Complex sentence: However, the find was not the first Neanderthal fossil discovery, rather, the true nature and significance had not been recognized on any of the earlier fossils and therefore no separate species' name was assigned.
Split into simpler sentences: However, the find was not the first Neanderthal fossil discovery. Rather, the true nature and significance had not been recognized on any of the earlier fossils, and therefore no separate species' name was assigned.