archaeozoic, a. [Gr. 'archai^os ancient + zw^,on animal.].
Like or belonging to the earliest forms of animal life. [1913 Webster]
formed in or belonging to the earlier of two divisions of the Precambrian era. [WordNet 1.5]
archaeozoic, n. [Gr. 'archai^os ancient + zw^,on animal.].
the time from 1.5 billion to 5 billion years ago; the time when the earth's crust formed; a time when only unicellular organisms and the earliest forms of life are present. [WordNet 1.5]