Systematic revision of the genus Retrotapes del Río, 1997 (Veneridae: Tapetinae) from the Cenozoic of Chile

ALVAREZ, MAXIMILIANO JORGE; DEL RIO, CLAUDIA JULIA

San Luis

Jornada; RCAPA; 2017

Asociación Paleontológica Argentina

In this contribution we propose a systematic revision and a phylogenetic analysis of several taxa recorded in the Cenozoic of Chile of the well known genus Retrotapes. The first record of this genus proceeds from the Eocene of La Meseta Formation, Marambio Island, Antarctica. It reached the southern extreme of South America in the late Eocene (Loreto Formation, Punta Arenas) represented by R. difficilis. The taxon R. navidadis is a species recorded at both coasts of the continent, in the Guadal Formation (late Oligocene?early Miocene) and the Navidad Formation (early Miocene). Three species are recorded from the Pliocene of central Chile: R. fuenzalidae from La Cueva and Tubul formations, and the extant taxa R. lenticularis (La Cueva and Coquimbo formations) that lives from central Chile to Peru, and R. exalbidus (La Cueva, Coquimbo and Tubul formations) inhabiting from Chiloé to Rio Grande do Sul, Brazil. Based on morphological features previous authors proposed that the mentioned extant species belongs to the genus Eurhomalea and not to Retrotapes. In the performed phylogenetic analysis with 31 terminals and 80 morphological shell characters, R. fuenzalidae was recovered as the sister taxon of a group formed by R. antarcticus (Eocene of La Meseta formation), R. navidadis, R. exalbidus, and R. lenticularis, that is more closely related to a group formed by R. striatolamellatus and R. ninfasiensis (type species), from the Miocene of Patagonia. Therefore, this result reaffirms our systematic assignment because the extant species belongs to Retrotapes and they are not related to Eurhomalea.