Who knows what creatures lived and died without fossil record. Believers of the TOE would have us believe that there are an infinite number of transitional beings that have no presence in the fossil record.
As for creatures mentioned in other cultures we have the Kraken, Griffin ( my high school animal ), Mermaids, Centaur, Pegasus, and the list goes on.
The Bible mentions the leviathan, Satyrs, Lion Men, dragons, the behemoth, and, now, news to me, I don't know why I never saw it before, the Unicorn.
Do we have any other evidence of these? What context was used to mention them?
Do I believe in the mythical one horned horse? No, not at this time and I don't really have any desire to research it.
We are told that "all flesh was corrupted" at the time before the flood. We are told that Noah was "perfect in his generations" that, in my opinion, depicts that his DNA was still 100% human. Who knows what other monsters could have been created by the genetic manipulation carried out on the animals and humans of that time by the fallen angels and the Nephilim?
However, if someone tells me that "if you believe scripture is literal, you must believe in a mythical horse with one horn" I will tell them that there are other possibilities for what the term "unicorn" is intended to describe.
If the poster who stated "Yeah, I got that. So you believe in unicorns, right?" in direct response to me stating that I take the bible literally, did not intend it to be a dig, an insult and a form of condescension, I must take their word for it. Maybe I was too sensitive. However, in the context that it was written, I believe it could have been taken either way.