What happens when a parallel world starts out different from our own but, through random chance and development, begins to resemble our Earth more and more closely? And what happens when those two universes begin to merge not just in style, but literally? It's a fascinating scientific question that the Fantastic Four will have to consider as they swap places with their counterparts in this other world and find themselves battling for survival in the universe where everyone is a dinosaur, and not anthropomorphic ones, but literal full-scale dinosaurs with all their super-powers, wearing amazing super-hero costumes! Can Sue Storm defeat Brachiosaurus Iron Man? Can the Human Torch take down Lambeosaurus Captain Marvel, her head frill mimicking her human counterpart's spiked hair? Can Reed Richards ever stop Quetzalcoatlus Black Widow, the deadly assassin of the skies? Beyond the dinosaurs and chaos and two universes merging, this issue also features emotional and heartfelt reunions with some missing members of the Fantastic Four family! So: Dinosaurs and catharsis, together at last. Plus: Sue Storm's doctorate is finally revealed!