Steneosaurus (from , 'narrow' and , 'lizard') is a dubious genus of teleosaurid crocodyliform from the Middle or Late Jurassic (Callovian or early Oxfordian) of France. The genus has been used as a wastebasket taxon for thalattosuchian fossils for over two centuries, and almost all known historical species of teleosauroid have been included within it at one point. The genus has remained a wastebasket, with numerous species still included under the label ‘Steneosaurus’, many of which are unrelated to each other (either paraphyletic or polyphyletic with respect to each other and other genera of teleosauroids). Discovery and assigned species The type species, S. rostromajor, was only formally recognised as such in 2020, and this revision determined the type specimen of Steneosaurus was undiagnostic, and so declared the genus Steneosaurus a nomen dubium. The history of this specimen has been detailed in 2017. It was discovered in three pieces by abbot Charles Bacheley (1716-1795) in the Vaches Noires near Villers-sur-Mer (Calvados, France). Bacheley offered these pieces to Alexandre Besson (1725-1809) who had built up an important cabinet of fossils and minerals in Paris. Besson gave one of the pieces (the posterior portion) to Barthélémy Faujas de Saint-Fond (1841-1819), professor of geology in the Muséum national d'Histoire naturelle, Paris. Georges Cuvier first illustrated in 1808 the two anterior pieces of the specimen kept in the Besson collection and then figured the third piece (posterior portion from the Faujas de Saint-Fond collection) in 1824 in association with the anterior pieces (Besson collection) and other cranial remains belonging to Metriorhynchidae. The remaining species referred to Steneosaurus thus require new generic names, and some species have already been assigned to new genera prior to Steneosaurus being declared a nomen dubium. Species in this genus are traditionally classed into two skull groups: longirostrine (long, narrow jaws) and mesorostrine (slightly shorter jaws). Longirostrine S.' atelestatus - Oxfordian Marnes de Villers of France S.' blumembachi - Oxfordian Marnes de Villers of France S.' oplites - Toarcian La Caine-Curcy of France '''S.' rudis - France Reassigned species Steneosaurus' baroni = Andrianavoay Steneosaurus' bollensis = Macrospondylus S.' bouchardi - = Proexochokefalos Steneosaurus' boutilieri = Yvridiosuchus Steneosaurus' brevior = Mystriosaurus Steneosaurus' deslongchampsianus Steneosaurus' edwardsi = Neosteneosaurus '''Steneosaurus' gracilirostris = Plagiophthalmosuchus Steneosaurus' heberti = Proexochokefalos Steneosaurus' larteti = Deslongchampsina Steneosaurus' leedsi = Charitomenosuchus Steneosaurus' megarhinus = Bathysuchus Steneosaurus' megistorhynchus = Seldsienean '''Steneosaurus' obtusidens = Lemmysuchus Classification A 2005 phylogenetic analysis into the