hitherto unknown ...

First of all, I think you mean: "unprecedented" and yes, I would say (at the risk of being blasted by everyone who comes in here) that "hitherto unknown" is the same as "unprecedented"

unprecedented: without previous instance; never before known or experienced; unexampled or unparalleled: an unprecedented event.

hitherto: up to this time; until now: a fact hitherto unknown.

Both from Dictionary.com, if you want to check for yourself, or for next time.