Progenitors
A Progenitor isn't much of a special things.
World Races and Progenitors are almost the same, just tgat Progenitors are the first on that planet therefore they've not been accepted yet.
They are also the ones with the first racial skills.
....
A primogenitor(2), and a Progenitor (1) aren't the same, (1) is the very first, (2) is if the race is facing an extinction Crisis, and only 2 or more remain. Note (2) only appears if it is only after 100s of years that that race reappears with up to 5 remnants