Introducing Sharks, Skates, Rays, and Chimaeras 11gear. The sharks were relatively small, about 0.75 m (2.5 ft) long. Swell
sharks are unique among sharks because of their ability to gulp water into
their stomach and swell up, probably an antipredator defense that is better
known in bony pufferfishes.
Some discoveries involve spectacular, often larger animals, including a
very large shark and the largest species of ray. In 1976, a very large new
species of shark became entangled in the sea anchor of a naval ship near
Hawaii. Now known as the Megamouth Shark, Megachasma pelagios, this
4- to 5-m (13- to 16.5-ft) open-ocean shark feeds on zooplankton and small
fishes. Dead or dying individuals occasionally wash up on beaches in tropi-
cal and subtropical regions, but fewer than 60 specimens have been found.
Megamouth is certainly the most spectacular shark species to be discovered
in the past century.
In the case of large rays, scientists didn’t find new animals but used
behavior, ecology, and anatomy to reveal that what we thought was one
worldwide species, the Manta Ray, Manta birostris, is actually two species,
M. birostris and M. alfredi. Manta rays evolved from more “normal” sting-
rays and in the process lost the barbed sting characteristic of the ancestral
group. The larger of these two mantas, Giant or Pelagic Manta, M. bi-
rostris, still has a tiny, nonfunctional (“vestigial”) spine, whereas the Reef
Manta, M. alfredi, has lost all vestiges of the sting. The two species also
differ in coloration, migratory behavior, and affinity for shallow water and
reefs.How did sharks get their name?
Controversy surrounds a basic fact about sharks, namely, the origins
of their common name. One possibility is a Mayan word, Xoc, probablyThe 5 -m-long ( 16 -ft) Megamouth Shark was not discovered until 1976 , and fewer than 60 specimens have been found,
most washed up dead or dying on beaches. Who knows what other large shark species remain to be discovered? Draw-
ing by P. Vecsei; used with permission