Gnathostomata: The Evolution of Jaws A. The first gnathostomes were and locomotion more efficient than those of their ancestors.

Question

Gnathostomata: The Evolution of Jaws
A. The first gnathostomes were
and locomotion more efficient than those of their ancestors.
fishes. Key derived traits made their feeding
B. Jawed fishes first appeared in the Paleozoic era.
1. Hinged jaws allow vertebrates to grasp, kill, shred, and crush large food items. Some
species also use their jaws for defense, for grooming, to construct nests, and to transport
their young.
2. The origin of jaws and fins.
a.
b.
Embryological evidence suggests that jaws evolved from paired gill arches in the
pharynx of a jawless ancestor
The earliest fins were folds of skin and moveable spines that stabilized locomotion
and deterred predators. By the Devonian period, most fishes had unpaired (dorsal,
anal, and caudal) and paired (pectoral and pelvic) fins (

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