Stratigraphically, the boundary between this period and the period precedin
Stratigraphically, the boundary between this period and the period preceding it is marked by appearance of dictyonemid graptolites, and Dobs Linn in southern Scotland is the type locality for that boundary. This period sees the first appearance of the jawless pteraspidomorphs, as well as fossils of the animal phylum Bryozoa. Its epochs include the Ashgillian and the Caradocian, which make up its "Late" subdivision. It saw Gondwana come to rest at the South Pole and the second-largest mass extinction in the history of the world, killing a third of all brachiopod and bryozoan families. It was named after a site in Wales by Charles Lapworth, and featured evidence of the first land organisms. For 10 points, identify this period followed by the Silurian and preceded by the Cambrian, the second period of the Paleozoic Era.
Stratigraphically, the boundary between this period and the period preceding it is marked by appearance of dictyonemid graptolites, and Dobs Linn in southern Scotland is the type locality for that boundary.
Ordovician Period