In the paleontology of Old Earth, the Devonian is the time between approximately 416 to 359 million years ago; the period of the Paleozoic Era between the end of the Silurian and the beginning of the Carboniferous. More generally and informally, any gardenworld or hab space that seems similar in the array of plant and animal species might be referred to as "Devonian".
During most of the Devonian, the planet was warmer than at present, with extensive epicontinental seas. The atmosphere contained less than three quarters of the oxygen that it does in the modern age, but carbon dioxide was eight times more abundant. The primary continents were Euramerica, at the equator, consisting of what would later be Europe and North America, a small northern landmass consisting of the future Siberia, and Gondwana, consisting of most of the other later land masses, in the southern hemisphere. The Devonian is well known as the period during which life on land first flourished in a significant way, with the advent of the first forests and seed-bearing plants, the first true soils, and the first tetrapods as well as a major radiation of land-borne arthropods including the first insects. In the water, there were early radiations of the jawed bony fishes and of sharks, so much so that the Devonian has sometimes been called "The Age of Fishes" in popular works. There were great reefs, though these were formed primarily by calcareous algae and stromatoporoids; the corals of the day were less important.
There are relatively few re-creations of Devonian landscapes and biota in the Terragen Sphere today. Unlike the case for some later periods, no whole planets are "Devonian", and even the lazurogened biota from this period are not particularly common relative to those of later ages. This is in part because authentic reconstructions are more difficult for such ancient organisms, some of which have left incomplete fossils or have no clear living relatives, and in part because there are fewer spectacular specimens from this period than from the Carboniferous and later periods. An exception to this general rule is an occasional fad for some of the more baroque placoderms, and especially for spectacularly gigantic species such as the arthrodires.