''Rautiania'' is an

extinct Extinction is the termination of a kind of organism or of a group of kinds (taxon), usually a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and ...

genus Genus ( plural genera ) is a taxonomic rank used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In the hierarchy of biological classification, genus com ...

of gliding

neodiapsid Neodiapsida is a clade, or major branch, of the reptilian family tree, typically defined as including all diapsids apart from some early primitive types known as the araeoscelidians. Modern reptiles and birds belong to the neodiapsid subclade Sau ...

reptile Reptiles, as most commonly defined are the animals in the class Reptilia ( ), a paraphyletic grouping comprising all sauropsids except birds. Living reptiles comprise turtles, crocodilians, squamates (lizards and snakes) and rhynchocephalians ( ...

s belonging to the family

Weigeltisauridae Weigeltisauridae is a family of gliding neodiapsid reptiles that lived during the Late Permian, between 258 and 252 million years ago. Fossils of weigeltisaurids have been found in Madagascar, Germany, Great Britain, and Russia. A possible weigelt ...

. Isolated fossil remains of ''Rautiania'' are known from the Late

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 251.9 Mya. It is the last period of the Paleoz ...

Russia Russia (, , ), or the Russian Federation, is a List of transcontinental countries, transcontinental country spanning Eastern Europe and North Asia, Northern Asia. It is the List of countries and dependencies by area, largest country in the ...

. The genus is known from two species, ''Rautiania alexandri'' (the

type species In zoological nomenclature, a type species (''species typica'') is the species name with which the name of a genus or subgenus is considered to be permanently taxonomically associated, i.e., the species that contains the biological type specimen ...

) and ''Rautiania minichi'', which differ in aspects of their

maxilla The maxilla (plural: ''maxillae'' ) in vertebrates is the upper fixed (not fixed in Neopterygii) bone of the jaw formed from the fusion of two maxillary bones. In humans, the upper jaw includes the hard palate in the front of the mouth. The t ...

and parietal bones. Certain ''Rautiania'' fossils have helped to reveal certain aspects of weigeltisaurid anatomy and lifestyle which had long alluded paleontologists, such as the component bones of the "crest" at the back of the head, and the large amount of adaptations towards life in the canopies of forests.

Discovery

''Rautiania'' fossils were first discovered during a 2005 paleontological expedition into the

Orenburg Oblast Orenburg Oblast (russian: Оренбургская область, ''Orenburgskaya oblast'') is a federal subject of Russia (an oblast). Its administrative center is the city of Orenburg. From 1938 to 1957, it bore the name ''Chkalov Oblast'' () ...

of Russia. Numerous isolated bones from reptiles of the family Weigeltisauridae were found at the Kul'chumovo-A site. Some of these bones (namely, maxillae and parietals) showed two different morphotypes. In 2006,

Russian Academy of Sciences The Russian Academy of Sciences (RAS; russian: Росси́йская акаде́мия нау́к (РАН) ''Rossíyskaya akadémiya naúk'') consists of the national academy of Russia; a network of scientific research institutes from across t ...

paleontologists Valeriy V. Bulanov and Andrey G. Sennikov described these weigeltisaurid remains as the new genus ''Rautiania'', named after Russian zoologist Aleksandr Sergeevich Rautian (). They named the two different morphotypes as two separate species of ''Rautiania: R. alexandri'' and ''R. minichi''. Both of these species had a single parietal bone as their

holotype A holotype is a single physical example (or illustration) of an organism, known to have been used when the species (or lower-ranked taxon) was formally described. It is either the single such physical example (or illustration) or one of several ...

. The

''R. alexandri'' was also named after Aleksander Rautian, while ''R. minichi'' was named after a different Russian paleontologist, Maksim Georgievich Minikh. Additional ''Rautiania'' bones (of an unspecified species) from both the skull and the rest of the body were described in 2010, along with the implications these new discoveries provided for weigeltisaurid anatomy in general.

