Category «Elasmosauridae»


The holotype specimen (KUVP 1301) of Styxosaurus is an articulated skull and anterior portion of the neck. It was found in the Niobrara Chalk near Hell Creek, Logan County, Western Kansas in 1890. It was described later that year as a new species Cimoliosaurus snowii by Williston (1890a) (and Williston 1890b), who subsequently (Williston 1906) referred the species to Elasmosaurus.


The type skeleton of ‘Ogmodirus’ was collected in 1909 by C. Boyce from the upper Greenhorn Limestone Formation (Lower Turonian, Late Cretaceous) of Cloud County (near Aurora), Kansas (Storrs 1999, Schumacher and Everhart 2005). The specimen, KUVP 441, is a partial skeleton consisting of partial vertebral column (51 cervical vertebrae, 18 caudal vertebrae), limb, and girdle elements.


The Elasmosauridae is a group of very long-necked plesiosaurs. They form a major component of Late Cretaceous plesiosaur assemblages. The definition of Elasmosauridae has changed in recent years as our understanding of plesiosaur evolution has improved. Older definitions included many Jurassic long-necked forms (Bardet et al.