Redescription of two Antarctic species of Cuspidaria: C. concentrica Thiele, 1912 and C. minima (Egorova, 1993) (Bivalvia, Cuspidariidae).

Abstract

Cuspidaria concentrica Thiele, 1912 , frequently reported as a synonym of Cuspidaria kerguelensis Smith, 1885, is re-described and revalidated upon the study of new materials from South Georgia Islands; this constitute the first record of its presence in the Scotia Sea. The more elongated shell outline of C. concentrica and the smaller number of elevated lamellar concentric ridges clearly separate it from C. kerguelensis. Cuspidaria minima (Egorova, 1993), a species known from East Antarctica and South Orkneys Islands, is re-described upon material from Elephant Islands. C. minima is characterized by a small shell with a globose disc strikingly separated from the short rostrum, and shell surface with high, lamellated, bent upwards commarginal ridges. Moreover, anatomical data mainly from septal musculature of both species, are given. Furthermore type specimens of Cuspidaria tenella Smith, 1907, Cuspidaria plicata Thiele, 1912 and Cuspidaria infelix Thiele, 1912 are refigured and the reports on the presence of C. kerguelensis in the Scotia Arc Islands are discussed.