Garjainia triplicostata Archosauria: Thecodontia: Proterosuchia: Erytroshuchidae Locality: Rassypnaya, Orenburg Region, eastern European Russia Age: Early Triassic, 240 million years ago Meaning of name: named after Dr. V. Garjainov, Russian geologist Size of a lion From the end of the Permian, large Paleozoic terrestrial predators conceded their place to thecodonts. This was the premiere of the archosaurians, a very diverse and numerous group which occupied a supreme position among terrestrial tetrapods during the entire Mesozoic. The exhibition presents a skull reconstruction of the most ancient known thecodont of the Late Permian genus Archosaurus. Thecodonts probably originated in some relatively high and dry environments and were specialized to feed on scaled reptiles. There were no fangs in thecodonts, their sharp teeth almost uniform in shape and size. These teeth formed a saw adapted to cut rigid but not too thick skin. However when thecodonts came to occupy coastal lowlands, they had to change their prey, which caused modification in the structure of their jaw and teeth. In order to hunt for animals with a relatively soft thick skin, such as dicynodonts, the thecodont jaws stretched forward and curved down, while anterior teeth lengthened to help in tearing the flesh of the victim. Agile thecodonts were dangerous for sluggish and clumsy dicynodonts. The main protection of the last was a general increase in size, and by the late Early Triassic some dicynodonts got as large as modern rhinoceroses. But the increase in size in hervivorous animals is always accompanied by a parallel increase in size of the predators hunting for them. Therefore simultaneously with large dicynodonts, very large flesh-eating thecodonts existed, for example, of the genus Garjainia. Garjainia was a very primitive member of the Thecodontia, whose name derives from the fact that the teeth are rooted in deep sockets. Thecodonts gave rise to most groups of later reptiles, the archosaurs, and they took over from the ruling mammal-like reptiles, the therapsids. Garjainia was a confirmed carnivore, and its similarity to some of the highly specialized carnivorous mammal-like reptiles is striking. By the end of the Triassic period, the mammal-like reptiles had been driven close to extinction and the world was overtaken by the 'offspring' of thecodonts, including the dinosaurs, which prospered over the next 140 million years. |
