Dinosaurs long dominated Earth's land ecosystems with a multitude of forms including plant-eating giants like Argentinosaurus, meat-eating brutes like Tyrannosaurus and weirdos like Therizinosaurus, with its Freddy Krueger-like claws.

Failure to find the oldest dinosaur fossils may be because the areas in which they first evolved are now generally hard to explore like the Amazon rainforest or the Sahara desert, closer to the equator and not the far south of the Southern Hemisphere as previously thought,