1929 Titanognathus lotzi Broili & Schröder, 1935 Dinosuchus vorsteri Broom, 1936 Broomosuchus vorsteri Camp, 1942 Anteosaurus abeli Boonstra, 1952 Anteosaurus vorsteri Boonstra, 1953 Titanosuchus lotzi Boonstra, 1953 Anteosuchus acutirostris Boonstra, 1954 Anteosaurus crassifrons Boonstra, 1954 Anteosaurus cruentus Boonstra, 1954 Anteosaurus laticeps Boonstra, 1954 Anteosaurus levops Boonstra, 1954 Anteosaurus lotzi Boonstra, 1954 Anteosaurus major Boonstra, 1954 Anteosaurus minusculus Boonstra, 1954 Paranteosaurus primus (?) Boonstra, 1954 Pseudanteosaurus minor Boonstra, 1954 Micranteosaurus parvus Boonstra, 1954

Anteosaurus (meaning "Antaeus reptile") is an extinct genus of large carnivorous synapsid. It lived during the Capitanian epoch of the Middle Permian (266-260 million years ago) in what is now South Africa. They became extinct by the middle Late Permian.

Description

Anteosaurus had a tall, narrow skull, which is 80 centimetres (31 in) long. It was perhaps the largest known carnivorous non-mammalian synapsid, estimated at 5 to 6 m (16 to 20 ft) in length and in weight.

The teeth are another identifying characteristic of Anteosaurus. The teeth on the roof of the mouth are enlarged and confined in a cluster near the outer tooth row. The "normal teeth" include the anterior, canine and cheek teeth. A prominent feature of the dinocephalians is the ledge on the anterior teeth. The canine teeth are big, and there are usually about ten cheek teeth present. The front of the mouth curves up due to the premaxillary bone of the upper jaw.

Classification

Species

Genus synonymy

As defined by Boonstra, "a genus of anteosaurids in which the postfrontal forms a boss of variable size overhanging the dorso-posterior border of the orbit." On this basis he synonymised six of the seven genera named from the Tapinocephalus zone: Eccasaurus, Anteosaurus, Titanognathus, Dinosuchus, Micranteosaurus, and Pseudanteosaurus. Of these, he says, Dinosuchus and Titanognathus can safely be considered synonyms of Anteosaurus. Eccasaurus, with a holotype of which the cranial material consists of only few typical anteosaurid incisors, appears to be only determinable as to family. The skull fragment forming the holotype of Pseudanteosaurus can best be considered as an immature specimen of Anteosaurus. Micranteosaurus, the holotype of which contains a small snout, was previously considered a new genus on account of its small size but is better be interpreted as a young specimen of Anteosaurus. And likewise, the large number of species attributed to the genus Anteosaurus can also be considered synonyms. Boonstra still considers as valid the genus Paranteosaurus, which is defined as a genus of anteosaurids in which the postfrontal is not developed to form a boss. This is probably an example of individual variation and hence another synonym of Anteosaurus.

Species synonymy

Anteosaurus was once known by a large number of species, but the current thinking on this is that they merely represent different growth stages of the same type species, A. magnificus.

"We have 32 skulls of Anteosaurus, of which 16 are reasonably well preserved and on them ten species have been named. To differentiate between the species the following main characters have. been used: the number, size and shape of the teeth, skull size, shape and the nature of the pachyostosis. On re-examination it has become clear that the crowns of the teeth are seldom well preserved; basing the count for the dental formula on the preserved roots is unreliable. as this is affected by age and tooth generation; size of skull is a function of age and also possibly sex; sk~-shape is greatly affected by post-mortem deformation, and the variability in the pachyostosis, which may be specific in some respects, can just as well be the result of...physiological processes. Specific diagnosis consisting of the enumeration of differences of degree in features such as the above can hardly be considered as sufficient indication of the existence of discrete species....A. magnificus thus has the following synonyms: abeli, acutirostrus, crassifrons, cruentus, laticeps, levops, lotzi, major, minor, minusculus, parvus, priscus and vorsteri."
— Boonstra

Phylogeny

Below is a cladogram from a 2012 phylogenetic study of anteosaurians:

Therapsida	Biarmosuchus tener Dinocephalia Estemmenosuchus uralensis Ulemosaurus svijagensis Tapinocaninus pamelae Anteosauridae Archaeosyodon praeventor Anteosaurinae Sinophoneus yumenensis Titanophoneus adamanteus Titanophoneus potens Anteosaurus magnificus Syodontinae Pampaphoneus biccai Notosyodon gusevi Syodon biarmicum Australosyodon nyaphuli

Paleobiology

Ecology

Reconstruction of Anteosaurus showing the animal in crocodile-like posture

Olson notes that the Russian dinocephalian assemblages indicate environments tied to water, and Boonstra considered that the roughly contemporary Anteosaurus was a slinking crocodile-like semi-aquatic forms. The long tail, weak limbs, and sprawling posture do indeed suggest some sort of crocodile-like existence. This means that Anteosaurus was likely an ambush hunter waiting for its prey to come towards it before attacking with overwhelming strength and ferocity.

However the thickened skull-roof indicates that these animals were quite able to get about on land, if they were to practice the typically dinocephalian head-butting behaviour. All other head-butters (pachycephalosaurians, titanotheres, and goats) were or are completely terrestrial. Perhaps these animals spent some time in the water but were active on land during the mating season, and probably quite able to get about on land to hunt for prey.

Head-butting behavior

Anteosaurus like other related therapsids had a thickened skull (pachyostosis), and this has been suggested as an adaptation for head butting, or perhaps more aptly for head pushing. Also like with Moschops, the overall build seems to have been for projecting its body weight forwards. Not only could this have been useful in dominance head pushing contests, but it may have also been a technique to knock over unsuspecting or weakened prey.

See also

• List of synapsids

External links

• http://eprints.ru.ac.za/557/