See now, I always thought that the existence of fossils of strange forms of animals no longer in existence, at high altitudes in folded rock formations in the mountains, was more of a problem for young-earth creationism. Indeed it was just that sort of thing that made the idea of a young earth increasingly untenable to thinking people in the 19th century.
I don’t know why you would think that. Once you have postulated a world-wide flood, accompanied by cataclysmic shifts in rock formations, you can pretty much explain any fossils anywhere.
Plus, once you have postulated a creative God, that God can create anything, including things which will tend to give the unchosen a way to justify their unbelief.