Brachypterygius

Brachypterygius Temporal range: Late Jurassic, Kimmeridgian–Tithonian PreЄ Є O S D C P T J K Pg N
Brachypterygius pseudoscythica
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	†Ichthyosauria
Family:	†Ophthalmosauridae
Subfamily:	†Platypterygiinae
Genus:	†Brachypterygius von Huene, 1922
Species
†B. alekseevi (Arkangelsky, 2001) [originally Otschevia, possibly B. extremus] †B. cantabrigiensis (Lydekker, 1888) †B. extremus (Boulenger, 1904) von Huene, 1922 (type species) †B. mordax (McGowan, 1976) [originally Grendelius, possibly B. extremus] †B. pseudoscythica (Efimov, 1998) [originally Otschevia, possibly B. extremus]
Synonyms
Brachypterygius zhuravlevi Arkangelsky, 1998 (later Otschevia zhuravlevi (Arkhangelsky, 1998) Arkhangelsky, 2000 Brachypterygius pseudoscythius Maisch & Matzke, 2000 (lapsus calami) Grendelius McGowan, 1976 Otschevia Efimov, 1998

Brachypterygius (meaning ″wide wing/paddle″ in Greek) is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from the Late Jurassic to Early Cretaceous of England, France, European Russia and possibly Madagascar.^[1] The type species was originally described and named as Ichthyosaurus extremus by Boulenger in 1904.^[2] Brachypterygius was named by Huene in 1922 for the width and shortness of the forepaddle, and the type species is therefore Brachypterygius extremus.^[3] The holotype of B. extremus was originally thought to be from the Lias Group of Bath, UK, but other specimens suggest it more likely came from the Kimmeridgian Kimmeridge Clay (Late Jurassic) of Kimmeridge Bay, Dorset, UK.

Description

Brachypterygius is a medium to large ichthyosaur, with a skull length of 0.5–1.2 m.^[4][5] The snout is long, as is characteristic for ichthyosaurs, with larger and more robust teeth, and a relatively smaller eye than Ophthalmosaurus.^[5] The basioccipital has a very narrow extracondylar area.^[5] The forepaddle may have five or six digits, with the maximum phalangeal count being between 8 and 16.^[2][5] A key feature is the three facets at the distal end of the humerus; the middle is the smallest and articulates with the intermedium, which clearly separates Brachypterygius from Ophthalmosaurus, the most common Late Jurassic ichthyosaur.^[2]

Taxonomy

The holotype of Brachypterygius extremus is a single right forepaddle, clearly different to other Late Jurassic ichthyosaurs (e.g. Ophthalmosaurus).^[2] A large skull was discovered in the Kimmeridge Clay of Stowbridge, Norfolk, UK and named as a new genus and species, Grendelius mordax, by McGowan in 1976.^[4] More complete material from the Kimmeridge Clay of Kimmeridge Bay united these two specimens and the two genera were duly synonymised.^[5] In 2003, McGowan & Motani synonymised the two species B. extremus and B. mordax into B. extremus, considering differences in the forepaddle to be of insufficient taxonomic value.^[1] Other species within Brachypterygius include B. cantabridgiensis from the Cambridge Greensand (Albian, Early Cretaceous) of Cambridge, UK, which is only known from a humerus.^[6]

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.^[7] Later, Arkangelsky, 1998 described Brachypterygius zhuravlevi from a Tithonian-stage locality in Saratov, Russia, subsequently referring it to Otschevia zhuravlevi.^[8][9] 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.^[10] 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.^[11] While McGowan and Motani (2003) considered these Russian taxa to be junior synonyms of B. extremus,^[1] Maisch (2010) retained them, and B. mordax, as separate species.^[12] Poor preservation and description makes it difficult to be certain of their affinities.

Brachypterygius is closely related to Platypterygius and Caypullisaurus.^[13]

Ichthyosaurus trigonus

Owen (1840) erected Ichthyosaurus trigonus based upon some vertebrae from the Kimmeridge Clay of Westbrook, Wiltshire, UK.^[14] The specimens are lost, but their description is not clearly different to any other Late Jurassic ichthyosaur. McGowan & Motani (2003) thought they may represent Ophthalmosaurus icenicus.^[1] Many specimens have been referred to Ichthyosaurus trigonus; Bauer (1898) suggested that – what are now – Ophthalmosaurus, Brachypterygius and Nannopterygius should be synonymised into Ichthyosaurus trigonus, as this is the older name.^[15] At least some specimens (especially humeri) are referrable to Brachypterygius, although it is unlikely this species is entirely synonymous with it, and is probably a collection of several taxa.

References