Smithsonian National Museum of Natural History Geologic Time The Story of a Changing Earth
Presented by the Department of Paleobiology.
The Devonian
Contents
Overview
Life in the Devonian Seas
Terrestrial Habitats Conquered
The Devonian Extinction
and Tectonics during the Devonian
Evidence
Leaf and wood of Archaeopteris.
learn more
sample
Placoderm
Ammonite
Shark
Brachiopods
Trilobites
Centipede
Lobe-finned fish
Amphibian skull
references and links
Foundational Concepts
Dating Methods
Earth Processes
Life Processes
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Life in the Devonian Seas
Invertebrate and plant life teemed in the vast ocean that covered much of the globe. Ammonoid cephalopods first appeared in the Early Devonian, along with siliceous sponges. Brachiopods (which arose in the Cambrian) reached their maximum diversity as did hundreds of rugose coral species. Extensive reef-building produced some of the largest reef complexes in Earth’s history. Trilobites are also known from this time, but most groups had disappeared by the end of the Devonian, leaving only a select few genera to continue on through the Carboniferous and Permian.

The first radiation of vertebrates with jaws (gnathostomes) occurred during the Devonian, which is why it is sometimes known as the “Age of Fishes.” Although they first appeared in the Silurian, spiny acanthodians and armored placoderms reached their peak diversity during the Devonian and began to dwindle in numbers later in the Paleozoic. Some, like the giant Dunkleosteus, reached nearly three meters in length and were menacing marine predators. Placoderms had no teeth, instead relying on self-sharpening bony plates in their jaws that performed the function of teeth. Chondrichthyan (cartilaginous) fishes, such as sharks, were Ordovician survivors that thrived during the Devonian. A few shark scales have been dated to the Late Ordovician, but the earliest shark teeth are Early Devonian, and the first relatively modern-looking sharks had evolved by the Middle Devonian. The first true bony fishes (osteichthyans) appear as well, as both lobe-finned (sarcopterygians) and ray-finned (actinopterygians) forms. The lobe-finned fish are of particular interest because they gave rise to the first land vertebrates, around 360 million years ago.




Overview | Life in the Devonian Seas | Terrestrial Habitats Conquered
The Devonian Extinction | Climate and Tectonics during the Devonian



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