A one-of-a-kind Tyrannosaur fossil helps explain why these predators ruled the top of the food chain

• Tyrannosaurs were some of the most formidable predators of their time, known to eat large herbivores.
• Researchers found the well-preserved remains of bird-like dinosaurs inside a tyrannosaur's stomach.
• The discovery suggests that tyrannosaurs' diets changed as they grew, which helped them become apex predators.

A 75-million-year-old fossil of a juvenile tyrannosaur helps explain why the apex predators ruled the food chain, new research shows.