The thresher shark (Alopias vulpinus), or mango ripi of the Maoris, is very easily recognised by the extremely large upper fluke of the tail, which is as long as the combined length of the head and body. The colour of the thresher is dark-blue above and white below. The mouth and teeth are very small, but it uses its long tail to beat the water and round up small fish upon which it feeds. The thresher is not uncommon in Northland waters and is generally distributed in Australia. It attains a length of 18 ft and a weight of at least 922 lb.
by Arthur William Baden Powell, Assistant Director, Auckland Institute and Museum.