Cryptoclidus, often wrongly spelled ‘Cryptocleidus’ after Andrews (1909), is a moderately sized plesiosaur up to 3 metres long. It is known from a large number of individual specimens from the Oxford Clay Formation. Fossils of Cryptoclidus are relatively common, and provide a complete ontogenetic sequence from very young to old adult individuals.
Under construction
Skeleton of Brancasaurus in side view. From Sachs et al. (2016)
Skull of Brancasaurus in dorsal and lateral view, and showing the tip of the snout (C) in ventral view (from Wegner 1914)
The mysterious plesiosaur Aristonectes is notable for its mouthful of pin-like teeth. A special feeding guild, the ‘trap guild’, has been proposed to accommodate Aristonectes and other plesiosaurs with similar dentition (Chatterjee and Small 1989) such as Cryptoclidus, Kimmerosaurus, and Kaiwhekea.
The genus and species ‘Apractocleidus teretipes‘ was erected by Smellie (1916) for a specimen now regarded as old-adult individual of Cryptoclidus. The specimen was collected by Alfred Leeds and acquired by the Hunterian Museum, Glasgow.
Albertonectes is a very long-necked elasmosaurid from the Late Cretaceous of Alberta, Canada. The holotype specimen (TMP 2007.0110001) consists of an almost complete skeleton lacking a skull (Kubo et al. 2012). The neck contains 76 cervical vertebrae, which is a unique character of Albertonectes vanderveldei and the highest number of neck vertebrae known for any plesiosaur, surpassing the previous record-holder (Elasmosaurus) by four vertebrae.
It was once common knowledge that elasmosaurid plesiosaurs were bendy-necked beasts that swanned about near the surface, striking snake-like at slippery prey. It is now common knowledge that their necks were relatively rigid rod-like structures, the function of which remains something of a mystery.
