The full form of CREO is Committee on Recently Extinct Organisms.

CREO (Committee on Recently Extinct Organisms) has developed standardized criteria for analyzing extinctions that can be applied across diverse taxonomic groups. CREO are now in the process of organising an effort to collect extinction data and analyze them against these criteria so that an accurate and comprehensive survey of recent extinctions can be produced. This research program will result in a comprehensive database of extinction information; and the data gathered from this effort can be used in a number of important conservation applications

The total number of known extinct species is 905 species. Most of them occurred during the 1900s (see charts below). The starting date for the inclusion of extinctions into the charts was set at 1500 AD to be in line with the starting date used by the Committee on Recently Extinct Organisms. Estimate of the number of species is still unknown , ranging from three to ten million to the tens of millions, and many of them have been lost forever without being noticed by science. Therefore, the extinction rate may also be underestimated.