A new, large acteonid gastropod (mollusca) from the latest Cretaceous of Antarctica

Abstract

[Extract] Opisthobranch Gastropods are rare in Mesozoic deposits of Antarctica. The first documented occurrence of opisthobranchs from this continent is from Cretaceous shallow-marine deposits of the James Ross Basin, Antarctic Peninsula, where Wilckens (1910, p. 95–96, pl. 4, fig. 19) described the minute ringiculid Cinulia sp., based on five specimens from two localities on Snow Hill Island. No further work has been done on the Snow Hill Island species. The next mention of Antarctic Cretaceous opisthobranchs was by Zinsmeister et al. (1989, p. 733, fig. 2, p. 734, fig. 3), who cited the occurrence of the ringiculid "Oligoptycha cf. O. concinna Meek and Hayden, 1858," in the lowermost part of Unit 8 of the López de Bertodano Formation (Maastrichtian) on the southern half of Seymour Island (Fig. 1). We report the first record of Acteonidae from the Mesozoic of Antarctica, Acteon (Tenuiactaeon) antarctihadrum n. sp., discovered in shallow-marine Maastrichtian deposits.