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".