Nochnitsa is a genus of gorgonopsian (predatory therapsids, the group including modern mammals) that lived during the Permian period in what is now Russia. The first fossil was found at the Kotelnich locality near the Vyatka River and was made the holotype of the new genus and species N. geminidens in 2018. The generic name refers to the Nocnitsa, an evil nocturnal spirit from Slavic mythology, and is intended as a regional counterpart to the Gorgons of Greek mythology, often referenced in the names of the group. The specific name, meaning "twin tooth", alludes to its paired autapomorphic postcanine teeth. The holotype specimen consists of a near complete skull associated with some partial postcranial bones. With an approximately 8 cm (3.1 in) long skull, Nochnitsa was a relatively small gorgonopsian. The snout was elongated, and the teeth were generally inclined backward, pointed, and serrated. The canines (the saber teeth) were much larger than the incisors at the front and postcanines behind but relatively small for a gorgonopsian. Nochnitsa was distinct from other members of the group by the arrangement of its upper postcanine teeth, which were paired and separated by short diastema (gap). Its lower jaw, very similar to that of therocephalians, lacked the characteristic mentum ("chin") of gorgonopsians and exhibited a low mandibular symphysis. The known elements of the postcranial skeleton do not show notable differences compared to those of other gorgonopsians. They indicate, however, a gracile humerus, the apparent absence of reduced, disc-shaped phalanges typically present in the group, and possible metacarpals among the largest known among gorgonopsians. Since its formal description, phylogenetic analyzes found Nochnitsa to be the earliest-diverging gorgonopsians known, followed by Viatkogorgon, also from Kotelnich. All other gorgonopsians appear to belong to two, later-diverging Russian and African groups. The age of the Vanyushonki Member of the Kotelnich succession, from which Nochnitsa is known, is not determined but is thought to date to either the late or middle Permian epoch. The small size of Nochnitsa compared to its contemporary Viatkogorgon and the therocephalians from this locality suggests that it occupied a comparatively minor predatory role.
Discovery and naming
The only known specimen of Nochnitsa was discovered in 1994 by the Russian paleontologist Albert J. Khlyupin at the Kotelnich locality of Kotelnichsky District, in Russia's Kirov Oblast, a region known for its Permian exposures on the banks of the Vyatka River. After being collected, the specimen was transferred to the Paleontological Museum of Vyatka, where it is since catalogued as KPM 310. Following preparation, it consists of a nearly complete and relatively well-preserved skull associated with a partial skeleton, including ribs, the axial portion of the vertebral column, and an incomplete right forelimb. While the left side of the skull is well preserved, the right side is laterally compressed and largely obscured by forelimb elements embedded in the rock matrix. Some sutures remain difficult to distinguish, and the snout exhibits several surface crackings. A large crack extending from the anterior margin of the left eye socket to the right temporal fenestra has been filled with plaster, and other smaller cracks have been repaired with silicone rubber. Furthermore, the surface of the palatine bone is completely obscured by the occluded mandible. In a 2018 paper, the American paleontologist Christian F. Kammerer and his Russian colleague Vladimir Masyutin described the specimen as the holotype of a new genus and species of gorgonopsian, Nochnitsa geminidens. The generic name Nochnitsa refers to the Nocnitsa, a nocturnal evil spirit from Slavic mythology. It is intended as a regional counterpart to the Gorgons of Greek mythology, which are the namesake of many genera within Gorgonopsia. The specific epithet geminidens is derived from the Latin geminus, "twin" and dens, "tooth", in reference to the paired autapomorphic postcanine teeth of the animal. Russian gorgonopsid discoveries began in the 1890s with the finding of Inostrancevia, one of the largest members of the group. Few additional finds were made over the two next centuries; Nochnitsa thus represents the first valid gorgonopsian described from Russia since Suchogorgon in 2000, the country remaining the only place outside Africa where the group is definitely known. Nochnitsa also represents the second gorgonopsian described from Kotelnich after Viatkogorgon in 1999; on that occasion, Kammerer and Masyutin redescribed the holotype skull of the latter in order to compare it with that of the new taxon.
Description
Skull
Nochnitsa was a particularly small gorgonopsian, with the holotype possessing a skull measuring 82 mm (3.2 in) in length. For comparison, the largest Late Permian gorgonopsians such as Inostrancevia and Rubidgea reached skull lengths in excess of 40 cm (16 in). The snout of Nochnitsa was relatively elongate for a gorgonopsian. The premaxilla (the frontmost bone of the upper jaw) was little exposed on the side surface of the snout, as in Viatkogorgon. As in most gorgonopsians, five incisors (front teeth) are present on each side. The upper incisors are slightly recurved, with clear serrations towards their tips. As in Viatkogorgon, it remains uncertain whether their size decreased posteriorly along the tooth-row, as the only two intact incisors of their holotypes correspond to the same tooth position on each side (I5). In general, the teeth were pointed, flattened on the outer side, and somewhat convex on the inner side, and the serrated area of each tooth was displaced towards the outer edge of the crowns. The septomaxilla (a small bone between the nasal bone and the maxilla, the main bone of the upper jaw) had a longer side facing process than Viatkogorgon.
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