SHARKS,
DOGFISH(WHICH ARE actually small sharks.),skates, and rays belong
to a class of fishes called Chondrichthyes ; which is a
division of the upperclassmen Gnathostomata(meaning "jawed mouths")
Sharks and their relatives have a skeleton made of Cartilage (hence their common name ,cartilaginous fish), a characteristics that distinguishes them from bony fishes .Other important features of cartilages fishes are extremely tough tooth-like scales , and lack of swim bladder .Jaw less fish -hag fish and lampreys - are primitive eel like fish that make up the order Cyclostomata(meaning "round mouths"), a division of the super class Agnatha(meaning " without jaws") In addition to their characteristic round , saucer like mouths and lack of jaws cyclostomes also have smooth .slimy skin without scales , and unpaired fins.
Sharks and their relatives have a skeleton made of Cartilage (hence their common name ,cartilaginous fish), a characteristics that distinguishes them from bony fishes .Other important features of cartilages fishes are extremely tough tooth-like scales , and lack of swim bladder .Jaw less fish -hag fish and lampreys - are primitive eel like fish that make up the order Cyclostomata(meaning "round mouths"), a division of the super class Agnatha(meaning " without jaws") In addition to their characteristic round , saucer like mouths and lack of jaws cyclostomes also have smooth .slimy skin without scales , and unpaired fins.
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