Description

Skull

The skull of ''Rautiania'' possessed a number of unique characteristics, which assist in distinguishing members of the genus from other weigeltisaurids, as well as each ''Rautiania'' species (''Rautiania alexandri'' and ''Rautiania minichi'') from each other. The

premaxilla The premaxilla (or praemaxilla) is one of a pair of small cranial bones at the very tip of the upper jaw of many animals, usually, but not always, bearing teeth. In humans, they are fused with the maxilla. The "premaxilla" of therian mammal has b ...

(a toothed bone at the tip of the snout) was long and narrow, with 11 to 13 teeth (More than twice as many as in ''

Weigeltisaurus jaekeli ''Weigeltisaurus'' is an extinct genus of weigeltisaurid reptile from the Late Permian Kupferschiefer of Germany and Marl Slate of England. It has a single species, originally named as ''Palaechamaeleo jaekeli'' in 1930 and later assigned the na ...

''). The

(a toothed bone at the side of the snout) differed between species. ''R. alexandri'' had a maxilla with 30 closely spaced teeth and a ridge under the eye socket. ''R. minichi'', on the other hand, had a maxilla with fewer (23) and more well-spaced teeth and no ridge under the eye socket. ''Rautiania'' teeth were unusually flattened from left-to-right and enlarged from front-to-back. In ''R. alexandri'', this is most pronounced at the rear of the maxilla, and in ''R. minichi'' it is most pronounced at the middle of the maxilla. Premaxillary teeth were small, conical, slightly recurved, and largest towards the rear of the premaxilla. The

surangular The suprangular or surangular is a jaw bone found in most land vertebrates, except mammals. Usually in the back of the jaw, on the upper edge, it is connected to all other jaw bones: dentary, angular, splenial and articular The articular bone i ...

(a bone which forms the upper edge of the rear part of the mandible) had two spikes on its outer surface and a large area for muscle attachment on its inner surface. ''Rautiania'' bones have helped to clarify certain aspects of weigeltisaurid skull anatomy, particularly relating to bones at the rear part of the cranium. As with other weigeltisaurids, the rear part of the skull of ''Rautiania'' had a large hole (known as a temporal fenestra) on each side, edged by bones ornamented with spines, thus forming a sort of "crest". The rear lower corner of the temporal fenestra is now known to have been formed by the

quadratojugal bone The quadratojugal is a skull bone present in many vertebrates, including some living reptiles and amphibians. Anatomy and function In animals with a quadratojugal bone, it is typically found connected to the jugal (cheek) bone from the front and ...

, since a three-dimensionally preserved quadratojugal has been discovered in ''Rautiania''. It was small, possessing a single large spike and firmly connecting to the

quadrate bone The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids (reptiles, birds), and early synapsids. In most tetrapods, the quadrate bone connects to the quadratojugal and squamosal bones in the skull, and forms upper ...

of the jaw joint. The discovery of a quadratojugal in weigeltisaurids reveals that the bone which formed the rear edge of the temporal fenestra was the

squamosal bone The squamosal is a skull bone found in most reptiles, amphibians, and birds. In fishes, it is also called the pterotic bone. In most tetrapods, the squamosal and quadratojugal bones form the cheek series of the skull. The bone forms an ancestral co ...

. The squamosal of ''Rautiania'' was tall and slightly slanted backwards; it was fringed with large spines oriented outwards, as is typical for weigeltisaurids. The upper edge of the temporal fenestra is formed by the

parietal bone The parietal bones () are two bones in the Human skull, skull which, when joined at a fibrous joint, form the sides and roof of the Human skull, cranium. In humans, each bone is roughly quadrilateral in form, and has two surfaces, four borders, an ...

, which differs in structure between ''Rautiania'' species. In ''R. alexandri'', the parietal possesses a row of thin, blocky structures which conjoin at their base. ''R. minichi'', on the other hand, has a row of large, widely spaced spines on its parietal. The upper portion of the postfrontal bone is wider in ''Rautiania'' than in other weigeltisaurids.

