Tyrannosaurus rex
Reborn as Tyrannosaurus rex, you would spend your teens gaining weight at a frightening pace and your adulthood as the largest predator in your corner of the world. Enjoy it while it lasts – few of you made it past thirty.
Laramidia, 68 million years ago
Your home is Laramidia, the western half of a North America split by a shallow inland sea. It is warm, green and full of rivers, floodplain forests and herds of Edmontosaurus and Triceratops. You live in the last two or three million years of the age of dinosaurs; the asteroid that ends it all arrives about 66 million years ago.
An adult of your kind measures around 12 metres from snout to tail and is usually estimated at 6–9 tonnes. The famous arms are about a metre long – short, but heavily muscled, and their real purpose is still argued over. You are not alone at the top of the food chain for long, though: young tyrannosaurs, lighter and faster than their parents, probably hunted different prey, so a single species filled several predator roles as it grew up.
A nose, two eyes and a jaw like a bone crusher
Your brain has unusually large olfactory bulbs, so you smell carcasses and prey from far away. Your eyes face forward more than in most big theropods, giving you real depth perception. Then there is the bite: biomechanical estimates run to tens of thousands of newtons, enough to splinter bone, and fossil dung full of bone fragments shows you did exactly that.
A 2023 study argued that, like lizards, you probably had lips covering your teeth when your mouth was closed – less movie monster, more giant monitor. Skin impressions from adults show small scales; whether juveniles wore a fuzzy coat is still open.
Grow fast, die young
Growth rings in bones show tyrannosaurs put on several hundred kilograms a year during their teenage spurt and reached adult size in about two decades. The oldest individuals studied were in their late twenties to early thirties. Most deaths came earlier: injuries, infections and fights with your own kind left marks on many skeletons, including bite wounds to the face.
