[Ed. note: Recently, a reader named Wyatt left a comment on the blog asking HMNS Curator of Paleontology Dr. Bob Bakker a few questions about dinosaurs for a high school paper. We thought we'd share the answers with everyone - as well as wish Wyatt luck with his paper.]

1) Which predatory dino was the largest?

photo credit: Scott Kinmartin

The longest probably were the North African spinosaurs or the Argentine giganotosaurs; both families pushed 50 feet.

But tyrannosaurs were chunkier – thicker neck and torso. So tyrannosaurs would be heavier for any given length. A 40 foot long tyrannosaur would be heavier than a 50 foot spinosaur.

Strongest bite was had by the tyrannosaurs – much wider across the back of the head than giganotosaurs or spinosaurs.

2)  Which would dominate?

That depends on the habitat, geography and geological time. Big tyrannosaurs didn’t live with spinosaurs or giganotosaurs. Tyrannosaurs are restricted to Mongolia, China and North America. Tyrannosaurs did live with many kinds of raptors – including Velociraptor, Bambiraptor, Dromaeosaurus, Saurornitholestes. 

All raptors are smaller than all Late Cretaceous tyrannosaurs. The smallest tyrannosaur is Nanotyrannus, Late Cretaceous of North America, about 1,000 pounds in weight. The biggest raptor of the time was only 100 pounds or so.

photo credit: matsuyuki

But…..there were many more raptors alive at one time than Nanotyrannus. Just like today – there are many more coyotes than grizzly bears. Raptors were too small to attack adult Triceratops or duck-bills. But tyrannosaurs were too big to capture small, nimble prey, such as furry mammals, birds, lizards, and little herbivorous dinosaurs like Parksosaurus.

Spinosaurs have teeth like those of big crocodiles and probably ate fish and ocean-going reptiles like sea-turtles. Even if spinosaurs and tyrannosaurs lived in the same spot, they would have eaten totally different food.

So, who is “dominant” depends on what sort of prey is being hunted.

3) How do we find out what a big predator ate and how it caught it’s food?

By careful comparison with the design of living animals and analysis of the habitat clues left in the rocks.

Example:  Tyrannosaurus rex.

Commonest prey animal in the same sediment: the duck-bill Edmontosaurus.

Could T. rex catch a duck-bill?  Some scientists say that T. rex was a stumble-bum, limited to a slow walk. They say that we could walk away from a charging T. rex.

Bio-mechanical test:  Among big animals today, faster animals have longer ankle bones (they’re called “metatarsals.”) Look at a lion and a cheetah. Both are cats. The cheetah is much faster. Check out the hind legs. Who has longer metatarsal ankle bones, compared to the thigh?

The cheetah does.

Now let’s compare a duck-bill with a T. rex. The hind legs are built to the same general bird-like plan. Who has longer metatarsal ankle bones?

The T. rex.  So we can conclude that a T. rex really could chase down a duckbill.

How could the duck-bill get away?  Here’s one theory: The abundance of turtle fossils, gators, crocs, and salamanders show that the habitat was warm, wet and supported dense thickets and woodlands.  A duck-bill didn’t have to run away. It could hide in tangled vegetation.