Anteosaurus

Anteosaurus Temporal range: Capitanian, 266–260 Ma PreꞒ Ꞓ O S D C P T J K Pg N
A. magnificus skull, Iziko Museum
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Clade:	Synapsida
Clade:	Therapsida
Suborder:	†Dinocephalia
Family:	†Anteosauridae
Subfamily:	†Anteosaurinae
Clade:	†Anteosaurini
Genus:	†Anteosaurus Watson, 1921
Species:	†A. magnificus
Binomial name
†Anteosaurus magnificus Watson, 1921
Synonyms[1]
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 synapsids. It lived during the Capitanian age of the Guadalupian epoch (266–260 million years ago) in what is now South Africa. Like the well-known Moschops, they were dinocephalians, a clade of large-bodied therapsids that flourished from 270 to 260 million years ago and then went extinct without descendants.

Paleontologists once surmised that Anteosaurus hunted rather like crocodiles, pulling land animals into the water. In particular, scientists pointed to the animal's strong tail and supposedly weak, sprawling legs as proof of this lifestyle, but in 2021 new examinations of its brain suggest it was largely terrestrial, with highly advanced senses of vision, balance and coordination. It was also very fast and would have been able to outrun competitors and prey alike thanks to its advanced adaptations.^[2] Its body was well-suited to projecting itself forward, both in hunting and evidently in head-butting.

Description[]

A. magnificus restoration

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 5–6 m (16–20 ft) in length and 500 to 600 kg (1,100 to 1,300 lb) in weight.^[3][4]

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 Lieuwe Dirk Boonstra, Anteosaurus is “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.^[4][5][6]

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.^{[citation needed]}

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^[4][5][6]

Possible synonyms[]

Archaeosuchus[]

Archaeosuchus cairncrossi is a dubious species of anteosaur from the Tapinocephalus Assemblage Zone. It was named by Broom in 1905 on the basis of a partial maxilla. It was interpreted as a titanosuchid by Boonstra, but Kammerer determined it was an anteosaur indistinguishable from Anteosaurus and Titanophoneus. As Anteosaurus magnificus appears to be the only valid large anteosaur in the Tapinocephalus Assemblage Zone, Archaeosaurus cairncrossi is very likely to be based on a specimen of it, but due to poor preservation, the specimen lacks any features that would allow the synonymy to be proven.^[1]

Eccasaurus[]

Eccasaurus priscus is a dubious species of anteosaur from the Tapinocephalus Assemblage Zone. It was named by Robert Broom in 1909 on the basis of a fragmentary skeleton, of which Broom only described the humerus. As with Archaeosuchus cairncrossi, Eccasaurus priscus is very likely to be synonymous with Anteosaurus magnificus. As Eccasaurus was named before Anteosaurus, a petition to the ICZN would be needed to preserve the name Anteosaurus magnificus if the synonymy were to be proven.^[1]

Phylogeny[]

Below is a cladogram from a 2012 phylogenetic study of anteosaurians:^[7]

Paleobiology[]

Ecology[]

Reconstruction of Anteosaurus showing the animal in a crocodile-like posture

Olson notes that the Russian dinocephalian assemblages indicate environments tied to water, and Boonstra considered that the roughly contemporary Anteosaurus were slinking crocodile-like semi-aquatic forms. The long tail, weak limbs, and sprawling posture were once thought to have suggested some sort of crocodile-like existence.^[4]

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.^[4]

An in-depth study of the brain of Anteosaurus published in 2021 disproves the idea that this dinocephalian was a sluggish, crocodilian-like predator. Studies by Benoit et al. using x-ray imaging and 3-D reconstructions showcase that Anteosaurus was a fast, agile animal in spite of its great size. Its inner ears were larger than those of its closest relatives and competitors, showcasing that it was well-suited to the role of an apex predator that could outrun both its rivals and prey alike. It was also determined that the area of the brain of Anteosaurus that was responsible for coordinating the movements of the eyes with the head was exceptionally large; an important feature in ensuring it could track its prey accurately. As a result, Anteosaurus was well-adapted to swift hunting and fast attacking strikes.^[2]

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. Palaeoneurological analysis of the skull of A. magnificus has shown, however, that the degree of pachyostosis in its skull was significantly lower than in Moschops; instead, Anteosaurus would most likely have made use of its large canines as a weapon in intraspecific fights.^[2]

See also[]

• List of therapsids

References[]

External links[]

• https://web.archive.org/web/20110718172130/http://eprints.ru.ac.za/557/
• https://www.wits.ac.za/news/latest-news/research-news/2021/2021-03/prehistoric-killing-machine-exposed.html