Most of the known specimens of "Stenopterygius", more than 100, were recently redescribed by Michael W. Maisch. 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.