A new species of Cyrenoida (Bivalvia, Cyrenoididae) from the Western Atlantic, with remarks on Cyrenoididae anatomy

Cyrenoida implexa sp. nov. is the first species of Cyrenoididae in the Southern West Atlantic. This new species exhibits external similarities to C. floridana but is distinguished by distinct right hinge dentition, larger siphons and a more extensive siphonal area at the mantle border, an incurrent siphon with three rows of papillae, a lack of papillae at the middle mantle fold, and smaller adductor muscle volume. In the environment, it possesses a higher saline tolerance than C. floridana .