Grendelius

Size comparison of G. alekseevi

The type species, Grendelius mordax, was described in 1976 on the basis of CAMSM J.68516, a complete skull with associated postcranial elements from the Kimmeridge Clay of England.[2] Later, it was reassigned to Brachypterygius because differences between the two species were considered insufficient to warrant separate genera, or even species.[3][4]

Efimov, 1998 named a new genus of ichthyosaur, Otschevia pseudoscythica on the basis of a single specimen (the holotype) from the Pseudoscythia Zone (late Tithonian stage of the Late Jurassic) of Ulyanovsk, Volga region, Russia.[5] Later, Arkangelsky, 1998 described Brachypterygius zhuravlevi from a Tithonian-stage locality in Saratov, Russia, subsequently referring it to Otschevia zhuravlevi.[6][7] Maisch & Matzke, 2000 considered both Russian taxa to be synonyms of each other, and referred the new combination B. pseudoscythica to Brachypterygius, although they misspelt this as B. pseudoscythius.[8] Thus, Grendelius and Otschevia are considered to be junior synonyms of Brachypterygius. Arkhangelsky named Otschevia alekseevi in 2001, also from the Late Jurassic of Russia.[9] While McGowan and Motani (2003) considered these Russian taxa to be junior synonyms of B. extremus,[4] Maisch (2010) retained them, and B. mordax, as separate species.[10] A new paper published in 2015 found Grendelius and Otschevia generically distinct from the Brachypterygius type species and more derived within Platypterygiinae, being more closely related to Platypterygius than to Brachypterygius.[1]

The following cladogram shows a possible phylogenetic position of Grendelius in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).[11]

• List of ichthyosaurs
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