Page 24 - The Dinosaur Book and Other Wonders of the Prehistoric World (DK-Smithsonian)

Introduction The Vertebrae ❯ Vertebrates Shoulder
get their name from a
chain of bones called
blade
vertebrae that form the
neck, backbone, and tail.

vertebrates

Until about 530 million years ago, all animals were invertebrates—
creatures with no internal jointed skeletons. But then new types

of animals appeared in the oceans, with bodies strengthened by a
springy rod—the beginnings of a backbone. These evolved into
fish—the first true vertebrates and the ancestors of amphibians,
mammals, reptiles, and birds.

Vertebrate evolution
FISH
Vertebrates make up just 3 percent
of animal species, but they include
all the large animals we are most
JAWLESS FISH BONY FISH SHARKS AND RAYS
familiar with. The first vertebrates
were fish. Some fish evolved
leglike fins and became the
first four-legged land animals
TETRAPODS
(tetrapods). These evolved into
the amphibians, mammals, and
reptiles. The reptiles known as
archosaurs gave rise to the
AMPHIBIANS MAMMALS REPTILES
pterosaurs, dinosaurs, and birds.

TURTLES AND TORTOISES ARCHOSAURS
LIZARDS AND SNAKES MARINE REPTILES

CROCODYLIANS
DINOSAURS AND BIRDS PTEROSAURS

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