 It was given a relationship-based definition in 2003 by Alexander Kellner, who defined it as the least inclusive clade containing "Anhanguera blittersdorffi", "Pteranodon longiceps", "Dsungaripterus weii", and "Quetzalcoatlus northropi".Later that year, David Unwin suggested a more restrictive definition, in which the clade only contains "Pteranodon longiceps", "Istiodactylus latidens", and their descentants.Brian Andres (2008, 2010, 2014) in his analyses, defined Ornithocheiroidea using the definition of Kellner (2003) to avoid confusion with similarly-defined groups, like Pteranodontoidea.