This rapid appearance of many plant groups and growth forms has been referred to as the Devonian Explosion or the Silurian-Devonian Terrestrial Revolution.[55]. The extinction began roughly 380 million years ago, midway through the segment of . The paleoequator (the site of the Equator at a point in the geological past) passed through North America and through China, which was at that time a separate landmass. [27][28], Sea levels were high worldwide, and much of the land lay under shallow seas, where tropical reef organisms lived. The former killed off coral reefs, jawless fish, and trilobites, while the latter caused early ammonites and placoderms to die off. The largest continent, Gondwana, was located entirely within the Southern Hemisphere. The Devonian Period was a time of great tectonic activity, as the major continents of Laurussia and Gondwana drew closer together. Sea levels were exceptionally high during the Devonian, giving a widespread relatively warm and equable climate for most of the Period. is the number of genera living in a period that did not survive that period. [54] These are the oldest-known trees of the world's first forests. Two snails are displayed: the slipper shapedPlatyceras carinatumandPlatyceras rarispinum. However, unlike the four other great extinction events, the Devonian extinction appears to have been a prolonged crisis composed of multiple events over the last 20 million years of the Period. Two specimens ofPseudoatrypa devoniana, shown from different viewpoints, are excellent examples of pyrite replacement, Moss Animals (ToL: Bryozoa

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