The
megamouth shark (
Megachasma pelagios) is an extremely rare species of deepwater
shark, and the smallest of the three
planktivorous sharks, besides the
whale shark and
basking shark. Since its discovery in 1976, few megamouth sharks have been seen, with
60 specimens known to have been caught or sighted as of January 2015, including three recordings on film. Like the other two
filter-feeders, it swims with its enormous mouth wide open, filtering water for
plankton and
jellyfish. It is distinctive for its large head with rubbery lips. It is so unlike any other type of shark that it is usually considered to be the sole extant species in the distinct family
Megachasmidae, though suggestion has been made that it may belong in the family
Cetorhinidae, of which the basking shark is currently the sole extant member. In addition to the living
M. pelagios, however, two extinct megamouth species – the
Cretaceous M. comanchensis and the
Oligocene–
Miocene M. applegatei – have also recently been proposed on the basis of fossilized tooth remains.