Therocephalians - Mammal-Like Reptiles
Therocephalians (Greek: Therion-animal+kephale-head) - are more progressive group of predator Therapsids-Theriodonts, they appeared in Upper Permian of Russia and South Africa. Up to now their origin is unknown. Their ancestors could be primitive predator Therapsids. Therocephalians were more various than Gorgonopsians, included small, perhaps, insectivorous Scaloposauridaes, big predators Pristerognathidaes and planteating Bauriidae.
Therocephalians are characterized by massive, little consolidate skull, simple conic behind fangs teeth, some of their representatives have the second palate. Some representatives of this group with their body proportions were similar to mammals. Few finds of skeletons’ remains point on this fact. In Kotelnich fauna Therocephalians reached large variety and quantity. It is one of the few palaeofaunas where were found not only completely skulls of some species of Therocephalians in a very good state of preservation, but also fragments of skeletons of these animals valuable in evolutional attitude.
The first Therocephalian, described from Kotelnich fauna, is Viatkosuchus sumini-(“Viatka crocodile”). Its completely skull and the front part of skeleton were found in 1991. During burial process the skeleton suffored from cracking very much, before getting in sediment the remains of skeleton was on the surface for a long time. That’s why the bones are in a very bad state of preservation. But it is a very front limbs of Viatkosuchus were short and strong and stood apart at an angle of 90 degrees. It points that the animal hardly was mobile like a predator mammal, by attack on the prey, which were little planteating animals Suminias and lizard-like Ripeosaurs, the animal used an ambush tactics of hunt. Up to now Viatkosuchus is the biggest Therocephalian from Kotelnich redbeds.
The second was found and described small, probably, insectivorous Scaloposaurian Karenites ornamentatus. Its genus name is formed from the name of Karen E. Bogachev, the leader of the commercial firm “Stone Flower Company”, made works on the locality in 1990-1994. From Karenites we know a skull without snout tip and the front part of skeleton, which is very carbonating. In a state of a very good preservation the skull, prepared with help of weak acid solution, shows all structure details and it is an example of unique preservation of fossil material in red clay rocks (madstone) of Upper Permian, spread very wide on the territory of European part of Russia. Academician L. P. Tatarinov, having studied this find, thinks, that Karenites had a large well developed cerebrum. This fact tells them from all permian reptiles very much and in complex with other progressive signs brings together first mammals ancestors.
Graddually, the number of Scaloposaurus finds grows up. Later L. P. Tatarinov described Scalopodontes kotelnichi; Perplexisaurus foveatus; Scalopodon tenuisfrons; Chlynovia serridentatus...
But in spite of many progressive signs, which unite Therocephalians with mammals, only Cynodonts (“dogs’ teethed”) came near to their structure. But forming of proper mammals used millions years of evolution else up to the Cynodonts’ remains, the most progressive group of beast-like reptiles are not found on Kotelnich locality. The plenty of Therocephalians’ finds and their very good preservation let to study in details the forming way of a new class of vertebrates--mammals between Palaeozoic and Mesozoic Eras.