This article is a list of biological species, subspecies, and evolutionary significant units that are known to have become extinct during the Holocene, the current geologic epoch, ordered by their known or approximate date of disappearance from oldest to most recent. The following list is incomplete by necessity, since the majority of extinctions are thought to be undocumented, and for many others there isn't a definitive, widely accepted last, or most recent record. According to the species-area theory, the present rate of extinction may be up to 140,000 species per year.