Ognev's mole

The first scientific description of Ognev's mole was made in 1944 by Sergei Uljanowitsch Stroganow under the name Talpa romana ognevi and thus as a subspecies of the Roman mole (T. romana). The comparatively larger size of the animals and their robust tooth structure compared to the Caucasian mole, which occurs further north, was primarily what motivated Stroganov to incorporate the new species into the Roman mole. As a type locality, he gave Bakuriani in the region around Borjomi in southern Georgia. The holotype is formed by an adult male animal originating from there. In addition, Stroganov examined seven other individuals, some of which had been found in the vicinity of Kutaisi. With the specific epithet, Stroganow honored the Soviet zoologist Sergey Ivanovich Ognev.[3][4][5]

In 1989, Ognev's mole was designated as one of three subspecies of the Caucasian mole by Vladimir Sokolov. The distinction was based on size, as the body shape of Ognev's mole stood out as extremely distinctive from the other Caucasian moles. In line with the moles of the Caucasus region and southern Europe, Ognev's mole also has a caecoidal structure of the sacrum (the opening of the foramen on the fourth sacral vertebra is directed backwards). This is a striking difference from the europaeoidal structure (the opening of the foramen on the fourth sacral vertebra is covered by a bone bridge) of the pelvic area in numerous Central and Western European moles.[6][5]

Molecular genetic studies since the 2010s have shown a relatively basal position of the Caucasian moles together with the Altai mole (T. altaica) within the Eurasian moles. The separation of this group dates back to the transition from the Miocene to the Pliocene more than 5 million years ago.[7][4][2] In 2015, genetic analyses showed a clear separation between the moles of the northern and southern Caucasus region. This was supported by the deep divergence between the two lines, which, according to the results, had been distinct since the end of the Pliocene around 3 to 2.5 million years ago. The authors of the study therefore suspected an independent position of Ognev's mole, but omitted a species position, as no genetic material from individuals from the type locality was available to them.[4] Three years later, in the eighth volume of the standard work Handbook of the Mammals of the World, Ognev's mole was granted species status. This separation from the Caucasian mole is also supported by individual cytogenetic data, since the largest chromosome in Ognev's mole has two arms, whereas the Caucasian mole has an acrocentric structure.[5]

Ognev's mole reaches a head-trunk length of 13.4 to 14.2 cm, a tail length of 2.0 to 2.6 cm and a weight of 62 to 91 g. The sexual dimorphism is only slightly pronounced, males are on average 5% heavier than females. With the specified dimensions, Ognev's mole is larger than the closely related Caucasian mole. Outwardly, both types are similar. Like all moles, they are characterized by a cylindrical and robust body, a short neck and shovel-like front feet. The coat color has a blackish gray to black hue. Occasionally, yellowish spots are formed on the muzzle, throat and chest. Similar to the Caucasian mole, but unlike the European mole (Talpa europaea), the eyes are covered with a translucent skin. The rear foot has a length of 1.8 to 2.0 cm.[6][5]

The length of the skull varies between 33.6 and 35.0 mm, the width on the zygomatic arch is 12.1 to 13.7 mm, and the cranium is 15.9 to 17.2 mm. It has a robust rostrum that is between 9.0 and 10.1 mm wide. The dentition has 44 teeth with the following tooth formula: ${\displaystyle {\frac {3.1.4.3}{3.1.4.3}}}$.

Compared to the Caucasian mole, the upper molars are very strong. The upper row of teeth extends over 14.7 to 15.8 mm in length, of which the molars take up 6.0 to 7.4 mm. In proportion, the upper row of teeth takes up around 40% of the length of the skull.[3][8][6][5]

The diploid chromosome set is 2n = 38. It consists of 8 metacentric, 3 submetacentric, 2 subtelocentric and 5 teloacrocentric pairs of chromosomes. The largest chromosome has two arms. The X chromosome is (sub) metacentric, the Y chromosome is speckled.[8][9][10][5]