The whale shark (Rhincodon typus) is a slow-moving, filter-feeding carpet shark and the largest known extant fish species. The largest confirmed individual had a length of 18.8 m (61.7 ft).[9] The whale shark holds many records for size in the animal kingdom, most notably being by far the largest living nonmammalian vertebrate. It is the sole member of the genus Rhincodon and the only extant member of the family Rhincodontidae, which belongs to the subclass Elasmobranchii in the class Chondrichthyes. Before 1984 it was classified as Rhiniodon into Rhinodontidae. The whale shark is found in open waters of the tropical oceans and is rarely found in water below 21 °C (70 °F).[2] Studies looking at vertebral growth bands and the growth rates of free-swimming sharks have estimated whale shark lifespans at 80–130 years.[10][11][12] Whale sharks have very large mouths and are filter feeders, which is a feeding mode that occurs in only two other sharks, the megamouth shark and the basking shark. They feed almost exclusively on plankton and small fishes, and pose no threat to humans. The species was distinguished in April 1828 after the harpooning of a 4.6 m (15 ft) specimen in Table Bay, South Africa. Andrew Smith, a military doctor associated with British troops stationed in Cape Town, described it the following year.[13] The name "whale shark" refers to the fish's size: it is as large as some species of whale.[14] In addition, its filter feeding habits are not unlike those of baleen whales.