Flat-Footed Reptiles to High Stepping Chickens

Most scientists believe that birds evolved from small therapod dinosaurs. The key step was the development of feathers, turning animals that could walk or climb into animals that could fly. In today’s post, Dr. Bakker discusses the evolution of a key feature of Archaeopteryx, the first dinosaur to be discovered with preserved feathers.

Lizard Paws to Chicken Fingers

320 million years ago – the first reptiles evolve, the earliest vertebrates that can lay air-breathing eggs on land.  Legs are sprawling and flat-footed. The front paws have five fingers, all with claws.

250 million years ago – the first archosaurs evolve, the close kin of crocodiles and birds.  Legs are more upright but still flat-footed. The hands have only three claws. The outer two fingers are thin and claw-less.

225 million years ago – the first dinosaurs evolve. Legs are upright and the heel held high, off the ground. The outer two fingers are weak.

160 million years ago – the earliest raptor-like dinosaurs evolve. The outer fingers are gone. Hind-legs are used for running and ankles are tall and thin. The three clawed fingers are long. And there’s a swivel joint on the wrist to let the hand move quickly side-to-side.

150 million years agoArchaeopteryx evolves. Hind legs are like those of raptor-type dinosaurs. The hand is almost exactly like a raptor-dinosaur’s.

110 million years ago – the first modern-style birds evolve. Hind-legs have stiff ankle bones, all fused together. The wrist bones too are all fused together and no fingers have claws.

Want to know more about our current Archaeopteryx exhibit? Check out this article on PlanetEye Traveler.

Interested in learning more about paleontology? Check out our past blogs.

Which raptor turned into the first bird?

We get so many great questions through our blog, and every now and then we can turn those responses into a blog post. One our readers favorite posts is “What would YOU ask a paleontologist?”

Last week we got this question from kght2:

“Do all birds come from a specific raptor, or do they come from different species of raptor that are cousins and not ancestors. I wonder this because while all birds are similar, they don’t seem to be any more similar than different raptors I have seen, and while this isn’t great information, I have heard of many raptors likely having some from for feathers. Primarily i wonder if the consensus is that all birds came from a single species, or that they came from a family of species instead, and this answer would also have implications that people should know for any species or family of species?”

Dr. Bakker, curator of paleontology here at the museum wrote this in response:

Another darn good question.

Archaeopteryx was the first bird, back in the Late Jurassic. It’s got the complicated arrangement of feathers on its arm to fly like a pheasant today does. All other birds evolved from Archaeopteryx or something very like it

Deinonychus (read my blog about Deinonychus) is a famous raptor-dinosaurs who look very close in their bones to Archaeopteryx. The tiny Microraptor from China is closer still.  Thanks to the dinosaur specimens from Laoning, China, we know that all the raptor-type dinosaurs had feathers. (T. rex had feathers too – the tyrannosaur clan were clothed in a full pelt of fine kiwi-style plumage.) But Deinonychus and all the Laoning feathered dinosaurs are from the Early Cretaceous – that’s too late to be an Archaeopteryx ancestor.

We need a Jurassic raptor to be our Archaeopteryx ancestor.

We now have a few specimens from the end of the Jurassic. These are advanced raptor-like dinosaurs with long arms built like Archaeopteryx.

So….we’re getting close to discovering the one, single raptor-dinosaur who evolved into the first bird. It had to be in the Mid or Late Jurassic.

If you have any questions you would like to ask any of our bloggers or curators, send us an email at blogadmin@hmns.org.

Interested in learning more about dino-birds? Make sure to check out our next exhibition, Archaeopteryx: Icon of Evolution, opening April 23, 2010.

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.

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.