Despite their heavy protection, these primitive fishes weren't built to last. The Devonian ancestors of fishes living today belonged to two main nonarmored groups. The cartilaginous fish, so-called because cartilage formed their skeletons, later gave rise to sharks and rays. They had small, rough scales, fixed fins, and sharp, replaceable teeth. The second group, the bony fish, were covered in scales and had maneuverable fins and gas-filled swim bladders for controlling their buoyancy. Most modern fishes are bony fish.
The bony fish included lobefins. Named after the thick, fleshy base to their fins, lobefins are credited with the giant evolutionary stride that led to the amphibians, making lobefins the ancestors of all four-limbed land vertebrates, including dinosaurs and mammals. The fossils of these remarkable animals come from the red rocks of Devon. Some lobefins are still around today, such as the famous "living fossil" fish, the coelacanth.
A recently discovered fossil creature from the Devonian has been hailed as a vital link between fish and the first vertebrates to walk on land. Found in the Canadian Arctic in 2004, Tiktaalik had a crocodile-like head and strong, bony fins that scientists think it used like legs to move in shallow waters or even on land. The fish showed other characteristics of terrestrial animals, including ribs, a neck, and nostrils on its snout for breathing air.
The first amphibians breathed through simple lungs and their skin. They may have spent most of their lives in the water, leaving it only to escape the attentions of predatory fish.
The first ammonoids also arose during the Devonian. Related to octopuses and squid, these marine animals survived until the end of the Cretaceous period, 65 million years ago.
The bony fish included lobefins. Named after the thick, fleshy base to their fins, lobefins are credited with the giant evolutionary stride that led to the amphibians, making lobefins the ancestors of all four-limbed land vertebrates, including dinosaurs and mammals. The fossils of these remarkable animals come from the red rocks of Devon. Some lobefins are still around today, such as the famous "living fossil" fish, the coelacanth.
A recently discovered fossil creature from the Devonian has been hailed as a vital link between fish and the first vertebrates to walk on land. Found in the Canadian Arctic in 2004, Tiktaalik had a crocodile-like head and strong, bony fins that scientists think it used like legs to move in shallow waters or even on land. The fish showed other characteristics of terrestrial animals, including ribs, a neck, and nostrils on its snout for breathing air.
The first amphibians breathed through simple lungs and their skin. They may have spent most of their lives in the water, leaving it only to escape the attentions of predatory fish.
The first ammonoids also arose during the Devonian. Related to octopuses and squid, these marine animals survived until the end of the Cretaceous period, 65 million years ago.
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