Phylogenetic reconstructions are still lacking for many molluscan groups, making evolutionary inferences much weaker. The genera Cotonopsis Olsson, 1942 and Cosmioconcha Dall, 1913 are part of the so called Strombina group, and as such have been used as models to study patterns of speciation and extinction brought about by the rise of the Central American gateway. Earlier work, based on a few species of each genus, pointed towards a very close relationship of these genera, which prompted a complete cladistic analysis, including all species of both genera to evaluate the level of relationship. Cladistic analyses based on shell morphology support the monophyly of the group composed by Cotonopsis Cosmioconcha. Cotonopsis as currently defined is paraphyletic and includes Cosmioconcha. Cotonopsis (Turrina) keeps its constituency and may retain its subgeneric status. Cotonopsis sensu stricto should be redefined to include part of Cosmioconcha. Cosmioconcha should be subdivided into two groups. One of these groups should be included in Cotonopsis sensu stricto. The second group should be given subgeneric status. Cotonopsis has a much earlier time of origination and most probably derives from Cosmioconcha. Obtained results give support to some of the evolutionary patterns documented earlier for the Neogene molluscan faunas of tropical America and contribute to a better understanding of the Plio-Pleistocene divergence and turnover events related to the rise of the Panamanian land bridge.
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Vol. 23 • No. 1