This union of the paleo continents of Laurentia (comprising much of North America, Greenland, northwestern Ireland, Scotland, and the Chukotsk Peninsula of northeastern Russia) and Baltica (now most of northern Europe and Scandinavia) occurred near the beginning of the Devonian. Unauthorized use is prohibited. This is the last in a 10-part series arguing that fossils record the Earth's recolonisation after a mass extinction near the very beginning of history. The Devonian Period is a period of time on the geological time scale which started about 419 million years ago and ended approximately 360 million years ago. However, he particularly enjoys writing about animals, nature, and health. The cause of the extinction has been attributed to the global cooling of the climate and oxygen loss in the Devonian oceans. Lower jaw of Eastmanosteus pustulosus from the Middle Devonian of Wisconsin, Tooth of the lobe-finned fish Onychodus from the Middle Devonian of Wisconsin. The bacterial and algal mats were joined early in the period by primitive plants that created the first recognizable soils and harbored some arthropods like mites, scorpions and myriapods. Vascular Plants (ToL: Embryophytes [land plants]