Arlo Smith

When the Devonian period started about 416 m.y.a, the planet was changing and the contenent of Gondwana was moving upward, away from the South Pole, and a continent began to form neer the Equator. Known as Euramerica, it was made with a combination of North America, northern Europe, Russia, and Greenland.
The Devonian, otherwise known as the Age of Fishes, as it spawned a large variety of fish. The most powerful of them were the armored placoderms, a spiecies that first showed up during the Silurian. With powerful jaws lined with blade-like plates like teeth placoderms fed on mollusks and other invertebrates, but later species evolved into, large creatures measuring up to 33 feet long. Other types of plated fish that lacked jaws developed a variety of forms. Fossil specimens include species with horseshoe-shaped heads and others that looked like shields.
Despite their heavy protection, these primitive fishes weren't built to live long. The Devonian ancestors of fishes living today belonged to two main nonarmored groups. The cartilaginous fish, their called that because cartilage formed their skeletons, later gave rise to sharks and rays. They had small, rough scales, non bendy 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 with 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 animals come from the rocks of Devon.
quotes from tp://www.ucmp.berkeley.edu/devonian/devonian.php"


Trilobite:  Terataspis grandis - paper sculpture - paleoart
Trilobite: Terataspis grandis - paper sculpture - paleoart

bony fish



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spiky fish
http://paleobiology.si.edu/geotime/main/htmlversion/devonian2.html





Lesson 31: OverviewLesson 32: Late Devonian Extinction EventLesson 33: FishLesson 34: Land PlantsLessson 35: Species In-Depth - AmmonitesTest
Devonian Fast Facts


Started: 416.0 Ma
Ended: 359.2 Ma
Duration: 56.8 Million Years
Preceded By: Silurian Period
Followed By: Carboniferous Period
Paleoclimate



Mean atmospheric O2content over period duration
ca. 15 Vol %
(75 % of modern level)

Mean atmospheric CO2content over period duration
ca. 2200 ppm
(8 times pre-industrial level)

Mean surface temperature over period duration
ca. 20 °C
(6 °C above modern level)

Sea level (above present day)
About 180m, gradually falling to 120m through period




































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