Tyrannosaurus rex is one of the most famous dinosaurs because it was enormous, powerful, and unusually well represented in the fossil record. It lived near the end of the Cretaceous Period, about 68 to 66 million years ago, in what is now western North America. Studying T. rex helps scientists understand predator biology, ancient ecosystems, and how fossils preserve clues about behavior.
Its skeleton shows a mix of extreme strength, specialized senses, and evolutionary adaptations for life as a large theropod.
Key Facts
- T. rex lived about 68 to 66 million years ago during the Late Cretaceous Period.
- Adult T. rex could reach about 12 to 13 m in length and stand about 3.5 to 4 m tall at the hips.
- Estimated adult mass was commonly about 6,000 to 9,000 kg, depending on the individual and model used.
- Speed can be estimated from trackways using v = d/t, but direct running speed for T. rex remains debated.
- Bite force estimates for T. rex are among the highest of any land animal, often modeled at over 30,000 N.
- Relative growth rate can be described by growth rate = change in mass/change in time.
Vocabulary
- Theropod
- A group of mostly meat-eating, two-legged dinosaurs that includes T. rex and modern birds.
- Fossil
- A preserved remain, impression, or trace of an ancient organism found in rock or sediment.
- Cretaceous Period
- The geologic period from about 145 to 66 million years ago, ending with the mass extinction that eliminated nonavian dinosaurs.
- Paleoecology
- The study of ancient ecosystems and how extinct organisms interacted with their environments.
- Bite force
- The amount of force produced by an animal's jaws when biting.
Common Mistakes to Avoid
- Calling T. rex a Jurassic dinosaur is wrong because it lived in the Late Cretaceous, tens of millions of years after the Jurassic Period ended.
- Assuming every large tooth means constant active hunting is wrong because teeth show diet and feeding ability, but behavior must be inferred from many lines of evidence.
- Drawing T. rex standing upright with its tail dragging is wrong because its body was balanced horizontally, with the tail held off the ground as a counterweight.
- Treating fossil reconstructions as exact photographs is wrong because scientists combine bones, comparisons with living animals, and models to make the best supported interpretation.
Practice Questions
- 1 A T. rex is estimated to be 12.4 m long. If a museum scale model is built at 1:20 scale, how long should the model be in meters?
- 2 A juvenile T. rex gained 4,800 kg over 12 years. What was its average mass growth rate in kg per year?
- 3 Explain why a split-view reconstruction showing both skeleton and muscles can teach more about T. rex biology than a skeleton alone.