The major group of reptiles in the Permian period were those that we call the mammal-like reptiles. This was a group of synapsid reptiles that evolved more and more mammal-type features as they developed, and eventually evolved into the mammals themselves. The earliest forms were not particularly mammal-like but showed some of the early features that define the group. walking dinosaur costume
Ophiacodon was quite a large animal and may have spent much of its time in or near the water, where it would have hunted amphibians or fish, as well as on land where it would have preyed upon more terrestrial reptiles. There were several species, appearing at slightly different times. The teeth in the long jaws resemble those of the big fish-eating amphibians more than those of the later repriles. This is one of the reasons for rhe suggestion that Ophiacodon was a semi-aquatic fish-hunter.
Features The skull is quite deep and narrow, giving a good attachment area for strong jaw muscles, suggesting a powerful bite. Unlike the earlier pelycosaurs that are sprawling and lizard-like, the hind legs of Ophiacodon were held more directly beneath the body, indicating an ability to run down its prey. The forequarters are strong, presumably to hold up the big head. The teeth are quite small and beginning to show a differentiation in size.
Below: Some scientists disagree with the proposed aquatic lifestyle of Ophiacodon, thinking the tall narrow skull would make this impractical.
The diapsids as a group are characterized by two holes in the side of the skull behind the eyes. These held the muscles that worked the jaws.
At first they were small lizard-like animals, but soon they evolved into all sorts of specialized shapes – fliers, swimmers and burrowers. The main ecological niches for big animals, were at this time taken by the parareptiles and the mammal-like reptiles, and so the diapsids remained small and insignificant. realistic dinosaur model
It is almost the same situation as that of the mammals during the Age of Dinosaurs – quite diverse but small and insignificant. It took the extinction of the dinosaurs to allow the mammals to develop into what they now are.
Likewise, it was the mass-extinction of the parareptiles and the bulk of the mammaMike reptiles at the end of the Permian that allowed the diapsids to develop. They would become the crocodiles, lizards, snakes, and even the great swimming reptiles of the Mesozoic as well as the dinosaurs and birds.