GEOLOGY

Detailed explanation-1: -Placoderms were the first jawed fish; their jaws likely evolved from the first of their gill arches.

Detailed explanation-2: -Prehistoric armoured fishes called placoderms were the first fishes to have jaws. They arose some time in the Silurian Period, about 440 million years ago, to become the most abundant and diverse fishes of their day.

Detailed explanation-3: -The earliest vertebrates were jawless fishes, and placoderms were among the earliest fishes to evolve jaws, an adaptive breakthrough that contributed to their rapid success.

Detailed explanation-4: -The first record of the jawed Placodermi is from the Early Devonian, about 400 million years ago. The placoderms flourished for about 60 million years and were almost gone at the end of the Devonian. Nothing is known of their ancestors, who must have existed in the Silurian.

Detailed explanation-5: -The first vertebrates to have jaws were the prehistoric armoured fish known as the placoderms, which appeared about 440 million years ago. Both jaw bones and gills are derived from a series of “pharyngeal arches”.