You might think this does not sound like an important find, but I think it is. First, the African late Miocene has a poor hominoid fossil record. Exceptions to this are the mysterious, putative hominins Sahelanthropus, Orrorin, and Ardipithecus kadabba; and the ape-like Chororapithecus, Nakalipithecus, and Samburupithecus. So this new specimen, whether it represents one of the already-known fossil apes or is a new taxon, provides further evidence that apes were present in Africa in this time period. This bears on the debate about whether the living African apes (gorillas and chimpanzees/bonobos) originated in Eurasia or Africa, though certainly more fossils are needed to address this.
Second, most African fossil hominoids are known only from Eastern Africa. As such, it has looked like much of hominoid and hominin evolution have taken place there. At the moment, the only other non-East-African fossil hominoids I can think of are the 13 million year old Otavipithecus mandible from Namibia, and the 7 million year old Sahelanthropus fossils from Chad. So it is clear that hominoids (and hominins) existed in places other than East and South Africa. As the authors note, it is not unlikely that more hominoids (and hominins?) will be discovered in western and central Africa. Who knows, we might even get some (more?) chimpanzee ancestors out of it, which is something I feel paleoanthropology desperately needs.
Pickford M, Coppens Y, Senut B, Morales J, and Braga J. Late Miocene hominoid from Niger. Comptes Rendus Palevol In Press, Corrected Proof.