Later described as the first known member of "Australopithecus afarensis". The footprints were classified as possibly belonging to "Australopithecus afarensis". AL 129-1 is a fossilized knee joint of the species "Australopithecus afarensis". One of the most valuable pieces is the cast of an "Australopithecus afarensis" skeleton. "Australopithecus afarensis" fossils have only been discovered within Eastern Africa. The researchers believe that, like Lucy, the fossils probably belong to the species "Australopithecus afarensis". Ancestors such as "Australopithecus afarensis" did have air sacs, as do other great apes. The specimen is a distant cousin of the "Australopithecus afarensis", Lucy's species. "H. habilis" is considered to be intermediate between "Australopithecus afarensis" and "H. erectus". The most well known hominid discovery is "Australopithecus afarensis" (Lucy). Gracile australopithecines ("Australopithecus afarensis") emerge in the same region, around 4 million years ago.