What is "megamouth shark"

n. A rare species of deepwater shark, (taxlink Megachasma pelagios species noshow=1), a filter-feeder, swimming with its large mouth wide open to capture plankton and jellyfish.

The megamouth shark (Megachasma pelagios) is a species of deepwater shark. It is rarely seen by humans and is the smallest of the three extant planktivorous sharks, besides the whale shark and basking shark. Since its discovery in 1976, few megamouth sharks have been seen, with 61 specimens known to have been caught or sighted as of April 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 Priabonian M. alisonae and the Oligocene– Miocene M. applegatei – have also recently been proposed on the basis of fossilized tooth remains. However, the Cretaceous-aged M. comanchensis has been recently reclassified as an odontaspid shark in the genus Pseudomegachasma, and is in fact unrelated to the megamouth shark despite similar teeth morphology.