ichthyosaurs from the Middle Jurassic to the early Late Cretaceous (Bajocian - Cenomanian) worldwide.[1] Almost all ichthyosaurs from the Middle Jurassic onwards belong to the family, until the extinction of ichthyosaurs in the early Late Cretaceous. Ophthalmosaurids appeared worldwide during early Bajocian, subsequent to the disappearance of most other ichthyosaur lineages after the end of the Toarcian.[2] Currently, the oldest known ophthalmosaurids is Mollesaurus from the early Bajocian of Argentina,[3] as well as indeterminate remains of the same age from Luxembourg and Canada.[2] Named by George H. Baur, in 1887, the family contains the basal taxa like Ophthalmosaurus.[1] Appleby (1956) named the taxon Ophthalmosauria which was followed by some authors,[4][5] but these two names are often treated as synonyms; Ophthalmosauridae has the priority over Ophthalmosauria.[1] However, some researchers argue that Ophthalmosauridae should be restricted to the group typically referred to as Ophthalmosaurinae, with classic Platypterygiinae instead being referred to as Undorosauridae or Brachypterygiidae and Ophthalmosauria being used to unite these two groups.[6][7]
Ophthalmosaurus icenicus and all of its descendants". The definition he proposed for Ophthalmosauria was exactly the same.[4] In this case both definitions are synonyms. The cladogram below follows the topology from a 2010 analysis by Patrick S. Druckenmiller and Erin E. Maxwell.[5]
*Note: Placement of Ophthalmosauria by definition.
Fischer et al. (2012) described another new genus of Ophthalmosauridae. They defined for the first time two
monophyletic. Ophthalmosauridae was characterized by a reduced extracondylar area, a plate-like dorsal trochanter, a humerus with a facet for an anterior accessory element and the absence of notching on the paddle elements of the forefin. The cladogram below follows Fischer et al. 2012.[9]
In 2019, two species of Cryopterygius were assigned to the genus Undorosaurus by Zverkov & Efimov (2019). The authors considered the type species of the former genus, C. kristiansenae, to be synonymous with Undorosaurus gorodischensis; second species of Cryopterygius, C. kielanae, was tentatively maintained by the authors as a distinct species within the genus Undorosaurus.[10]
The following cladogram shows a possible phylogenetic positions within Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).[11]
