Named by: Watson, 1921
Taxonomy: Synapsida, Eupelycosauria, Sphenacomorpha, Sphenacodontia, Sphenacodontoidea, Therapsida, Dinocephalia, Anteosauria, Anteosauridae, Anteosaurinae
Included Species: †A. magnificus (type), †A. rugosus?
Anteosaurus is a genus of large carnivorous therapsids, which lived in what is now South Africa roughly 260 to 265 million years ago. With a length of six meters (20 feet) and mass of 600 kilograms, they were the first truly gigantic terrestrial predators and among the largest predatory synapsids to have ever walked on land; their size is comparable to that of polar bears and mid-sized predatory dinosaurs such as Dilophosaurus and Megalosaurus. The largest known skulls of Anteosaurus are over 80 cm (32 in) long, only slightly smaller than the 83-cm skull of Andrewsarchus, the largest carnivorous terrestrial mammal known to have ever lived.
Anteosaurus lived in an upland environment, where they were among the most abundant predators, and hunted large prey such as dicynodonts and herbivorous dinocephalians. Due to their large size and short limbs, Anteosaurus were unlikely to have been particularly fast by modern standards. However, they didn’t need to be. Specialized cursorial animals had yet to evolve, and Anteosaurus lived in an environment rich in large, slow herbivores. Being able to tackle their prey was more important than being able to chase it, and Anteosaurus were certainly more than capable of outrunning and bringing down the large herbivores of their time. Furthermore, as the largest and most powerfully-built predators in their ecosystem, Anteosaurus could have also easily driven off smaller predators, such as the early gorgonopsian Eriphostoma and the therocephalians Glanosuchus and Pristerognathus, in order to steal their kills.
As was common in early therapsid predators, Anteosaurus had large incisors and canines, but only small teeth behind the canines. The incisors interlocked for a precise, flesh-shearing bite. Unusually, the small postcanine teeth were robust and somewhat turned out to the side, and may have been used for crushing bone.
Like other dinocephalians, Anteosaurus were characterized by cranial pachyostosis, or thickening of the skull bones. Anteosaurus had the greatest cranial pachyostosis of any predatory dinocephalian genus and bore thick forehead domes and bosses over their eyes, on their cheeks, and on their lower jaws. Such robust, knobby skulls are not uncommon among large predators, such as tyrannosaurids, and would have provided reinforcement for powerful, bone-crushing bites. It is possible that these adaptations were also involved in display and intraspecific combat, with rival Anteosaurus participating in shoving matches and trying to bite each other with their powerful canine teeth. Similar behavior has been recorded in modern hogs.
It is possible that a second species, Anteosaurus rugosus, lived in Russia, but the known remains are too incomplete to conclusively prove that they belong to Anteosaurus rather than its slightly smaller Russian relative Titanophoneus. A. rugosus lived alongside Titanophoneus and a much smaller anteosaur, Syodon.
Anteosaurus went extinct, along with the rest of the dinocephalians, approximately 260 million years ago. This extinction event is likely to be the result of volcanic activity in what is now China leading to darkened skies and less plant growth, thus collapsing the food chain Anteosaurus relied upon.
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