Page 41 - The Dinosaur Book and Other Wonders of the Prehistoric World (DK-Smithsonian)

Unlike modern
sharks, the mouth
was at the tip of the Pikaia was a primitive
snout rather than chordate—an animal with
on the underside. Cladoselache a spinal cord but no bones.
Pikaia

The strange flat-topped
structure on the back of
males may have been used
to attract a female.
A long, flat body The age of f
extended from behind
Pikaia’s small head.
Stethacanthus ish
had many
tooth-like

scales
on its head and
dorsal fin.

This armored
fish had a bony
head shield.

Coccosteus fossil

The shark’s sleek, streamlined
body was adapted for fast Large scales
movement through the water. covered the body of
this lobe-finned fish.

Holoptychius

The paired fins under
the body contained
strong limb bones.

evolved—sharks like Stethacanthus and lobe-finned fish, they were the first vertebrates
Cladoselache had skeletons made of a rubbery to crawl out of the water and live on land. Fish
material called cartilage, while the so-called have continued to flourish ever since; even
bony fish like Cheirolepis had skeletons of though the largest mass extinction wiped out
hardened bone. Some of these fish also had four 90 percent of marine species 251 million years
stout, bony fins beneath their bodies. Called the ago, fish managed to survive. 39

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