List of largest fish
Fish vary greatly in size. The whale shark and basking shark exceed all other fish by a considerable margin in weight and length. Fish are a paraphyletic group that describes aquatic vertebrates while excluding tetrapods, and the bony fish that often represent the group are more closely related to cetaceans such as whales, than to the cartilaginous fish such as sharks and rays. As such, cross group comparisons on this page only serve a colloquial purpose. Armored fish (Placodermi). The largest known fishes of the now-extinct class Placodermi were "Dunkleosteus" and "Titanichthys". These particular animals  may have reached lengths of and are estimated to have weighed 3.6 tons. Cartilaginous fish (Chondrichthyes). The cartilaginous fish are not directly related to the "bony fish," but are sometimes lumped together for simplicity in description. The largest living cartilaginous fish, of the order Orectolobiformes, is the whale shark ("Rhincodon typus"), of the world's tropical oceans. It is also the largest living animal that is not a cetacean and, like the largest whales, it is a docile creature that filter-feeds on tiny plankton. An average adult of this species measures long and weighs an average of 9 tonnes . The largest verified specimen was caught in 1949 off Karachi, Pakistan and was long and weighed 21.5 tonnes. Although many are dubious, there are several reports of larger whale sharks, with reliable sources citing unverified specimens of up to 37 tonnes and . Spiny sharks (Acanthodii). The largest of the now-extinct Acanthodii was "Ischnacanthus". Some species were of large size, up to 2 m in length. Bony fish (Osteichthyes). Ray-finned fish (Actinopterygii). The largest living bony fish (superclass Osteichthyes, which includes both ray-finned and lobe-finned fish) is the widely distributed ocean sunfish ("Mola mola") and southern sunfish  ("Mola alexandrini"), both being members of the order Tetraodontiformes. The record size ocean sunfish crashed into a boat off Bird Island, Australia in 1910 and measured from fin-to-fin, in length and weighed about , while the biggest "Mola alexandrini" was also coincidentally 2,300 kg in mass and 3.0 m in length, caught off in 1996 and misidentified as a "Mola mola". As for length, the longest extant bony fish on earth is the giant oarfish ("Regalecus glesne"). Slender and compressed, it averages over long at maturity. A specimen caught in 1885 of in length weighed . The longest known example , which was hit by a steamship, was measured as long. Much larger bony fish existed prehistorically, the largest ever known having been "Leedsichthys", of the Jurassic period in what is now England. This species is certainly the largest bony fish ever and perhaps the largest non-cetacean marine animal to have ever existed. Estimates of the size of this fish range from and mass from 20 to 50 tons. A maximum size of and 25–30 tons has been deemed to be most realistic. Lobe-finned fish (Sarcopterygii). The largest living lobe-finned fish is the coelacanth. The average weight of  the living West Indian Ocean coelacanth, ("Latimeria chalumnae"), is , and they can reach up to in length. Specimens can weigh up to . The largest lobe-finned fish of all time was "Rhizodus" at up to .