Skates & Rays
Batoidea is a superorder of cartilaginous fishes containing more
than 500 described species in thirteen familes. They are commonly
known as rays, but that term may also be used specifically
for batoids in the order Rajiformes, the "true rays".
Batoids in the family Rajidae are commonly known as "skates".
Batoids are closely related to sharks; indeed according to recent
DNA analyses the catshark is more closely related to the batoids
than to other sharks. Young batoids look very much like young sharks;
relations are also obvious.
Batoids are flat-bodied, and, like sharks, are a species of cartilaginous
marine fish, meaning they have a boneless skeleton made of a tough,
elastic substance. Batoids also are like sharks in having slot-like
body openings called gill slits that lead from the gills. Batoid
gill slits lie under the pectoral fins on the underside, whereas
a shark's are on the sides of the head. Most batoids have a flat,
disk-like body, with the exception of the guitarfishes and sawfishes,
while most sharks have a streamlined body. Many species of batoid
have developed their pectoral fins into broad flat wing-like appendages.
Batoid eggs, unlike those of most other fishes, are fertilized
inside the female's body. The eggs of all batoids except for the
skates (family Rajidae) hatch inside the female and are born alive
(ovoviviparous). Female skates lay internally fertilized flat, rectangular,
leathery-shelled eggs, with tendrils at the corners for anchorage.
Hatched eggs of this type can be found on beaches and are known
as mermaids purses.
Skates are cartilaginous fishes belonging to the family
Rajidae in the superorder Batoidea of rays. They are carnivorous,
feeding mostly on smaller fish and crustaceans. They have flat pectoral
fins continuous with their head, two dorsal fins and a short, spineless
They are benthic (bottom-dwelling) and are found throughout the
world from continental shelves down to the abyssal zone. They are
oviparous fishes, laying eggs in a horny case known as a mermaid's
purse. It is thought that egg-laying in skates is an evolutionary
reversal, that is, skates are descended from ovoviviparous ancestors.
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