First complete description of the dark-mouth skate Raja arctowskii Dollo, 1904 from Antarctic waters, assigned to the genus Bathyraja (Elasmobranchii, Rajiformes, Arhynchobatidae)

The dark-mouth skate, Raja arctowskii Dollo, 1904 from Antarctic waters is an extraordinary case in skate taxonomy. For more than 100 years, this species has been known only from three empty egg capsules and the species as such has remained undescribed due to the lack of specimens that could be assigned to Dollo's small capsules. Since trawled egg capsules and an egg capsule containing a near-term embryo became available, it finally was possible to connect specimens with the empty egg capsules and completely describe Dollo's R. arctowskii with detailed external morphology, skeletal features, clasper morphology, and clasper skeleton and assign it to the genus Bathyraja Ishiyama, 1958a. Bathyraja arctowskii is one of the smallest known species of Bathyraja, attaining only a 61 cm total length (TL). It is characterized by an at least partly, usually completely medium to dark grayish pigmented mouth cavity, as well as the often dark underside of the nasal curtain from very small juvenile stages onwards. It further differs from most congeners in Antarctic and Subantarctic waters in the absence of thorns on the dorsal disc. It appears to be a wide-ranging, circumantarctic species found in the Atlantic, Pacific, and Indian Ocean sectors of the Southern Ocean. The species seems to be locally common at least in the Atlantic sector, with up to 94 juvenile to subadult specimens caught in one single haul.

Automated summary

The dark-mouth skate, Raja arctowskii Dollo, 1904 from Antarctic waters is a unique case in skate taxonomy that has been known for over 100 years but remained undescribed due to lack of specimens. It is one of the smallest species in the genus Bathyraja, characterized by specific features and a wide-ranging distribution in the Southern Ocean.