X-MEN #18

"Betrayal in the Bermuda Triangle, Part Three" Guest-Starring the FF! The X-Men and the FF have gone through a portal in the Bermuda Triangle and are stuck in a strange land complete with Dinosaurs, Mayan Temples
and strange snake people! It’s up to Reed Richards and Dr. Nemesis to get our crew back home, which isn’t the problem
as they are two of the biggest brains in the Marvel U. The problem is that a portal to our world is exactly what the evil forces of this land want! — Description from Comic Vine community (comicvine.gamespot.com).