CENOZOIC BIOGEOGRAPHIC HISTORY OF THE EURYTHERMAL GENUS RETROTAPES, NEW GENUS (SUBFAMILY TAPETINAE) FROM SOUTHERN SOUTH-AMERICA AND ANTARCTICA

Retrotapes, new genus, comprises a group of Neoaustral bivalves that a ppeared in the southern circumpolar regions by the Eocene and have sin ce been confined to the high latitudes of the southern hemisphere. Its presence in the Tertiary strata of Antarctica and southern South Amer ica reflects an active faunal interchange between both regions during the Eocene. Retrotapes is here proposed to include to those Recent and Tertiary representatives of the Subfamily Tapetinae (Family Veneridae ) from southern South America and Antarctica that had been previously placed in Venus Linne, 1758, Marcia H. and A. Adams, 1857, Eurhomalea Cossmann, 1920, Samarangia Dall,1902, and Kalelysia Romer, 1857. The A rgentine Tertiary species Retrotapes ninfasiensis, new species, R, fue goensis, new species, R. striatolamellata (Ihering, 1897) and R, scuta ta (Ihering, 1907) are here described and illustrated. The Recent Arge ntine Venus exalbida Chemnitz, 1795 and Venus lenticularis Sowerby, 18 35, the Antarctic V, antarctica Sharman and Newton, 1894 and V. newton i Wilckens, 1911 (Eocene-early Oligocene?, La Meseta Formation), and t he Neogene Chilean species V. navidadis Philippi, 1887 and V. colchagu ensis Philippi, 1881 are also included in this new genus.