Plesiosauroids in which the teeth are ornamented with many longitudinal ridges; the dentary bears 17 teeth on each ramus; the premaxilae bear 5 teeth each, of which the 1st and 5th are small and the 2nd to 4th large; the most anterior maxilliary tooth (6th upper tooth) is small and the 8th and 9th upper teeth are large; the parietals form a sagital crest; the quadrate overlaps the quadrate ramus of the pterygoid posteromedially; the paroccipitial process of the exocciptial-ophisthotic is relatively long and slender; the pterygoid bears a process for union with the basisphenoid; the occipital condyle is ringed by a groove, and is formed from the basioccipital only; there are at least 26 and possibly slightly more cervical vertebrae with realtively amphicoelous centra, the length of which only slightly exceeds the height (but never the width) in the most anterior vertebrae; the clavicles are tiriangular and wellp-developed, and lie visceral to the interclavicle which separates them in the midline; the interclavicle is well-developed and plate-like; the coracoids meet the scapulae in midline in 'adults'; the width of the posterior cornua of the coracoids exceeds the interglenoid widt in 'adults'; the humerus is not greatly expanded distally, and articulates with four epipodials

Greek, tri-, 'three', Greek, kleid- (kleis), 'key, clavicle': Triple clavicle.