The Mesozoic Era is often known as the Age of Reptiles. 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. One genus, Lystrosaurus, has been called the Permian/Triassic “Noah,” as fossils of this animal predate the mass extinction but are also commonly found in early Triassic strata. 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 2010, the fossilized skeleton of a newly discovered species, Prestosuchus chiniquensis, measured more than 20 feet (6 meters) 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. It was obviously bipedal with tiny, clawed front limbs that were probably used to grasp prey as it jumped and glided from tree to tree. Another flying reptile, Icarosaurus, was much smaller, only the size of a hummingbird, with wing membranes sprouting from modified ribs.
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 2010, the fossilized skeleton of a newly discovered species, Prestosuchus chiniquensis, measured more than 20 feet (6 meters) 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. It was obviously bipedal with tiny, clawed front limbs that were probably used to grasp prey as it jumped and glided from tree to tree. Another flying reptile, Icarosaurus, was much smaller, only the size of a hummingbird, with wing membranes sprouting from modified ribs.
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