Postcranial skeleton

Bulanov & Sennikov (2010) described several noteworthy areas of ''Rautiania'''s skeleton, namely the

sacrum The sacrum (plural: ''sacra'' or ''sacrums''), in human anatomy, is a large, triangular bone at the base of the spine that forms by the fusing of the sacral vertebrae (S1S5) between ages 18 and 30. The sacrum situates at the upper, back part ...

(hip vertebrae),

humerus The humerus (; ) is a long bone in the arm that runs from the shoulder to the elbow. It connects the scapula and the two bones of the lower arm, the radius and ulna, and consists of three sections. The humeral upper extremity consists of a roun ...

(upper arm bone), and manus (hand). The sacrum was formed by three vertebrae, while other weigeltisaurids have (perhaps erroneously) been reported as having two, as in other reptiles. Based on its morphology, the first sacral vertebrae was probably not part of the sacrum ancestrally. The sacrum connects to each ilium (upper plate of the hip) by means of three sacral ribs, one on each side of each vertebra. The second and third sacral ribs were massive, fused to their respective vertebrae and flattened into fan-shaped structures. The first sacral ribs slightly bends backwards, the second extends straight out, and the third slightly bends forwards. The humerus was long, curved, and strongly twisted along its longitudinal axis. Despite the lightly-built structure of the bone, the knobs, ridges, and pits which made up its joints were well-developed. Overall, it closely resembled the humerus of

araeoscelidia Araeoscelidia or Araeoscelida is a clade of extinct diapsid reptiles superficially resembling lizards, extending from the Late Carboniferous to the Early Permian. The group contains the genera ''Araeoscelis'', ''Petrolacosaurus'', the possi ...

n reptiles such as ''

Petrolacosaurus ''Petrolacosaurus'' ("rock lake lizard") is an extinct genus of diapsid reptile from the late Carboniferous period. It was a small, long reptile, and the earliest known reptile with two temporal fenestrae (holes at the rear part of the skull) ...

'' and ''

Araeoscelis ''Araeoscelis'' (from el, αραιά , 'thin' and el, σκελίς , 'ribs of beef') is an extinction, extinct genus of reptile, and one of the earliest diapsids. Fossils have been found in the Nocona Formation, Nocona, Arroyo Formation, Arroyo ...

''. The hand had five digits, with elongated

phalanges The phalanges (singular: ''phalanx'' ) are digital bones in the hands and feet of most vertebrates. In primates, the thumbs and big toes have two phalanges while the other digits have three phalanges. The phalanges are classed as long bones. ...

(finger bones). The phalangeal formula (number of phalanges in each finger) was 2-3-4-5-4, meaning that the fifth finger had one more joint than that of generalized reptiles (which have a phalangeal formula of 2-3-4-5-3). The phalanges also increase in length towards the tip of the fingers, where they abut large, strongly curved

ungual An ungual (from Latin ''unguis'', i.e. ''nail'') is a highly modified distal toe bone which ends in a hoof, claw, or nail. Elephants and ungulates have ungual phalanges, as did the sauropods and horned dinosaurs. A claw is a highly modified ungual ...

s (claws).

Paleobiology

Like other weigeltisaurids, ''Rautiania'' individuals were likely able to glide on skin stretched between bony rods which attached to the torso. Although no ''Rautiania'' specimen preserves these rods, several fossils from this genus do have weight-saving features, as well as adaptations to arboreal life. For example, the

was had an internal structure with open canals and air pockets, making the large crest quite light for its size. The presence of three sacral vertebrae (rather than two as in most reptiles) likely helped the hip absorb the shock of landing on trees after gliding. The lightly-built but strong humerus would have given the animal both better aerial abilities and more flexible climbing abilities. The hand proportions are very similar to those of modern climbing lizards and mammals, further supporting the argument that ''Rautiania'' and other weigeltisaurids were well-adapted for arboreal life. Gliding was likely an adaptation to ease movement between sparse treetops in the upper canopy of forests.

References

{{Taxonbar, from=Q7296266 Prehistoric neodiapsids Permian reptiles of Europe Prehistoric reptile genera