Brachypterygius (meaning ″short wing/paddle″ in Greek) is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from the Late Jurassic of England.McGowan, C. & Motani, R. Ichthyopterygia. In Sues, H.-D. (ed.) Handbook of Paleoherpetology, vol. 8. Verlag Dr. Friedrich Pfeil, Munich, 175 pp., 19 pls. The type species was originally described and named as Ichthyosaurus extremus by Boulenger in 1904.Boulenger, G. A. 1904. Exhibition of, and remarks upon, a paddle of a new species of ichthyosaur. Proceedings of the Zoological Society of London, 1904, 424–426. Brachypterygius was named by Huene in 1922 for the width and shortness of the forepaddle, and the type species is therefore Brachypterygius extremus.Huene, F. F. von 1922. Die Ichthyosaurier des Lias und ihre Zusammenhänge. Verlag von Gebrüder Borntraeger, Berlin, 114 pp., 22 pls. The holotype of B. extremus was originally thought to be from the Lias Group of Bath, United Kingdom, 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-sized ichthyosaur, with a skull length of and a body length up to .McGowan, C. 1976. The description and phenetic relationships of a new ichthyosaur genus from the Upper Jurassic of England. Canadian Journal of Earth Sciences, 13, 668–683. doi:10.1139/e76-070McGowan, C. 1997. The taxonomic status of Grendelius mordax: a preliminary report. Journal of Vertebrate Paleontology, 17, 428–430. doi:10.1080/02724634.1997.10010986 The snout is long, as is characteristic for ichthyosaurs, with larger and more robust teeth, and a relatively smaller eye than Ophthalmosaurus. The basioccipital has a very narrow extracondylar area. The forepaddle may have five or six digits, with the maximum phalangeal count being between 8 and 16. 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.
Taxonomy The holotype of Brachypterygius extremus is a single right forepaddle, clearly different from other Late Jurassic ichthyosaurs (e.g. Ophthalmosaurus). Brachypterygius is closely related to Platypterygius and Caypullisaurus.Fernández M. 2007. Redescription and phylogenetic position of Caypullisaurus (Ichthyosauria: Ophthalmosauridae). Journal of Paleontology 81 (2): 368-375.
Species previously assigned to Brachypterygius Owen (1840) erected Ichthyosaurus trigonus based upon a single dorsal vertebra (ANSP 10124) from the Kimmeridge Clay of Westbrook, Wiltshire, UK.Owen, R. 1840. Report on British Fossil Reptiles. Part I. Report of the British Association for the Advancement of Science, 9, 43–126. The holotype was long thought to be lost until it was rediscovered in 1988.Spamer, E.E., Bogan, A.E. & Torrens, H.S. 1989. Recovery of the Etheldred Benett collection offossils mostly from Jurassic-Cretaceous strata of Wiltshire, England, analysis of the taxonomic nomenclature of Benett (1831), and notes and figures of type specimens contained in the collection. Proceedings of the Academy of Natural Sciences of Philadelphia, 141:115-180. Many specimens were referred to Ichthyosaurus trigonus; Bauer (1898) suggested that – what are now – Ophthalmosaurus, Brachypterygius and Nannopterygius should be synonymised into Ichthyosaurus trigonus.Bauer, F. 1898. Die Ichthyosaurier des oberen weissen Jura. Palaeontographica, 44, 283–328. I. trigonus was included in the new genus Macropterygius by Huene (1922),Huene, F. von. 1922. Die Ichthyosaurier des Lias und ihre Zusammenhange. Monographien zur Geologic and Palaeontologie, 1: 1-114. who later (1923) made it the type species of the genus.Huene, F. von. 1923. Lines of phyletic and biological development of the Ichthyopterygia. Bulletin of the Geological Society of America, 34: 463-468. Nowadays, I. trigonus (and hence Macropterygius) is a nomen dubium because its holotype is indistinguishable from other ophthalmosaurids.Bardet N, Fernández M. 2000. A new ichthyosaur from the Upper Jurassic lithographic limestones of Bavaria.Journal of Paleontology 74 (3): 503-511. (Christopher McGowan and Ryosuke Motani mistakenly stated that I. trigonus may be synonymous with Ophthalmosaurus icenicus)
Richard Lydekker erected the species Ophthalmosaurus cantabridgiensis from the Cambridge Greensand (Albian, Early Cretaceous) of Cambridge, UK, on the basis of a humerus (NHMUK PV OR 43989). McGowan and Motani (2003) considered it to be a species of Brachypterygius, but a 2014 re-assessment of Cambridge Greensand ichthyosaurs found it to be a nomen dubium indeterminate beyond Ophthalmosaurinae. In 2020, Nikolay Zverkov and Dmitry Grigoriev reassigned this species to Maiaspondylus.
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. More complete material from the Kimmeridge Clay of Kimmeridge Bay indicated that these two species were quite similar, so the two genera were synonymised. 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. However, a 2015 publication by Zverkov and colleagues instead found Grendelius mordax to be sufficiently different from Brachypterygius extremus to be considered both a separate genus and species.
Phylogeny The following cladogram shows a possible phylogenetic position of Brachypterygius in Ophthalmosauridae according to the analysis performed by Zverkov and Jacobs (2020).
See also
List of ichthyosaurs Timeline of ichthyosaur research
References