Stenopterygius
Stenopterygius is an extinct genus of thunnosaur ichthyosaur known from Europe (England, France, Germany, Luxembourg and Switzerland).[1][2] This genus of ichthyosaur grew to a maximum length of 4 meters (13 feet).[1][3][4]
Stenopterygius was originally named by Quenstedt in 1856 as a species of Ichthyosaurus, I. quadriscissus. Otto Jaekel in 1904 reassigned it to its own genus, Stenopterygius. The type species is therefore Stenopterygius quadriscissus.[2] The generic name is derived from stenos, Greek for "narrow", and pteryx (πτερυξ), Greek for "fin" or "wing".[4]
Stenopterygius was physically similar to the better known Ichthyosaurus, but had a smaller skull and narrower flippers. Beautifully preserved fossils of Stenopterygius have been found in Germany.[5] Its skull was extended into a kind of a beak and was armed with a quantity of large teeth. The limbs had been transformed to fin-like structures. The tail terminated in a large, semicircular, leathery, vertical caudal fin and even a triangular dorsal fin was present. One well-preserved fossil of Stenopterygius preserves traces of skin, from which the animal's coloration was discovered to be countershaded (darker on the back than the underbelly).[6]
Most of the known specimens of Stenopterygius, more than 100, were redescribed by Michael W. Maisch in 2008. He found that S. quadriscissus (the type species) also includes S. eos, S. incessus, and S. macrophasma, as well as specimens previously referred to S. hauffianus and S. megacephalus. Maisch followed Woodward (1932) and considered Ichthyosaurus triscissus to be a valid species of Stenopterygius. The type specimens of S. longifrons, S. megacephalus, and S. megalorhinus were all referred to this species, as the name I. triscissus has a priority over them. Some specimens previously referred to S. megalorhinus, as well as the holotype of S. cuneiceps, were found to belong to a species of their own for which the binomen Stenopterygius uniter can be used.[2]
As the holotype of S. uniter was destroyed in World War II, Maisch proposed a neotype. Maisch also found that S. promegacephalus is a nomen dubium, as it is based on a juvenile specimen, and that the lectotype of S. hauffianus can be determined as Stenopterygius cf. S. quadriscissus at best, so this species should be considered a nomen dubium. He found out that most specimens previously referred to S. hauffianus can be referred to S. quadriscissus, while the rest belongs to a highly distinctive new taxon that cannot be referred to any valid species of Stenopterygius. This species was reassigned to its own genus, Hauffiopteryx.[2]
_(19777856284).jpg/440px-The_dinosaur_book_-_the_ruling_reptiles_and_their_relatives_(1951)_(19777856284).jpg)
_(19777856284).jpg){kind=link}