Temporal range: Late Cretaceous
Elasmosaurus sp by ashere-d5i4md1.jpg
An artist's illustration of Elasmosaurus platyurus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Superorder: Sauropterygia
Order: Plesiosauria
Family: Elasmosauridae
Genus: Elasmosaurus
Cope, 1868
Species: E. platyurus
Type species
Elasmosaurus platyurus


Elasmosaurus was a type of long-necked plesiosaur, belonging to the family of Elasmosauridae, the order of Plesiosauria, and the suborder of Plesiosauroidea. It belongs to the family that consists of the longest-necked plesiosaurs. Elasmosaurus thrived during the Cretaceous Period, and lived on a diet of fish and other small sea creatures of that time. They typically reached around 10–14 meters in total body length, with a neck that counted for over half of its body length.
Elasmosaurus is the largest of all plesiosaurs, with a neck that consisted of 70 vertebrae that counted for over half of the massive animal's total body length: fourteen meters. Elasmosaurus is the type species for the family of Elasmosauridae and was closely related to other elasmosaurid plesiosaurs such as Hydrotherosaurus and Thalassomedon.