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''Kotlassia'' (meaning "of
Kotlas Kotlas () is a types of inhabited localities in Russia, town in Arkhangelsk Oblast, Russia, located at the confluence of the Northern Dvina and Vychegda Rivers. Population: Kotlas is the third-largest town of Arkhangelsk Oblast in terms of p ...
") extinct
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
of kotlassiine seymouriamorph from the
Late Permian Late or LATE may refer to: Everyday usage * Tardy, or late, not being on time * Late (or the late) may refer to a person who is dead Music * ''Late'' (The 77s album), 2000 * Late (Alvin Batiste album), 1993 * Late!, a pseudonym used by Dave Groh ...
of
Russia Russia, or the Russian Federation, is a country spanning Eastern Europe and North Asia. It is the list of countries and dependencies by area, largest country in the world, and extends across Time in Russia, eleven time zones, sharing Borders ...
. 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 The Permian ( ) is a geologic period and stratigraphic system which spans 47 million years, from the end of the Carboniferous Period million years ago (Mya), to the beginning of the Triassic Period 251.902 Mya. It is the sixth and last period o ...
in
Northern Dvina The Northern Dvina (, ; ) is a river in northern Russia flowing through Vologda Oblast and Arkhangelsk Oblast into the Dvina Bay of the White Sea. Along with the Pechora River to the east, it drains most of Northwest Russia into the Arctic O ...
,
Arkhangelsk Oblast Arkhangelsk Oblast ( rus, Архангельская область, p=ɐrˈxanɡʲɪlʲskəjə ˈobɫəsʲtʲ) is a federal subjects of Russia, federal subject of Russia (an oblast). It includes the Arctic Ocean, Arctic archipelagos of Franz ...
, northern
European Russia European Russia is the western and most populated part of the Russia, Russian Federation. It is geographically situated in Europe, as opposed to the country's sparsely populated and vastly larger eastern part, Siberia, which is situated in Asia ...
. The locality, known as PIN 2005, consists of a creek with
sandstone Sandstone is a Clastic rock#Sedimentary clastic rocks, clastic sedimentary rock composed mainly of grain size, sand-sized (0.0625 to 2 mm) silicate mineral, silicate grains, Cementation (geology), cemented together by another mineral. Sand ...
and
lens A lens is a transmissive optical device that focuses or disperses a light beam by means of refraction. A simple lens consists of a single piece of transparent material, while a compound lens consists of several simple lenses (''elements'') ...
-shaped exposures in a
bank A bank is a financial institution that accepts Deposit account, deposits from the public and creates a demand deposit while simultaneously making loans. Lending activities can be directly performed by the bank or indirectly through capital m ...
escarpment An escarpment is a steep slope or long cliff that forms as a result of faulting or erosion and separates two relatively level areas having different elevations. Due to the similarity, the term '' scarp'' may mistakenly be incorrectly used inte ...
, containing many particularly well-preserved fossil skeletons, including the holotypes of ''
Inostrancevia ''Inostrancevia'' is an extinction, extinct genus of large carnivorous therapsids which lived during the Late Permian in what is now European Russia and Southern Africa. The first-known fossils of this gorgonopsian were discovered in the context ...
'' 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 Seymouriamorpha were a small but widespread group of limbed vertebrates (tetrapods). They have long been considered stem group, stem-amniotes (reptiliomorphs), and most paleontologists still accept this point of view, but some analyses suggest th ...
. 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 Seymouriamorpha were a small but widespread group of limbed vertebrates (tetrapods). They have long been considered stem group, stem-amniotes (reptiliomorphs), and most paleontologists still accept this point of view, but some analyses suggest th ...
.


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 ''Seymouria'' is an extinct genus of seymouriamorph from the Early Permian of North America and Europe. Although they were amphibians (in a biological sense), ''Seymouria'' were well-adapted to life on land, with many reptilian features—so ma ...
''.


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''.  The teeth of the ''Kotlassia'' are rather small, and they do not have any large tusks on the palatal bones of the skull or the lower jaw. The skull of the ''Kotlassia'' is generally short and wide, with the length of the skull being an average of 7.5 to 12.5 cm, and the width being 8.5 to 14 cm. The dermal bones which form the skull roof are similar to typical labyrinthodonts and are covered by a round-celled structure, with the round cells on some bones taking the shape of long furrows (parietal, jugal, quadratojugal, squamosal). The orbits are also quite far apart on the skull and are surrounded by 5 bones (ithe lacrimal, pre- and postfrontal, postorbital, and jugal, with the jugal being distinctly larger than the other 4), while the external naris is on the most anterior portion of the skull. There is also a large pineal opening. Additionally, the otic notch is so deep that it penetrates so far into the skull roof that there is no contact between the squamosal and tabular. The stapes of ''Kotlassia'' was a relatively small ossicle with a slightly thickened summit – which was directed towards the otic notch, assumingly united to a tympanic membrane—and wide base that is pierced by a small canal. The base of the stapes does not stay within the edges of the fenestra ovalis either, indicating that the interval between the edge of the paroccipital and stapes was covered by a cartilaginous operculum, similar to modern
salamander Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All t ...
s and
frogs A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough skin texture due to ...
.


Vertebrae and appendicular skeleton

Like ''
Seymouria ''Seymouria'' is an extinct genus of seymouriamorph from the Early Permian of North America and Europe. Although they were amphibians (in a biological sense), ''Seymouria'' were well-adapted to life on land, with many reptilian features—so ma ...
'', ''Kotlassia'' has a long dorsal transverse process, deep on the anterior vertebrae and shorter posteriously. The body of the vertebra is amphicoelus (doubly concave) and a narrow canal for the notochord can be seen in the center. Additionally, the neural arches are completely fused with the centrum, with the neural spine being weakly developed. In ''Kotlassia'', the clavicle has a large prescapular process and is strongly expanded; the external surface where the prescapular process goes off is covered with the same round cellular sculptures as the dermal bones of the skull. After passing the ventral surface of the clavicle, the round cells gradually become transformed into elongated grooves. There is also a well-developed cleithrum behind the prescapular process. As for the ilium, ischium, and pubis of ''Kotlassia'', they are completely ossified and entirely fused with each other. The tibia and femur of ''Kotlassia'' are relatively large and long, respectively, and since the metatarsal bones have not been preserved well, it is hard to accurately determine how many phalanges it had – but it has been hypothesized to be about 4.


References

{{Taxonbar, from=Q2632790 Seymouriamorpha Permian tetrapods Fossils of Russia Fossil taxa described in 1898