Opallionectes

Post author:Adam S. Smith
Post published:05/02/2026
Post category:Cryptoclididae Genus page Plesiosauria Plesiosauroidea

Opallionectes type specimen (SAM P24560). From Poropat et al. (2023).

Opallionectes is a large, around 5 m long, derived cryptoclidid plesiosauroid from the Early Cretaceous of South Australia. It is known from a partial opalised skeleton, which is mounted for display in the South Australian Museum. The holotype specimen lacks a skull. It is diagnosed by the following unique combination of characters:…

Umoonasaurus

Post author:Adam S. Smith
Post published:31/01/2026
Post category:Genus page Leptocleididae Plesiosauria Plesiosauroidea

Skeleton of Umoonasaurus. (Image copyright Australian Museum: https://australian.museum/blog/museullaneous/a-national-treasure/)

Umoonasaurus is a small (~2.5 m long) leptocleidid that lived during the Early Cretaceous in Southern Australia. The holotype specimen (AM F99374), a spectacular opalised skeleton including the skull, is nicknamed 'Eric'. It is the most complete opalised plesiosaur skeleton (and fossil vertebrate) known. It was originally described briefly as Leptocleidus sp.…