Fig. 2.

Examples of how a strategy of temporal banding might be used to standardize biological classifications for extant species (see text). Shown is the one-to-one correspondence possible between 17 standard taxonomic ranks in some modern versions of the Linnaean hierarchy (see ref. 29) and the temporal bands (Mya) for 17 traditionally recognized geological episodes (see ref. 30). In one temporal-banding proposal, current classifications and nomenclatures could be revised (perhaps drastically), such that each clade would be ranked and named strictly according to the temporal window in which it arose. Under a less drastic proposal (which I favor), current classifications and nomenclatures would be retained, but each existing taxonomic name would simply be appended with a time clip signifying the approximate date of that taxon's origination. Note that these temporal-banding proposals do not extend to species-level taxonomic assignments, where biological criteria, including reproductive isolation (regardless of a species' date of evolutionary origin), would continue to apply.