It was named in 1928 by
Charles W. Gilmore for jaw and skull bones found in the
Lance Formation and
Hell Creek Formation of
Wyoming and
Montana. Gilmore also named the species
P. obtusa in 1928, but it is now considered a junior synonym, separated by features caused by erosion. Additional specimens were referred to
Parasaniwa from the
Lower Eocene Bridger Formation, but additional material from the
Wasatch Formation instead suggests that this belongs to a separate genus
Parasaniwa is considered closely related to
Necrosaurus as a member of Necrosauridae, though it has at times been kept in a separate family Parasaniwidae. ==References==