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Dicynodonts

Dicynodonts—“Two fangs” are the representatives of Theromorpha—large mammal-like reptiles group. In their structure they had many progressive features. That’s why they differed from reptiles already in Upper Permian. It’s else one species of planteating animals, found on Kotelnich locality. First time the remains of lower jaw and a part of dicynodont’s skull were found in 1991. In 1992 the large accumulation of dicynodonts’ bones were found near Kotelnich. Within the town, not far from the River Port there was found a level containing numerous remains of dicynodonts. This level stretched for 350 meters within the foundation of the right river-side. During recent years some complete skeletons and a large collection of dicynodonts skulls, a plenty of separate bones were found on this place. All finds are found in one level. Their concentration is very high. It says about their mass synchronous death on this territory.

reconstruction Dicynodonts

Dicynodonts lived more than other Permian reptiles: having come in Upper Permian they lived up to the end of Middle Triassic, constantly altering. Dicynodonts had some evolutional transformations. The latest representatives of this mammal-like reptiles group had highly imposing sizes, for example, Triassic dicynodonts Shtolikeria could be higher than a modern elephant. Besides that, dicynodonts settled on all continents. Their remains are found even in Antarctic Continent. Especially numerous finds of dicynodonts are in the South Africa and China. Many finds were in East Europe. Near Kotelnich to all appearances it was found the largest locality of dicynodonts remains in Europe.

Studying of Kotelnich finds are not finished yet and on this moment there is no scientific description, it is only made. Probably, dicynodonts from Kotelnich could be attributed to South Africa’s genus Tropidostoma and were transition stage between little lizard, like Dromosaurus and Dicynodonts. It means they were a link group inside anomodontia (“lizards with abnormal teeth”), to which belong both Dromosaurus and Dicynodonts.

Dicynodonts

It was already pointed that Dicynodonts were planteating, gregarious, lived near water. There is quite grounded supposion that some of them, especially later Dicynodonts had hair covering skin, could have more or less constantly body temperature and viviparous. If it was in reality difficult to judge. The fine preservation of Kotelnich Dicynodonts let the investigators to study the structure of early Dicynodonts more carefully. Perhaps it makes clear many questions of biology of these strange animals.

In spite of mass Dicynodonts finds there are not so many complete skeletons, less finds of fine preservation. On the Karoo Basin of South Africa they find up to 10 skulls of Triassic Dicynodonts Lystrosaurus on one square meter. The finds of skeletons are very rare. Almost all material is bad safety and can’t be studied in details.

reconstruction Dicynodonts

The skull has unusual proportions: good developed malar arcs (jugale) curving out, the skull with high vault has bone comb, between its branches there is pineal foramen—“the third eye”. Such bones modification served for fastening of powerful bundles of masticatory muscular system. Because this reason the cranium gets narrow. It leads to deereasing of small brains. The jaws of animals are transformed into the beak (bill?). They are similar to tortoise's jaws. On upper jaw (maxillare) in fang bags (alveols) there are 2 powerful fangs. They are round in section and probably they served as digging implements, helping the animals search for plant roots (like wild boars). The fangs are good pronounced and begin some skulls which totally absent from others. This has bad to the theory of sexual dichotomy among Dicynodonts. In generally Dicynodonts had an evolution tendency to loss their teeth and fangs completely. Later representatives of this group had no fangs at all. Behind fangs on upper jaw bones Kotelnich Dicynodonts have a primitive sign—small teeth crowns. Their form has remote likeness with pareiasaurs’ teeth.

First of all, just this reason is very important for scientists, because it lets to retrace the chain of evolutional transformation from little lizard like Dromosaurs, their representative on Kotelnich locality is Suminia getmanovi, to proper Dicynodonts—planteating lizards with 2 strange fands. On their way to planteating they lost the teeth system and transformed the skull in a device used only for eating plants. It’s a tribute to specialization, which every living organism pays.

Grazing on boundless riverside plains of Permian and Triassic Dicynodonts picked leaves and young plants with their powerful jaws, covered with strong horny beak, cut food with sharp jaw edges, after that food went into the digestive canal.

The layer with Dicynodonts’ remains is an original locality, isolated from main locality of Pareiasaurs fauna. It is bedding in bank uncovering upper that Pareiasaurs level. It is evidence that Dicynodonts lived here later. At the same time the temporary space between these two palaeofaunas hardly took a long time.

 

Suminia getmanovi

 

Suminia getmanovi

In 1990 near Boroviki village, situated in 18 km. from Kotelnich down stream, first practically complete skeleton of small lizardlike animal was found by S. N. Getmanov, a collaborator from the P.I.N. of the USSR. As it later turned out it was planteating dromosaur (it means “running” or “mobile” lizards), the representative of bad studied group of Permian lizards. The find was described by M. F. Ivachnenko, a doctor of biology from the P.I.N. of the Russia, and was called Suminia getmanovi in honour of D. L. Sumin, who headed this job and in honour of S. N. Getmanov, who was the author of the find.

Suminia getmanovi

It was the first find of practically completely Dromosaur’s skeleton, moreover it was in a very good state preservation. Some skeletons of Suminia and than 10 separated skulls of these animal were found on the locality during next years.

The skeleton of Suminia is quite gracile: long limbs with thin strong fingers. Probably in lifetime they joined by swimming web. Every finger finishes with sides flattened out turning down claw. The neck of the animal is disproportionate length, it has a small delicate skull. The belly of Suminia was completely reinforced with very thin belly ribs. Probably there was quite long tail with massive base.

Suminia getmanovi

A special interest is the skull of Suminia. A complex of some signs united Suminia with Dicynodonts’ ancestors: large temporal windows, the appearing of bone comb, decreasing of brain box size, beginning of turning malar bones out and some others features of structure. Jaws have a row of powerfull similar teeth, adapting for biting off and crushing wood of young horse-tails-like plants. By detail microscopic research of teeth crowns numerous tracks were noticed. There are the abrasion marks, made by little silicate crystals, containing in horse-tails in plenty. So with most of probility it succeeded to determine the food type, which Suminias prefered 255 millions of years ago.

Suminia getmanovi