#araeoscelis

[alphynix]

Araeoscelis gracilis was a superficially lizard-like animal that lived during the mid-Permian, around 275 million years ago, in what is now Texas, USA. About 60cm long (~2'), it had a slender body, proportionally long legs, and a solidly-built skull with strong teeth, suggesting that it was a fast runner that specialized in cracking open the carapaces of thick-shelled prey.

It was one of the last known members of a lineage known as araeoscelidians, which are usually considered to be very early members of the diapsid reptiles – but a recent study has proposed they might have even more ancient roots than that, possibly being a branch of stem-amniotes instead.

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[antiqueanimals]

Predatory Dinosaurs of the World: A Complete Illustrated Guide. Written and drawn by Gregory Paul. 1989.

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[neovenatorgirlteeth]

DINOVEMBER DAY 6: 275MYA, KUNGURIAN STAGE; TEXAS, USA

(I'm going to try to catch up and get day 6, 7 & 8 up tonight. Wish me luck. Once again I recommend the Walking With Monsters OST, this time, the track Fight Over The Nest)

The hyper-oxygenated atmosphere of the Carboniferous became unstable, with extreme weather and untameable fires, bolstered by the high oxygen levels, that tore through the forests. The end Carboniferous rainforest collapse, which occurred 305MYA, was caused by these factors as well as volcanic activity in Scandinavia, and has fragmented the coal forests into isolated ecological islands. This has brought an end to the reign of the giant arthropods on land, and the amphibians have suffered as well, but in the end this was not a severe enough event to class as a mass extinction. There has, however, been a shift in power and in the place of the amphibians, the amniotes, their sister group, has risen up. Whereas the amphibians dominated the swampy lowlands, the amniotes cut ties with the water and took up residence in the drier uplands. They have many adaptations to do this, but most significant of these are their scaly skin which does not lose water in the way soft amphibian skin does, and the fact that their eggs now have shells which mean that they can be laid on land.

From the very beginning, the amniotes split into two groups; the synapsids and the sauropsids. Back in the Carboniferous, they were only separated by the number of holes that make their skulls lighter, but the groups quickly diverged. Now, in the early Permian, synapsids rule, and the sauropsid are crushed underfoot: quite literally for one unfortunate Araeoscelis. On top of it is the apex predator of the seasonal marshes of Northern Texas; the sailbacked Dimetrodon. She is the very picture of synapsid success, almost 5m long and 2m tall with her impressive sail. She likely uses this sail to warm up in the morning sun in order to get the edge on her prey, though some prey animals like the closely related Edaphosaurus have equally impressive sails of their own. She may also use it for display, helping her attract mates or scare off rivals.

Although her sail is impressive, it does not make her deadly. What does is her teeth, recurved and serrated for ripping into flesh, and her stance, holding her body slightly off the ground. It is more comparable to the high walk of a crocodile than it is to the fully upright stance of a mammal or dinosaur, but it gives her the speed advantage over prey who might still be scraping their bellies on the ground. Large, vicious and fast moving, Dimetrodon is the shape of things to come. This is the Permain, the age of the Synapsids.