Section 1

Introduction to Vertebrates

• Vertebrates are chordates and have a hollow dorsal nerve cord, notochord, pharyngeal pouches, and a post-anal tail at some stage of life.

• The characteristics that distinguish vertebrates from other chordates are vertebrae, a cranium, and an endoskeleton.

• Vertebrates are classified into nine classes: hagfish (class Myxini); lampreys (class Cephalaspidomorphi); sharks and rays (class Chondrichthyes); lobe-finned fishes (class

Sarcopterygii); ray-finned fishes (class Actinopterygii); amphibians (class Amphibia); reptiles (class Reptilia); birds (class Aves); and mammals (class Mammalia).

• Early vertebrates were jawless fishes, which had bony scales, cartilaginous skeletons, and no paired fins.

• Paired fins increased stability and maneuverability in fishes; jaws allowed fish to seize and manipulate prey.

Vocabulary vertebrae (p. 779)

gill arches (p. 781)

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