Apractocleidus teretipes

Post author:Adam S. Smith
Post published:06/06/2026
Post category:Cryptoclididae Plesiosauria Plesiosauroidea Species page

Tricleidus

Post author:Adam S. Smith
Post published:22/07/2018
Post category:Cryptoclididae Genus page Plesiosauria Plesiosauroidea

Skull of Tricleidus in lateral view. From Brown (1981).

Tricleidus is a cryptoclidid from the Oxford Clay Formation of the UK. The holotype specimen (NHMUK R 3539) consists of disarticulated elements including most of skull and half the postcranium, from the Kosmoceras jasoni – Peltoceras athleta zones from the lowest deposits of the Oxford Clay Formation. The type and only species…

Pachycostasaurus

Post author:Adam S. Smith
Post published:22/07/2018
Post category:Genus page Plesiosauria Pliosauridae Pliosauroidea

Mounted skeleton of Pachycostasaurus in the Peterborough Museum. Photo by Adam Smith.

Pachycostasaurus is approximately 3.1 meters long. Its rib cage and vertebrae exhibit thickened bone (Cruickshank et al. 1996) a condition termed pachyostosis. This heavy ossification is unusual in plesiosaurs (another exception may include Kronosaurus), although it is common in basal sauropterygians, especially pachypleurosaurs. Pachycostasaurus probably used the extra ballast provided by its…

Apractocleidus

Post author:Adam S. Smith
Post published:22/07/2018
Post category:Cryptoclididae Genus page Plesiosauria Plesiosauroidea

Cryptoclidus (the type specimen of 'Apractocleidus', V.1091, with the tail of V.1104 and a replica head) in the Hunterian Museum, Glasgow, Scotland. Photo by Adam S. Smith. 2007.

The genus and species 'Apractocleidus teretipes' was erected by Smellie (1916). Smellie (1915) provided a preliminary account of the specimen before he named it. The specimen is now regarded as an old-adult individual of Cryptoclidus. The taxon 'Apractocleidus' is therefore considered a junior synonym of Cryptoclidus. The specimen was collected by Alfred…