The chart shows the relative numbers of species in four groups of vertebrates over time. The chart is divided in three columns as era, period, and number of species. The first era is Cenozoic with recent and paleogene periods. The second era is Mesozoic with the cretaceous, Jurassic, and Triassic periods. The third era is called as Paleozoic with Permian, carboniferous, Devonian, Silurian, and Ordovician periods. The species of vertebrates are shown as bony fishes, archosours, birds, and mammals.