Genus author:
Cope, 1869
Lower Campanian
McAllister Butte, Pierre Shale, Logan County, Kansas, USA.
Referred material (sp.):
Type species:

E. platyurus

Elasmosaurus is one of the most widely recognised plesiosaur names and has become a stereotype for all elasmosaurids. However, it is relatively poorly known. The type and only known specimen of Elasmosaurus platyurus (ANSP 10081) includes the tip of the snout, occipital condyle, and the majority of the vertebral column. It is from the Sharon Springs Member (Lower Campanian) of the Pierre Shale, Logan County, Kansas, USA. The limbs and most of the skull are missing and the pectoral and pelvic girdles, although figured, are also now missing and possibly destroyed (Carpenter 1999). This is unfortunate because based on the figures, the pectoral girdle of Elasmosaurus appears to be atypical for elasmosaurids – it retains a pectoral bar connecting the coracoids to the scapulae on the midline, and a long midline suture between the scapulae.

Elasmosaurus held the record for the greatest number of neck vertebrae (72) in any plesiosaur until the description of Albertonectes (which has 76) in 2012.

Many species of Elasmosaurus have been erected over the years but the majority are invalid or have since been referred to new genera. For example, the genus Libonectes was introduced by Carpenter (1997) for ‘Elasmosaurus’ morgani. Elasmosaurus platyurus is therefore the only valid species belonging to the genus Elasmosaurus.

Skeleton of Elasmosaurus from Cope (1869, revised version)
Elasmosaurus skull elements (from Sachs 2005).
Elasmosaurus painting by Rudolf Zallinger.
Elasmosaurus and mosasaur painting by Zdenek Burian.
Elasmosaurus painting by Zdenek Burian.
Elasmosaurus illustration by me (Adam S. Smith)
Elasmosaurus illustration by Smit
Elasmosaurus painting by Debby Cotter Kaspari, showing detail of the head.