Reassessment of the Early Cretaceous plesiosaur Cimoliasaurus maccoyi Etheridge, 1904 (Reptilia : Sauropterygia) from White Cliffs, New South Wales

Abstract

Cimoliasaurus maccoyi Etheridge, 1904 is a poorly known plesiosauroid from the lower Cretaceous (Aptian) opal-bearing deposits (Doncaster Member, Wallumbilla Formation) of White Cliffs, New South Wales. Characters used to define the taxon are found to be either uninformative beyond higher taxonomic levels, ontogenetically related or misinterpreted, suggesting that C. maccoyi is a nomen dubium. Provisional referral of the C. maccoyi remains to Elasmosauridae gen. et sp. indet. may be warranted on the basis the derived morphology of its cervical vertebrae. A review of 'cimoliasaurian' taxa described from the Callovian to Maastrichtian of Europe, North and South America, New Zealand and Australia indicates that all can either be reassigned or represent nomina dubia. The taxonomic status of Cimoliasauridae is also tenuous, with the family established on largely non-diagnostic characters.