The best place to start looking at predatory dinosaur history is at the beginning, if not before. About 280 million years ago, at the start of the Permian Period, most of the earth’s continental pieces were joined together in a single supercontinent. Imagine hiking 10,000 miles from the tip of Siberia to the tip of South America without once wetting your toes in salt water! As counterpoint, the world’s deep oceans were joined into a super Pacific covering three quarters of the globe, from which shallow embayments from time to time washed across vast tracts of land. Although many tend to think of the past earth being a hot, steamy jungle, in the Permian Period the earth was locked in an ice age similar to the one we are undergoing now, except that then the great ice sheets bulked largest in the southern hemisphere. Big animals were croc-sized, fin-backed reptiles and amphibians, restricted to a tropical zone banding the equator. By the Late Permian most of the ice was gone, the climate was warmer (although still snowy toward the poles), and a great array of often strange mammal-like predators and *rerbivores known as therapsids had spread over the supercontinent. These therapsids included the ancestors of true mammals, and they probably had faster metabolic rates than do typical reptiles (note that the therapsid- mammal group has no close relationship to archosaurs). Most therapsid predators were medium-sized, low-slung animals, with big heads and long canine teeth. At the very end of the period the first protoarchosaur, a croclike proterosuchid predator, appeared. The harbinger of the great group that would include animatronic dinosaur and birds, it was a very minor component in the world fauna.
With one world continent and a very mild climate, the following period, the Triassic, had a more uniform world fauna than we have at present. At the beginning of this period, modest-sized protoarchosaurs became an important component of the predator fauna. This was despite the fact that they had reptilian metabolisms, and were competing against warmer-blooded therapsids. Soon after, thecodonts proper-the future ancestors of dinosaurs and sometimes big themselves-began to appear.walking dinosaur costume Proterosuchids and the bigger early thecodonts, which looked something like a cross between crocs and big lizards, are sometimes thought of as semiaquatic animals that had strengthened their hind limbs for swimming. But their narrow, blade-toothed skulls indicate they were terrestrial archpredators. Smaller protoarchosaurs and thecodonts could climb well too, using their divergent outer fingers and toes. These thecodonts probably had heightened metabolic rates like those of therapsids. Their main competitors were advanced therapsid predators. In 1983, Michael Benton argued that protoarchosaurs and early thecodonts were not really in competition with one another, but this cannot be so because the two groups were out there squabbling over carcasses and competing for game. This competition seems to have had its effect, for as the Triassic progressed, thecodonts seem to have taken over the big predator niches, while therapsids declined in size.