The most complete specimen of Kawanectes lafquenianum (Sauropterygia, Plesiosauria): New data on basicranial anatomy and possible sexual dimorphism in elasmosaurids

Abstract

Elasmosaurids are a cosmopolitan group of plesiosaurians that radiated during the Late Cretaceous. A new specimen of the small sized elasmosaurid Kawanectes lafquenianum is described here. New features of the basicranium and palate are added: basioccipital tubers with distal end deeply excavated, basioccipital ventral flat plate below occipital condyle, absence of posterior interpterygoid symphysis, parasphenoid extended caudally to the posterior margin of basioccipital condyle, craniocaudally short ventral keel of parasphenoid. Differences recorded between the specimens referred to K. lafquenianum (ilium shape, relative humerus to femur size and sacral centrum proportions) are described. Different explanations of these differences are discussed, concluding that sexual dimorphism is the most plausible explanation.