To evaluate insect extinction in the fossil record, two other metrics need to be considered: total diversity and origination (Figs. 3 and 4b). Origination is a tally of the numbers of first appearances of taxa of interest in the fossil insect record for a particular time unit; essentially it is the inverse of extinction, which is a tally of their disappearances. Total diversity is a count of all known insect families occurring at a particular time; it provides the secular trend of increase or decrease of taxa during geologic time.