The family Volutidae (Mollusca: Gastropoda) in the Tertiary of Patagonia (Argentina)

DEL RIO, CLAUDIA JULIA; MARTINEZ SERGIO,

Journal of Paleontology

Año: 2006 vol. 80 p. 919 - 945

Abstract--Volutes are widely distributed in the Cenozoic record of Patagonia and Tierra del Fuego, where they are represented by the South American endemic genera Adelomelon Dall, 1906, Pachycymbiola Ihering, 1907, Odontocymbiola Clench and Turner, 1964, and Miomelon Dall, 1907. These taxa have been restricted to the southwestern Atlantic and southeastern Pacific Oceans from Tertiary times to the Recent, and since their earliest record in the ?Middle Eocene-Late Oligocene-earliest Miocene they have evolved adaptations to variations in water depth and temperature. These ecological adaptations were less marked for Adelomelon and Pachycymbiola, which have achieved a similar geographical pattern since the Tertiary, but they were strongly modified in Miomelon. In the Atlantic, Miomelon migrated southwards from the shallow and warm-temperate waters that it typically inhabited during the Tertiary, to deeper, colder waters of the Recent Magellanic Province and Subantarctic region, where it is restricted at present. A detailed discussion of the validity of Tertiary genus Proscaphella Ihering, 1907 herein concludes it to be a synonym of Miomelon Dall, 1907. Seven species are redescribed and illustrated: Adelomelon pilsbryi (Ihering), A. cannada (Ihering), A. (Pachycymbiola) ameghinoi Ihering, ?Pachycymbiola feruglioi (Doello Jurado), Miomelon gracilior (Ihering), M. dorbignyana (Philippi), and M. petersoni (Ortmann); and four new ones are described: Miomelon castilloensis new species, Pachycymbiola chenquensis new species, P. camachoi new species, and P. arriolensis new species.