Fig. 7 in The fossil record of early tetrapods: Worker effort and the end-Permian mass extinction

Fig. 7. Species discovery curves for several groups of fossil organisms show substantial differences in form. All discovery curves are shown as percentages, even though final totals, in 2003, are very different: trilobites (n = 4126), early tetrapods (n = 515), dinosaurs (n = 694), fossil birds (n = 221), and fossil mammals of North America (n = 3340). The horizontal line marks the "half life" of the discovery curve, the date by which half the currently valid taxa had accumulated. Data from these sources: trilobites (Tarver et al. 2007), dinosaurs (Benton 2008), fossil birds (Fountaine et al. 2008), fossil mammals (Alroy 2002).