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. Later, it was reassigned to
Brachypterygius because differences between the two species were considered insufficient to warrant separate genera, or even species. 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. Later, Arkangelsky, 1998 described
Brachypterygius zhuravlevi from a Tithonian-stage locality in
Saratov, Russia, subsequently referring it to
Otschevia zhuravlevi. Maisch & Matzke, 2000 considered both Russian taxa to be synonyms of each other, and referred the new combination
B. pseudoscythicus to
Brachypterygius. 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. While McGowan and Motani (2003) considered these Russian taxa to be junior synonyms of
B. extremus, A paper published in 2015 found
Grendelius to be generically distinct from the
Brachypterygius type species and more derived within Platypterygiinae, being more closely related to
Platypterygius than to
Brachypterygius.
Otschevia was considered to be a junior synonym of
Grendelius. }} ==See also==