Audubon's shearwater ill-resolved clade also including such species as the little shearwater, the Manx shearwater ("P. puffinus") or the black-vented shearwater ("P. opisthomelas"). The little-known Heinroth's shearwater ("P. heinrothi") is sometimes considered a subspecies of either Audubon's or the little shearwater. Though it is likely to be another member of that close-knit group, its actual relationships remain uncertain due to lack of specimens. Audubon's shearwater itself has around 10 subspecies. Several have at one time or another been suggested to constitute separate species. For example, the Galápagos Islands population has turned out to be a very distinct species, the Galápagos shearwater ("P.
Trevor H. Worthy the Waitomo frog ("Leiopelma waitomoensis"). In the 1990s Worthy discovered several fossil bird species new to science, including the long-billed wren ("Dendroscansor decurvirostris") in 1991, Scarlett's shearwater ("Puffinus spelaeus") in 1991, and the Niue night heron ("Nycticorax kalavikai") in 1995. In 1991 he also described the Northland skink, a fossil skink species new to science. In 1998 Worthy excavated subfossil bones in Fiji, where he found remains of the flightless Viti Levu giant pigeon ("Natunaornis gigoura"), the Viti Levu scrubfowl ("Megapodius amissus"), the Viti Levu snipe ("Coenocorypha miratropica"), the giant Fiji ground frog ("Platymantis megabotoniviti"), and the small freshwater crocodile