Question: How do you know if a dinosaur from years and years ago is a meat eater or not?

Juan Carlos Lopez-Baez answered on 19 Mar 2014:

Great question @cookieninja12. That tends to be due to the shape of their teeth. Each animal has different teeth depending on the sort of food they eat (this has evolved over time). Meat eaters (like lions for example) tend to have very sharp teeth to eat meat, whilst herbivores (plant eaters) tend to have more flat teeth, to crush the leaves of plants and the bark. Omnivores (animals that eat everything, like us!) have a mixture of both.

Of course, there are other ways to tell too, as you can assume that certain bones (like the jaw or the claws) could be adapted to hunt and eat meat, but normally the teeth are the best tell-tale for it.