Fish-like vertebrates appeared toward the end of the Ordovician. A mass extinction, which may have been the second largest recorded by the fossil record, ended the Ordovician. It may have been caused by global cooling and glaciation. The went extinct at the end of the Permian. First fossil gnathostomes are from the early Silurian, but may have branched from agnathans in the Cambrian.
First bryophytes appear in the record in late Devonian, but probably evolved earlier.
Gondwanaland existed in the south, and several smaller continents in the north. Tropical climate except in polar regions, where glaciers existed. Extensive swamp forests of horsetail and clubmoss trees, and lots of ferns and tree ferns. Pollen freed the plants from the requirement of water for swimming gametes. This was an important development for the expansion of plants on earth.