Synonyms: Tertiary, Tertiary period
Definition: from 63 million to 2 million years ago
Similar words: period, geological period
Definition: a unit of geological time during which a system of rocks formed
Usage: ganoid fishes swarmed during the earlier geological periods
Synonyms: 3rd, tertiary, third
Definition: coming next after the second and just before the fourth in position
Similar words: ordinal
Definition: being or denoting a numerical order in a series
Usage: ordinal numbers; held an ordinal rank of seventh