Megamouth Shark

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Megamouth Shark

Scientific classification

Kingdom:	Animalia
Phylum:	Chordata
Class:	Chondrichthyes
Order:	Lamniformes
Family:	Megachasmidae
Genus:	Megachasma
Species:	M. pelagios

Binomial name

Megachasma pelagios
Taylor, Compagno and Struhsaker, 1983

The Megamouth Shark (Megachasma pelagios) is an extremely rare and unusual species of shark, first seen in 1976, with 32 specimens having been found as of 2005. Like the basking shark and whale shark, it is a filter feeder, consuming plankton and jellyfish, and is distinctive for its large head with rubbery lips. It is so unlike any other type of shark that it is classified in its own family Megachasmidae, though it has been suggested that it may belong in the family Cetorhinidae of which the Basking Shark is currently the sole member.

The first Megamouth was captured on November 15, 1976 about 25 miles off the coast from Kaneohe, Hawaii when it became entangled in the sea anchor of a United States Navy ship. Examination of the 4.5 m (14.6 ft), 750 kg (1,650 lb) specimen by Leighton Taylor showed it to be an entirely unknown type of shark, rivaling the coelacanth as the most sensational discovery in ichthyology during the 20th century.

Since then, several more have been collected in various parts of the world, with the most (five) in the vicinity of Japan. On October 21 1990, Megamouth #6 was found entangled in a drift gillnet off Dana Point, California, taken alive, and then released after tracking devices were attached; it was observed to move close to the surface at night and deeper during the day. The carcass of Megamouth #7 was found in 1994 in Japan and put on display at Marine World Umino-Nakamichi.

The appearance of the Megamouth is distinctive. It has a large mouth with small teeth, and a broad rounded snout - observers have mistaken it for a young orca - a generally brownish-blackish color on top and white underneath, and an asymmetrical tail with a long upper lobe, similar to the Thresher Shark. The interior of its gill slits are lined with finger-like gill rakers that capture its food.

The long delay between initial discovery and the scientific description, which did not happen until 1983, became the focus of an elaborate practical joke by two friends of Leighton Taylor, Richard Ellis of the American Museum of Natural History and John McCosker, director of San Francisco's Steinhart Aquarium: They photocopied random articles from Japanese scientific journals and inserted photographs of the megamouth shark and a map of the type location and an English abstract, making it appear as if a Japanese team under guidance of John E. Randall of the Bishop Museum was to snatch the scientific merits of the description right from under Taylor's nose. An accomplice in Japan then mailed the "preprints" to Taylor, who was naturally dumbstruck. He then had his Japanese-American secretary translate the "paper", only to be told that it contained things like musings about the cat in Japanese art, and rhinoceroses in Ueno Zoo, but nothing about the megamouth shark. Hidden on the last page were the names of Ellis and McCosker, put there deliberately for Taylor to find them. Realizing he had been had, Taylor finally wrote up the description. The remark on its last page, "Particular thanks go to Richard Ellis and John McCosker for preparation of a preliminary manuscript which was of great help in the production of this final paper", is in reference to this incident.

References

Berra, Tim M. (1997): "Some 20th century fish discoveries". Environmental Biology of Fishes 50: 1–12.
Taylor, L.R. et al. (1983): "Megamouth - a new species, genus, and family of lamnoid shark (Megachasma pelagios, family Megachasmidae) from the Hawaiian Islands". Proc. Cal. Acad. Sci. 43A: 87–110.