Semicytherura Wagner: its inner lamella and its close allies

The genus Semicythentra Wagner differs from all other members of the Cytherurinae in the nature and course of its inner margin/line of concrescence. The inner lamella is very wide anteriorly. while posteriorly the inner margin extends anteriorly almost to the position of the closing muscles. However. two species examined by the authors, Semicytherura clavata (Brady, 1880) and Semicytherura contraria Zhao & Whatley. 1989. from the SW Atlantic and SE Asia respectively are shown to exhibit this characteristic feature only in the male. In the female of both these species. while the anterior inner lamella is identical to that of the male, posteriorly their inner margins parallel the posterior margin. Similar sex-linkage was show in the genus Angulicytherura which is probably closer to Cytherura than Semicytherura, with a narrow and vestibulate inner lamella. J. Micropalaeontol. 29(1): 1-4. May 2010.