Characters:
Ventral cheek margin weakly excavatedPterygoids on palate closed anteriorly (lacks anterior pterygoid vacuity)Platycoelus (flat articulation surfaces) to the vertebraeGreater than 40 cervical vertebraecervical centrum length greater than heightAnterior cervical vertebrae with lateral keel
Aristonectid genera
AristonectesKaiwhekeaMorturneria
The taxon was originally named ‘Turneria seymourensis‘ by Chatterjee and Small (1989) but this genus was preoccupied and so Chatterjee and Creisler (1994) later revised the name to Morturneria seymourensis. The holotype specimen is TTU P 9219, an incomplete skull and mandible plus associated cervical vertebrae, from the Lopez de Bertodano Formation of Seymour Island, Antarctica.
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.
