These conservation status categories are used in Wikipedia articles.
For threatened species and species believed to have become extinct after 1500, the categories are based on the IUCN (International Union for Conservation of Nature and Natural Resources) Red List 1994 or 2001 categories. Such species should be classified using the IUCN criteria directly using the most up-to-date database; the criteria given here are only a summary.

IUCN3.1
IUCN2.3CITESAppendix I contains highly threatened species; most of these are assessed by IUCN or TNC too however.
Appendix II includes lesser-threatened and look-alike species; this status may be used for the former if no formal status evaluation by IUCN etc exists.
Appendix III does not include globally threatened species; "CITES_A3" is not to be used anymore.


TNCThese should only be used if they a) apply to the global population and b) if no global system has assessed the species yet.

EPBC
DEC's Declared Rare and Priority Flora List categories. (Western Australia)
DECFQLDNCANSWBCA
COSEWIC
ESA
NZTCSThe following additional categories cover species that fall outside the scope of the IUCN Red List. The IUCN criteria are authoritative and should be used directly if applicable.
It should be noted that scientific literature does not usually distinguish between fossil and subfossil specimens. Generally, if molecular analysis or radiocarbon dating can be routinely carried out on specimens of a taxon, the taxon is classified as "Prehistoric". The recent discoveries of what seems to be minute amounts of preserved soft tissue in some dinosaur specimens, on the other hand, would not alter their "Fossil" status. As a rule of thumb, taxa extinct in the recent 50–30.000 years would possibly qualify as "Prehistoric".
Please do not use a conservation status that has not been officially given by an authoritative source. Your own judgement may be considered original research, which is against Wikipedia policy to include.