The genus "Paranthropus" (otherwise known as "robust australopithecines") typically includes "P. boisei", "P. aethiopicus", and "P. robustus". It is debated if "Paranthropus" is a valid natural grouping (monophyletic) or an invalid grouping of similar-looking hominins (paraphyletic). Because skeletal elements are so limited in these species, their affinities with each other and to other australopithecines is difficult to gauge with accuracy. The jaws are the main argument for monophyly, but such anatomy is strongly influenced by diet and environment, and could in all likelihood have evolved independently in "P. boisei" and "P. robustus". Proponents of monophyly consider "P. aethiopicus" to be ancestral to the other two species, or closely related to the ancestor. Proponents of paraphyly allocate these three species to the genus "Australopithecus" as "A. boisei", "A. aethiopicus", and "A. robustus".