During the Silurian period the giant southern supercontinent arced upwards through a broad peninsula, formed by Antarctica and Australia, which straddled the equator. While there was no major volcanic activity at this time, the smaller landmasses of Laurentia, Baltica and Avalonia, composing what would become North America, steadily converged together. Proto Siberia formed a large and isolated island in a northern hemisphere dominated by the global ocean of Panthalassa. The climate was warm and relatively stable with high sea levels, and high levels of atmospheric carbon dioxide. The apex predators of the oceans were giant sea scorpions; trilobites, brachiopods, bryozoan, and crinoids were all abundant. Bony fish make their first appearance, while on land archaic millipedes and spider-like creatures emerged. Land surfaces near streams were carpeted with miniature moss forest, increasingly dotted with taller earlier vascular plants.
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