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See also: Pre-Cambrian
Precambrian (not comparable)
before the Phanerozoic
- (geology) The eon (or supereon) and rock formations dated before 541.0±1.0 million years ago, coinciding with the first appearance of the fossils of hard-shelled animals.
- The International Commission on Stratigraphy, which attempts to standardize the vocabulary of the field, is revising the boundaries between time periods based on physical-science methods rather than the kinds of fossils present.
- The boundary between the Precambrian and the Phanerozoic has been changed from time to time and will be subject to change, as will the eons listed as Hyponyms below.
- (geological eon): Cryptozoic (archaic)
- (geological eon): Phanerozoic