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Travel A road trip in Burgundy reveals far more than fine wine. Two groups of animals survived the Permian extinction: Therapsids, which were mammal-like reptiles, and the more reptilian archosaurs. In the early Triassic, it appeared that the therapsids would dominate the new era. However, by the mid-Triassic, most of the therapsids had become extinct and the more reptilian archosaurs were clearly dominant.
Archosaurs had two temporal openings in the skull and teeth that were more firmly set in the jaw than those of their therapsid contemporaries.
The terrestrial apex predators of the Triassic were the rauisuchians, an extinct group of archosaurs. In , the fossilized skeleton of a newly discovered species, Prestosuchus chiniquensis , measured more than 20 feet 6 m in length. Unlike their close relatives the crocodilians, rauisuchians had an upright stance but are differentiated from true dinosaurs by the way that the pelvis and femur were arranged. Another lineage of archosaurs evolved into true dinosaurs by the mid-Triassic.
One genus, Coelophysis , was bipedal. Although smaller than the rauisuchians, they were probably faster as they had a more flexibly jointed hip. Coelophysis also picked up speed by having lightweight hollow bones. They had long sinuous necks, sharp teeth, clawed hands and a long bony tail. Coelophysis fossils found in large numbers in New Mexico indicate the animal hunted in packs.
Some of the individuals found had remains of smaller members of the species inside the larger animals. Scientists are unclear as to whether this indicates internal gestation or possibly cannibalistic behavior. By the late Triassic, a third group of archosaurs had branched into the first pterosaurs. Sharovipteryx was a glider about the size of a modern crow with wing membranes attached to long hind legs. Palaeontologists believe placerias ate low-growing plants, as well as using its tusks and beak to grub for roots and tubers.
The dicynodonts were very successful before they died out. One of the first true dinosaurs was coelophysis "hollow form" , a carnivorous, bipedal predator that emerged in the late Triassic, between and MYA.
Hollow-boned coelophysis grew up to 3 metres in length, weighed around 27kg and probably fed on smaller reptiles and amphibians. It had curved claws on its hands and a slim head crammed full of very sharp teeth. Some experts have suggested that coelophysis could bring down bigger animals by taking slashing bites out of their legs or sides.
Fossil coelophysis skeletons have been found in the same locations, so it's possible that these dinosaurs may have herded, although there's no firm evidence that they hunted in packs.
It is also believed that coelophysis was a cannibal that preyed upon its own young during lean times. Around MYA, a new type of dinosaur emerged - the giant herbivore, plateosaurus "flat lizard". Weighing around 3 tonnes and growing up to 7 metres, plateosarus was a forerunner of the huge Jurassic dinosaurs.
It had a long, powerful tail and a set of coarsely serrated teeth for chewing tough vegetation. We're not sure whether this was used for food collection or defence. Large numbers of plateosaurus skeletons have been found in the same location, suggesting they may have herded.
Alternatively, instinct drew them to the same place to die.
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