.Marine life
The Devonian Period was a time of extensive reef building in the shallow water that surrounded each continent and separated Gondwana from Euramerica. Reef ecosystems contained numerous brachiopods, still numerous trilobites, tabulate and horn corals. Placoderms (the armored fishes) underwent wide diversification and became the dominant marine predators. Placoderms had simple jaws but not true teeth. Instead, their mouths contained bony structures used to crush or shear prey. Some Placoderms were up to 33 feet (10 meters) in length. Cartilaginous fish such as sharks and rays were common by the late Devonian. Devonian strata also contain the first fossil ammonites.
By the mid-Devonian, the fossil record shows evidence that there were two new groups of fish that had true bones, teeth, swim bladders and gills. The Ray-finned fish were the ancestors of most modern fish. Like modern fish, their paired pelvic and pectoral fins were supported by several long thin bones powered by muscles largely within the trunk. The Lobe-finned fish were more common during the Devonian than the Ray fins, but largely died out. (The coelacanth and a few species of lungfish are the only Lobe-finned fishes left today.) Lobe-finned fishes had fleshy pectoral and pelvic fins articulating to the shoulder or pelvis by a single bone (humerus or femur), which was powered by muscles within the fin itself. Some species were capable of breathing air through spiracles in the skull. Lobe-finned fishes are the accepted ancestors of all tetrapods.
The Devonian Period was a time of extensive reef building in the shallow water that surrounded each continent and separated Gondwana from Euramerica. Reef ecosystems contained numerous brachiopods, still numerous trilobites, tabulate and horn corals. Placoderms (the armored fishes) underwent wide diversification and became the dominant marine predators. Placoderms had simple jaws but not true teeth. Instead, their mouths contained bony structures used to crush or shear prey. Some Placoderms were up to 33 feet (10 meters) in length. Cartilaginous fish such as sharks and rays were common by the late Devonian. Devonian strata also contain the first fossil ammonites.
By the mid-Devonian, the fossil record shows evidence that there were two new groups of fish that had true bones, teeth, swim bladders and gills. The Ray-finned fish were the ancestors of most modern fish. Like modern fish, their paired pelvic and pectoral fins were supported by several long thin bones powered by muscles largely within the trunk. The Lobe-finned fish were more common during the Devonian than the Ray fins, but largely died out. (The coelacanth and a few species of lungfish are the only Lobe-finned fishes left today.) Lobe-finned fishes had fleshy pectoral and pelvic fins articulating to the shoulder or pelvis by a single bone (humerus or femur), which was powered by muscles within the fin itself. Some species were capable of breathing air through spiracles in the skull. Lobe-finned fishes are the accepted ancestors of all tetrapods.
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