Could T. rex catch a duckbill? And other dino questions answered.

[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?

T-Rex Dinosaur
Creative Commons License 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.

Tyrannosaur
Creative Commons License 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.

Dino Derby: What was T. rex’ top speed?

How Fast was the T-rex?

Tyrannosaurus Rexstirs passions.  Adults get scared when they imagine a live T-rex chasing kids in a theme park. And kids get a thrill when they day-dream of having a T-rex as a pet.

We scientists get passionate too, we sometimes get so excited we yell at each other when we debate a  T-rex’s speed and hunting habits.

One PhD will start with: “T-rex was a slow-footed fumble-bum! And he didn’t kill anything – he just ate carcasses he found already dead!!”

Then a bunch of us will reply: “That’s just nuts!  Tyrannosaurus was faster than any big veggie-saur! And one bite could kill a duck-bill!”

Who’s right?

TOOLS & RULES.

We need tools – mathematical rules to tell us how fast an extinct animal could run and whether a meat-eater could catch his prey.

Lets take the CHEETAH versus LION.

First we need two critters, close relatives, who have very different top speeds. Lions and cheetahs are perfect. They’re both big cats and they have the same basic design in leg joints.

Cheetahs are way faster. Cheetahs hit nearly 70 mph in a sprint. Lions can’t go much faster than 40 mph.

LONG ANKLES.  Check out these two diagrams. Ok – where does the cheetah get its extra velocity?  From its ankles. Much of the high speed comes from longer ankle bones. The ankle length compared to the thigh length is a reliable speed index in close relatives.

That’s an old Rule that Darwin knew back in 1859.

T-REX versus DUCK-BILL

Duck-bills were the most common big veggie-saurs in the time of the T-rex. The question is, could a T-rex catch a duck-bill?

We need to measure ankles compared to thighs in a rex and a duck-bill of the same geological time zone. Duck-bills and T-rexes have basically the same style of hind legs. And the hind legs deliver all or almost all of their  forward thrust (Duck-bills did put their finger tips down on the ground while walking – but there wasn’t much weight on the forelimb.)

Check out diagram # 3. Here’s a T-rex with a thigh (femur) that’s 1200 mm long. And next to the T-rex is an Edmontosaurus, a big duck-bill.

Who has longer ankles?

THE T-REX!

The longest bones in the ankle are the metatarsals. And the rex has much longer metatarsals, compared to the duck-bill.

CONCLUSION:
T-REX COULD CATCH A DUCK-BILL EASILY, IN A SPRINT ON OPEN GROUND.

That’s cool.  But now we have more questions – how fast was a duck-bill and a T-rex, in mph?  And did a T-rex have the killing equipment necessary for bringing down live prey? Stay tuned for the answers to these questions.

Your Dino Mummy Questions, Answered

Ed. Note: Leonardo has only been on display in Dinosaur Mummy CSI: Cretaceous Science Investigation for a few weeks – but we’ve already gotten a ton of fascinating questions from visitors. In this post, Dr. Bakker  answers them. If you have a question about Leonardo – or anything on exhibit at the Houston Museum of Natural Science – send it to blogadmin@hmns.org and we’ll post the answer here.

Dinosaur Mummy CSI presents scans of Leonardo that show gut contents and even a possible heart. Does Leonardo have lungs preserved?

There are some curious iron concretions revealed by the x-rays here but nothing definite.

Duck-bill dinosaurs do not have hollowed-out bones of the sort we see in birds and raptors and tyrannosaurs. Therefore we don’t expect that they had the very small lungs and big air chambers in the body cavity characteristic of modern birds.

The lungs would be tucked up high in the chest, covered by rib numbers 3,4,5,6 – if the lungs were like those of birds and crocodiles.

The drawings of Leonardo in the exhibit are very colorful – how do you know what colors dinosaurs had on their skin?

…theoretical stripes.

Think “Okapi.” That’s the giraffe-like thing in wet woodlands today.

Dinosaurs had bird-style eyes, so camouflage had to match habitat colors. Dull browns and greys were not good enough to fool an eagle-eyed gorgosaur.

Early Judithian environs had wet forests with big conifer trees and, in the rainy season, thick underbrush. Dry season would bring browns & rust colors.

So……..Mike Berglund (a dinosaur illustrator) has made a testable theory with his partially banded Brachy. Breaking the profile by having the tail a different color would help flummox predators, who would have a more difficult time seeing the whole body and tail shape. The thick verticals would help the beast blend in among the tree trunks.

How can we test color ideas?  More paleo-environmental research. More thinking about fossil pollen, turtles, crocodiles & salamanders….all witnesses to rainfall, groundwater, and floral geometry.

What animals alive today would be most like Leonardo?

Eland
Creative Commons License photo credit: The Anti-ZIM

The Antelope Family – most diverse family of medium-large planteaters on land today. The Antelope Family includes cows and buffalo, gazelles and oryx, funny-faced hartebeest and gnu, cute duikers and stately eland. Muskoxen and sheep and goats. Antelope supply most of the prey for lions, leopards, cheetah and hyenas.

The Duckbill Family is the most diverse, big-ish plant-eaters in the last part of the dinosaurian age, the Late Cretaceous. The Duckbill Family includes our HMNS Edmontosaurus, and the Trombone Dinosaur, Parasaurolophus (kids’ favorite). And the “Good-Mother” Maiasaura, who left us fossil eggs and nests. Leo’s species, Brachylophosaurus, is a duckbill too. Duckbills supplied most of the prey for all the tyrannosaur meateaters, such as Gorgosaurus, Daspletosaurusand the famous Tyrannosaurus rex.

The technical name for the Antelope Family is Family Bovidae, or “bovids” for short.

The technical name for the Duck Bill Family is Family Hadrosauridae, or “hadrosaurs” for short.*

Want to learn more about Leonardo and other dinosaurs?
See how we moved the 6-ton fossil into the museum.
See David Temple repairing and gluing a fossil back together.
Draw a dinosaur with Dr. Bakker.