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ANIMAL KINGDOM-SHARKS AND JAWLESS FISH

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.


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