Figure 7. Histogram showing the number of genera described in each decade from 1790s to the 1990s. Data are extracted from extensible markup language (XML) tagged descriptions from the Treatise on Invertebrate Paleontology, part H, Volume 2 (Williams et al., 2000), and hence only apply to a subset (277) of the total genera assigned to the phylum (>5000). Note that data for the 1990s are not complete.