Given that Hou's 1977 description of Wannanosaurus is based on approximately half a skull, a femur, a cervical vertebra, a humerus, a tibia, and part of the pelvic girdle of the type individual, it is quite amazing that there was enough evidence in those few bones to accurately assign Wannanosaurus to a family let alone create a new genus and a new species. The description also takes into account nearby remains which are also partial, but which support the description given by Hou. These remains included a few more vertebrae, two femurs, the left tibia and fibula, part of the pelvic girdle and a foot and claws. Hou used the skull roof, mandible, and teeth mainly in his diagnosis description of Wannanosaurus as a pachycephalosaurid. The description is quite detailed and backs up his diagnosis based on cranial features only found in other members of pachycephalosaur family. As such, that explains how his diagnosis, on very little skeletal remains, has withstood the past thirty plus years of scientific scrutiny. Give it a good read at the link above, it is well worth it.
Hou, Lianhai, "A primitive pachycephalosaurid from
the Cretaceous of Anhui, China, Wannanosaurus yansiensis gen. et sp.
nov," Vertebrata PalAsiatica, Volume 15, Number 3, July, 1977 198-202