 A 2013 study by Benson and colleagues found "Umoonasaurus" to be a close relative of "Leptocleidus" and to belong to Leptocleidia, which was found to belong to Plesiosauroidea.In 2015, Parrilla-Bel and Canudo found "Umoonasaurus" to be a leptocleidid, and in turn finding Leptocleididae to belong to Leptocleidia, which was once again recovered as a member of Plesiosauroidea.Subsequent analyses have recovered a placement for "Umoonasaurus" similar to the two previous studies.