Geochronologic abbreviations, in temporal order, from oldest to youngest, for this and the following figure are as follows (from Gradstein et al. 2004). The Paleozoic consists of the Devonian, Carboniferous and Permian; the Mesozoic consists of the Triassic, Jurassic, and Cretaceous; and the Cenozoic is the Paleogene and Neogene. The Mississippian and Pennsylvanian are subperiods of the Carboniferous Period. Some stages of short duration are listed below but not placed in Figures 3 and 4.