Kotlassia (meaning "of Kotlas") extinct genus of kotlassiine seymouriamorph from the Late Permian of Russia. The type, and currently only, species is K. prima.
Discovery and naming
During the 1890s, Russian paleontologist Vladimir Amalitsky discovered freshwater sediments dating from the Upper Permian in Northern Dvina, Arkhangelsk Oblast, northern European Russia. The locality, known as PIN 2005, consists of a creek with sandstone and lens-shaped exposures in a bank escarpment, containing many particularly well-preserved fossil skeletons, including the holotypes of Inostrancevia and Kotlassia.
Vladimir Amalitzky named and described Kotlassia prima in 1921 on the basis of the holotype specimen, an entire skeleton, and one additional skull; the additional skull has been described ad over-prepared by Bulanov (2003). It is often incorrectly assumed that Kotlassia prima was described by Amalitzky in 1898.
A second species, K. secunda, was also named by Amalitsky (1921), but it has since been placed within the genus Karpinskiosaurus as K. secundus.
In 1935, Aleksandra Paulinovna Anna Hartmann-Weinberg falsely identified several ribs and osteoderms she found in Amalitsky’s collection, to Kotlassia prima. Later, these would actually be confirmed to be the first chroniosuchian remains. However, because of Hartmann-Weinberg’s false attribution previously attributing the ribs and osteoderms to Kotlassia, subsequent osteoderms and vertebral columns discovered later – originally belonging to chroniosuchids – would be ascribed to Kotlassia, before the corrections would be made.
Classification
Kotlassia has been allied with the family Kotlassiidae, which is within the order Seymouriamorpha. It has been highly debated where exactly the Kotlassia falls into, within a phylogenetic tree, but recent analyses have chosen Kotlassia to be a basal member of Seymouriamorpha.
Description
Kotlassia grew up to around in length, and possessed many amphibian-like characteristics.
Similar to other reptiles, Kotlassia had 2 sacral vertebrae present, however their limbs were generally smaller with a more ‘salamander-like frame’, which was indicated by its longer torso and shorter legs, hinting towards an aquatic lifestyle.
Also, the skull of Kotlassia was small, possessing a shorter rostrum, slender stapes, and more dorsally directed orbits. Additionally, while the adult form was terrestrial, it has been hypothesized that the Kotlassia had an aquatic larval stage, similar to Discosauriscus and Seymouria.
Skull
Many seymouriamorphs had sharp, slightly curved, conical teeth and palatal fangs, suggestive of a predatory lifestyle. They also had labyrinthine marginal teeth, with Kotlassia having a small row of labyrinthine teeth on the palatine and transverse bones, forming an S-shaped row on each side. The tooth size decreases gradually from the internal naris farther away. Delving into their tooth structure, Kotlassia had the same kind of folds in the dentinal walls of their teeth as the typical labyrinthodont – such as Benthosuchus sushkini. Both Kotlassia and Benthosuchus had the same number of folds, and it is assumed that due to their vastly similar tooth structures that Kotlassia had the same order of change of their teeth as B. sushkini.