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The Devonian Period
Also known as, "The Age of Fish" the Devonian Period was a time where there were more developments in fish structure. The Devonian also saw the first appearance of a type of flora that reproduced with seeds rather than spores. -
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Reef Building
The Devonian Period was a time of reef building the Earth's waters. The creation of these reefs are contributed to sponges and corals that lived during this time period. Some of the world's largests reefs were created during this time period. Invertebraes were able to grow well. -
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Continental Changes
During the Devonian Period, North America and Europe had collided at one point. This landmass is called Euramerica. The collision also resulted in the creation of the Appalachian Mountain Range. Meanwhile, the landmasses of South America, India, Antarctica, Australia, and Africa made up Gondwana. Gondwana was a large landmass nearby to Euramerica. -
Decline of Ostracoderms
Near the beginning of the Devonian, ostracoderms experienced a decline in numbers. Ostracoderms were shell-skinned, jawless, and had an bony armor plating. They existed through the Ordivician and Devonian Periods. -
Lobe Finned Fish Develop
Lobe finned fish began to develop in the Early Devonian Period. They are one of the two known species of bony fish at the time. Their lobe fins would eventually evolve into other appendages. A specific group of these organisms were the precedent to the later tetrapod organisms. -
Climate Promotes Plant Growth
The climate of the Devonian Period was humid and warm; excellent conditions for plant growth. Plants no longer were restricted to stay near bodies of water. The humidity of the air allowed them to move farther and farther away. -
Ammonites Begin to Develop
Anarcestida, the first type of ammonite, begins to form. Ammonites lived from the Devonian Period up to the Cretaceous Period. They assisted in the creation of coral reefs. They are excellent index fossils. -
Appearance of Early Amphibians
Many of the lobe finned fish were able to evolve their fins to become arms and legs. They were able to move out of the water, but were still restricted from full exploration. They still needed water to stay alive. -
Use of Lungs
During the Devonian Period, there were times of hypoxia in certain bodies of water. When the water ran out of oxygen some fish, for example the Dipterus, had evolved enough to have lungs on the outside of their body. This allowed them to breathe, even out of the water. -
Sharks Begin to Evolve
Placoderms were thought to be the precedent to early sharks. These sharks received the cartilage skeletal system yet. It is believed that these early sharks had evolved over time to remove the armor plating placoderms had. -
Diversification of Placoderms
Placoderms, one of the earliest jawed fishes, began to develop in the the Silurian Period. They were, however, relatively simple and had very few groups with specific traits. By the Early Devonian, Placoderms started to become more and more complex. By the Middle Devonian, Placoderms had reached a peak level of diversity, about five or six different types. -
A Modern Tree
The Archaeopteris (progymnosperm) appeared during the Middle Devonian. The Archaeopteris is considered one of the first trees in the geologic time scale. It is also considered one of the first modern trees because it reproduced through the spreading of seeds instead of spores. -
Diversity of Chondrichthyes
Chondrichthyes began to appear in the Middle Devonian Period. Primarily, it was the early sharks who began to display the traits of a chonrdricthye. Closer to the Late Devonian, the chondrichthyes began to increase in numbers and diversity. The chondrichthyes' skeletal system was made mainly of cartilage. This organism served as the early precedent to sharks and rays. -
Appearance of Tetrapods
Tetrapods were four-legged vertebrae. They began to appear about 360 million years ago. Primitive tetrapods that originally lived in the water evolved over time and were eventually able to move onto land. They were the first vertebraed organism to be able to walk on land. -
Mass Marine Extinction
Near the end of the Devonian, a mass extinction occured that affected only marine life. The exact cause is unclear. This extinction led to the end of brachiopods, trilobites, all jawless fish, placoderms, conodonts, and acritarchs.