protero-

1.
a combining form meaning “earlier,” “before,” “former,” used in the formation of compound words:
proterotype.
Also, especially before a vowel, proter-.
Compare proto-.
Origin
< Greek, combining form representing próteros, comparative formed from pró; see pro-2
British Dictionary definitions for protero-

protero-

combining form
1.
anterior or former in time, place, order, etc: proterozoic
Word Origin
from Greek proteros fore
Word Origin and History for protero-

before vowels proter-, word-forming element meaning "former, earlier," from comb. form of Greek proteros "before, former, anterior," from PIE *pro-, from root *per- (1) "forward, through" (see per).