Elasmosaurus

Elasmosaurus Temporal range: Late Cretaceous, 80.5 Ma PreЄ Є O S D C P T J K Pg N ↓
Elasmosaurus platyurus in the Rocky Mountain Dinosaur Resource Center in Woodland Park, Colorado
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Superorder:	†Sauropterygia
Order:	†Plesiosauria
Family:	†Elasmosauridae
Genus:	†Elasmosaurus Cope, 1868
Species:	†E. platyurus
Binomial name
Elasmosaurus platyurus Cope, 1868

Elasmosaurus (/ɪˌlæzməˈsɔːrəs, -moʊ-/; from Greek ελασμος elasmos 'thin plate' (referring to thin plates in its pelvic girdle) + σαυρος sauros 'lizard') is a genus of plesiosaur with an extremely long neck that lived in the Late Cretaceous period (Campanian stage), 80.5 million years ago.

At 10.3 metres (34 ft) in length,Elasmosaurus was among the largest plesiosaurs. It differs from all other plesiosaurs by having six teeth per premaxilla (the bones at the tip of the snout) and 72 neck (cervical) vertebrae. The skull was relatively flat, with a number of long pointed teeth. The lower jaws were joined at the tip to a point between the fourth and fifth teeth. The neck vertebrae immediately following the skull were long and low, and had longitudinal lateral crests. Like most elasmosaurids, Elasmosaurus had around three pectoral vertebrae. The tail included at least 18 vertebrae.

The pectoral girdle featured a long bar, not present in juveniles. The scapula had margins of approximately equal length for the joint with the coracoid and the articular surface for the upper arm. The anterior edge of the pelvic girdle was made up of three almost straight edges directed to the front and sides of the animal. The ischia, a pair of bones that formed the posterior part of the pelvis, were joined along their medial surfaces. The limbs of Elasmosaurus, like those of other plesiosaurs, were modified into approximately equally sized rigid paddles.