Saturday, 2 January 2010

Anteosaurs; Gorgonopsids on steroids!

Above; Dmitry Bogdanovs reconstruction of Anteosaurus shows it as a short tailed beast with a distinctively hyena like appearence.

Anteosaurs belonged to a group of Protomammals known as Dinocephalians. These animals were much more primitive than the Gorgonopsids and were the dominant animals in the mid Permian period about 260 million years ago. There were carnivorous, omnivorous and herbivorous Dinocephalians. The carnivorous forms; called Anteosaurs died out before the end of the Permian as the Gorgonopsids and Therocephalians took over.

These gigantic animals got much bigger than the Gorgons, some possibly reaching lengths of up to 6 meters! Anteosaurs were also much more heavily built, with short skulls and broad teeth.

Above; with a head 80cm long Anteosaurus would have been yay big compared with a man between 5 and 6 feet tall.

The incisors occlude to form a strong gripping surface. The palate also possesses teeth and behind the canines are molars. This dental armoury is very different from the Gorgonopsids, which lost all teeth behind the canines very early in their evolution. Gorgonopsids simply bolted down flesh as quickly as possible, processing it in the gut. The teeth of Anetosaurs show that they probably chewed their food to some degree, possessing a strong SP (static pressure) component in the bite. That is to say that these animals applied a large amount of force when the jaws were nearly closed, giving Anteosaurs a strong grip.

Above; the bite of Titanophoneus.

The large size did cause problems for the Anteosaurs. For starters they still had lizard like bodies, unlike the more slender Gorgonopsids. Because of the weak sprawling legs it has been suggested that these animals were aquatic, however the tail is rather thin and useless for swimming. Perhaps these animals were active hunters as juveniles and as they got older, heavier and slower they may have resorted to scavenging as the strong teeth suggest. Another possibility is that they did not need to be fast. The prey of the Anteosaurs merely consisted of herbivorous Dinocephalians and Pareiasaurs, both groups were large and slow moving anyway.
Above; the large and cumbersome herbivorous Dinocephalians were easy prey for the equally clumsy Anteosaurs.

When you look at the skeleton of Titanophoneus; a large Anteosaur from the mid Permian of Russia the legs do not look all that weak, certainly big enough to support it on land. The body is relatively short, not long and tubular like that of a lizard, perhaps to retain core body heat.

Above; the skeleton of Titanophoneus showing features such as a thin tail and compact bodyto contain heat.

Another feature not yet covered in detail is the skull shape itself. When the skull of Anteosaurus from South Africa is observed its broadness becomes apparent. This animal was way more heavily built than Titanophoneus, designed to tackle much larger prey. The height of the temporal fenestra (temple) suggests a large area for the temporalis jaw muscle. This muscle was at a right angle to the lower jaw when it was nearly closed, utilizing all of the closing power towards the end of the bite and giving it a firm grip. The canines of all Anteosaurs are curved backwards like hooks. This is unlike the tearing canines of the Gorgonopsids or the stabbing canines of the Therocephalians. These were hooks designed to catch the preys hide in its vice like jaws.
Above; the skull of Anteosaurus was heavily built. The eyes are on top of the head, leading some scientists to suggest that these animals were semi aquatic.

The hunting strategy was therefore unique for mammal like reptiles. These slow moving Anteosaurs probably ambushed their prey at close range, lunjing at the weakest individual and clamping an arm or leg firmly in its jaws. The hook like canines and crushing teeth would injure a large herbivore beyond recovery. If these animals were social they may have hunted in packs. Whilst one grabbed a limb to keep the prey restrained another may have grabbed the neck, crushing the whindpipe and suffocating the prey. To do this strong jaws were needed to grip the neck untill the prey died and if this is the case then Anteosaurs hunted very much like lions do today.
Above; Robert Bakkers reconstruction of Anteosaurus shows it attacking the herbivorous Dinocephalian Keratocephalus. The body of Anteosaurus has been reconstructed with a much longer tail and shorter legs than that of Dmitry Bogdanov, giving it an appearence more akin to Titanophoneus.

Alternatively the strong jaws could have been used to pull the victim into the water, drowning it.

The skulls of all Dinocephalians including Anteosaurs were thickened towards the roof. This suggests possible head butting behaviour like modern sheep. The orbits of Anteosaurus are raised and arch like to help withstand the blow of a head butt.

Generally the Anteosaurs were more primitive relatives of the Gorgonopsids, uncles you may say. Whereas the Therocephalians are more like brothers or sisters. By the late Permian a group of herbivorous Dinocephalians became smaller and faster. These were the Anomodonts, tiny to medium sized burrowing reptiles that soon usurped the large herbivores as dominant plant eaters. This may have been due to the drying out of the landscape and the growth of desert environments towards the end of the Permian which resulted in less food and therefore the large herbivorous Dinocephalians were unable to support their own bulk with enough food and died out. With less large herbivores the Anteosaurs also became extinct, too big and ungainly to hunt the Anomodonts that were swiftly taking over. These Anomodonts became so abundant that an entire deposit of rocks has been named after just one genus that is found commonly fossilized in this sequence; the Cistecephalus zone.

Above; the abundant burrowing Anomodont Cistecephalus from the late Permian of South Africa took over from its earlier Dinocephalian contemporary Tapinocephalus to become dominant herbivore.

The more slender Gorgonopsids took over the role of top predator. With their longer legs and smaller size (the average Gorgon being only a meter or so long) they were able to survive on the smaller herbivores.

Some however became large (Inostrancevia) due to the remaining presence of Pareiasaurs, huge 3 meter turtle relatives. These animals were cold blooded as opposed to the possibly warm blooded herbivorous Dinocephalians and therefore thrived in a dry hot environment. Some Gorgons therefore got larger to take advantage of this food source.

Above; some Gorgonopsids like Inostrancevia from Russia got bigger due to the prescence of large Pareiasaurs. The image shows Gorgons with a coat of fur which emphasizes our changing view about Gorgonopsids.

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