The family Cryptoclididae contains a variety of moderately sized long-necked plesiosaurs.
Genera included in this family vary depending on the classification, but the family is now well established with Cryptoclidus, Tricleidus, Pantasaurus, Tatenectes, Kimmerosaurus, Vinialesaurus, Muraenosaurus, and Colymbosaurus included within this group. Some authors have included the derived Cretaceous plesiosaurs Aristonectes and Kaiwhekea within the Cryptoclididae (Cruickshank and Fordyce 2002).
However, more recent studies have classified these Cretaceous taxa as elasmosaurids (Gasparini et al. 2003a), so cryptoclidids are absent from Late Cretaceous strata and mostly restricted to the Jurassic. The range of Colymbosaurus (or other closely related colymbosaurines) may extend the stratigraphic range of typically Jurassic cryptoclidids into the early part of of the Cretaceous Period.
In recent years, some Early Cretaceous probably cryptoclidids have been found. Opallionectes from the Early Cretaceous of Australia is “either an aberrant aristonectine elasmosaurid or, more likely, a late-surviving cryptoclidid” (Kear et al. 2018 p. 463-464), and Abyssosaurus from the Early Cretaceous of Russia has been referred to the Cryptoclididae, making it the youngest known representative of the group (Benson and Druckenmiller 2014, Berezin 2018).
Synapomorphies (shared unique characters) for this group include a narrow vertical jugal bar, an enlarged orbit, and a deeply excavated ventral cheek margin (Brown and Cruickshank 1994).
Classification
Phylogeny
The following internal relationships for cryptoclidids were found by Roberts et al. (2020). They did not identify specific Cryptoclidinae or Muraenosaurinae (=Muraenosaurinae) clades.
After Roberts et al. (2020)
Gasparini et al. (2002) conducted a small cladistic analysis to assess the position of the cryptoclidid Vinialesaurus. They placed Muraenosaurus outside of Cryptoclididae.
After Gasparini et al. (2002)
Cryptoclidid genera
Apractocleidus
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 Leeds and acquired […]
Colymbosaurus
Colymbosaurus is a colymbosaurine (derived cryptoclidid) from the Late Jurassic of the UK and Svalbard, Norway. Two valid species are known, C. megadeirus from the UK, and C. svalbardensis from Svalbard, Norway. The genus is known from the Kimmeridgian, Tithonian, and possibly early Berriasian (Late Jurassic–possibly Early Cretaceous). Benson and Bowdler (2014) revised the genus […]
Cryptoclidus
Cryptoclidus, often wrongly spelled ‘Cryptocleidus’ after Andrews (1909), is a moderately sized plesiosaur with adults about four metres long (Brown 1981). It is known from a large number of individual specimens from the Oxford Clay Formation. Fossils of Cryptoclidus are relatively common, and provide a complete ontogenetic sequence from very young to old adult individuals. […]
Djupedalia
Under construction
Kimmerosaurus
Kimmerosaurus is a poorly known cryptoclidid plesiosaur known only from skull and neck material (Brown 1981, Brown et al. 1986). It differs from other plesiosaurs in the large number of needle-like teeth in its jaws, and in the form of its teeth, which are completely smooth and lack the longitidinal ridges present in other plesiosaurs. […]
Muraenosaurus
Brown (1981) diagnosed Muraenosaurus as follows: “Plesiosauroids in which the teeth are ornamented with many longitudinal ridges; the dentary bears 19 to 22 teeth on each ramus; the premaxillae bear 5 teeth each, of which the 1st and 5th are small, and the 2nd to 4th are large; the most anterior maxilliary tooth (6th upper […]
Opallionectes
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: small needle-like teeth […]
Pantosaurus
Under construction
Spitrasaurus
Under construction
Tatenectes
Under construction
Tricleidus
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 of Tricleidus is […]
