Aegirosaurus

Aegirosaurus is an extinct genus of platypterygiine ophthalmosaurid ichthyosaur known from the Late Jurassic and Early Cretaceous of Europe.

Discovery and species
Originally described by Wagner (1853) as a species of the genus Ichthyosaurus (I. leptospondylus), the species Aegirosaurus leptospondylus has had an unstable taxonomic history. It has been referred to the species Ichthyosaurus trigonus posthumus (later reclassified in the dubious genus Macropterygius) in the past, and sometimes identified with Brachypterygius extremus. In 2000, Bardet and Fernández selected a complete skeleton in a private collection as the neotype for the species I. leptospondylus, as the only other described specimen was destroyed in World War II. A second specimen from the Munich collection was referred to the same taxon. Bardet and Fernández concluded that the neotype should be assigned to a new genus, Aegirosaurus. The name means 'Aegir (teutonic god of the ocean) lizard with slender vertebrae'.[1]

Within Ophthalmosauridae, scientists once believed Aegirosaurus was most closely related to Ophthalmosaurus.[2] However, many recent cladistic analyses found it is more closely related to Sveltonectes (and probably to Undorosaurus). Aegirosaurus lineage was found to include Brachypterygius and Maiaspondylus too, and to nest within Platypterygiinae, which is the sister taxon of Ophthalmosaurinae.

Stratigraphic range
Aegirosaurus is known from the lower Tithonian (Upper Jurassic) of Bavaria, Germany. Its remains were discovered in the Solnhofen limestone formations, the same formations that have yielded numerous well-known fossils, such as Archaeopteryx, Compsognathus and Pterodactylus.

In addition to its late Jurassic occurrence, Aegirosaurus has recently been discovered from the late Valanginian (Early Cretaceous) of Southeastern France (Laux-Montaux, department of Drôme; Vocontian Basin), the first diagnostic ichthyosaur recorded from the Valanginian.[5] This shows that most types of Late Jurassic ichthyosaurs crossed the Jurassic-Cretaceous boundary.