bats and marine mammals, had reached New Zealand before humans did. The discovery of a femur and mandibles of an extinct non-volant (non-flying) mammal in Otago, dated at 16–19 million years old, has changed the view of New Zealand's evolutionary history, as it strongly suggests that mammals had been part of New Zealand's fauna since the break-up of Gondwana. The fossil has been called SB mammal. It is not known when, or why, land mammals became extinct in New Zealand but there were none present on New Zealand for several million years before the arrival of humans. The short-tailed bats (from the monotypic family Mystacinidae), first arrived in the Oligocene or before. These are unique among bats due to their terrestrial foraging habits; this has long been credited to the absence of competing terrestrial mammals, though the presence of the already terrestrial Icarops in the Miocene of Australia shows that their terrestriality evolved in the mainland, while Saint Bathans Fauna mystacine fossils co-existed with another terrestrial mammal, the Saint Bathans mammal. Some plants have evolved with the bats and are fertilised on the ground by the bats. The long-tailed bat (Chalinolobus tuberculatus), a more recent arrival, is relatively common. The Miocene Saint Bathans Fauna also preserves remains of a vesper bat and several incertae sedis species. Birds comprise the most important part of New Zealand's vertebrate fauna. It is uncertain if many birds in New Zealand are descended from Gondwanan stock, as DNA evidence suggests that even the ratites (the kiwis and the moas) arrived after the split from Antarctica. Recent studies suggest that New Zealand wrens are Gondwanan descendants. DNA studies seem to indicate that the wrens are the most ancient of all passerines, splitting from the ancestral passerine stock at the time New Zealand become an isolated land mass. In the absence of mammals, birds diversified into the niches usually filled by mammals in other ecosystems. The moas, of which there were eleven species, were large browsers, and were in turn the prey species of the giant Haast's eagle. Both the moas and the eagle became extinct shortly after the arrival of humans in New Zealand sometime around 1300 CE. It appears that human hunters exterminated the moa populations, which deprived the Haast's eagle of its primary food source, leading to the extinction of that species as well. New Zealand's emblematic kiwis fill the role of small foragers