Page 180 - Ultimate Visual Dictionary (DK)

ANIMALS

Sharks and

jawless fish SHARKS’ JAWS

SHARKS, DOGFISH (WHICH ARE actually small
sharks), skates, and rays belong to a class
of fishes called Chondrichthyes, which is a
division of the superclass Gnathostomata (meaning “jawed
mouths”). Also sometimes known as elasmobranchs,
sharks and their relatives have a skeleton made of
cartilage (hence their common name, cartilaginous
Jaws of an adult
fish), a characteristic that distinguishes them from
tiger shark
bony fish (see pp. 180-181). Other important features
of cartilaginous fish are extremely tough, toothlike Jaws of a young
tiger shark
scales, and lack of a swim bladder. Jawless fish—
lampreys and hagfish—are primitive, eellike fish EXTERNAL FEATURES
that make up the order Cyclostomata (meaning OF A DOGFISH
“round mouths”), a division of the superclass
Agnatha (meaning “without jaws”). In
addition to their characteristic round,
suckerlike mouths and lack of jaws,
cyclostomes also have smooth,
slimy skin without scales, and
unpaired fins.
Snout

FEATURES OF A Outer lip
LAMPREY’S HEAD
Mouth Eye
Tongue

Sucker Gill slit

Eye
Pectoral fin

Tooth
Anterior dorsal fin
Fringed inner lip
Posterior dorsal fin
EXTERNAL FEATURES OF A LAMPREY

Eye

Gill opening
Anal fin
Caudal fin
Sucker
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