The flip side to this question is, how did you get in a position, as someone capable of being CTO, to not have any shares in the company from the start? And the answer is probably that it's your first time as CTO, because I don't see any other answer than that to this situation.
Your best bet is to make some political moves to make ownership happen for you. Otherwise, sounds like you're in for a ride that you're not necessarily the driver for.