Cenozoic Atlanto-Mediterranean biogeography of Spiricella (Gastropoda, Umbraculidae) and climate change: Filling the geological gap

Abstract. Spiricella unguiculus Rang & Des Moulins, 1828 is a thermophilic opisthobranch species, occurring today in the eastern Atlantic from southern Portugal to Mauritania, and the Mediterranean. However, during its geological history, the species had a much broader geographic distribution, including also the North Sea basin and more northern Atlantic coasts of Western Europe. For more than 150 yr the species was known from a single specimen from the Atlantic Lower Miocene of the Aquitaine basin, France. More recently the species has been recorded from the European Oligocene, Miocene and Recent faunas. The discovery of Spiricella unguiculus in the Pliocene of the Mondego Basin (central-west Portugal) fills the gap existing in the geological distribution of the species. Although the overall recorded occurrences of the species are rare, the Cenozoic geographical distribution of S. unguiculus appears to have undergone a sharp southward contraction. This contraction is in accordance with the general biogeographic trend observed for other Atlanto-Mediterranean gastropod taxa and with the Neogene to Recent Northern Atlantic cooling scenario