Wait a second. Why did dinosaurs have tails?

Question: Why does T. rex have such a big tail?

Answer: The tail is a counterbalance, so the body doesn’t come crashing down.

Everyone knows this is the right answer. All the books in the volunteer library say so. We’ve been telling kids this since 1907 (or thereabouts).

You can do an experiment. Go to the Museum Store. Buy a plastic T. rex. Cut off the tail with your Leatherman. Watch the plastic T. rex fall. See? Case closed.

Bakker - Tail Blog 1Dr. Bob does say that’s the right answer. But he also says it is the totally wrong answer.

Dang PhD! Doesn’t he know we have to talk to 35 fourth-graders all at once in our Fossil Hall? We need simple, direct answers, not some sort of Talmudic rumination that goes around in circles and ties itself in knots like a philosophical pretzel.

Wait. He does make a good point or two.

First point: Dino tails were made of live bone and thick muscle, tissue that’s expensive for any animal to make. To grow his massive tail, a rex would have to eat lots more protein and minerals than what he would need if he were tail-less. Any rex who could do away with his tail would save 35 percent of his total food bill.

If the only purpose of the tail is to be dead weight that balances the body in front of the hips, it seems silly to build the tail out of such costly material.

Second point: Consider the turkey. Or a free range chicken or ostrich. Or Texas roadrunner. They are just as bipedal as a tyrannosaur or allosaur but they have hardly any bone or muscle in their stubby little tails (tail feathers are very light and inexpensive).

Go out to a farm and chase chickens and turkeys. Come to Seymour and try to catch a roadrunner as it zig-zags between the cactus. You will discover that these nearly tail-less critters run around and maneuver quite efficiently — and hardly ever fall over on their beaks.

Bakker - Tail Blog 2If evolution can make a bird who balances perfectly without a heavy tail, why would Darwinian processes insist on giving dinosaurs such wasteful rear ends? Let’s walk through the history of tails to see how function shifted over the last 380 million years.

Stage One: The Earliest Amphibian, the First Vertebrate with Legs and Toes Fit for Walking.

We trust you’ve been watching “Your Inner Fish” on TV. Go read the book. It’s a great story about how the earliest four-legged fossils were dug in Greenland, stubby-limbed fellows named Icthyostega and Acanthostega. These species retained some very fishy features, like internal gills, tail fins designed for swimming, and heads that had no way to hear airborne sound waves. They did have thick, strong thigh bones (femora) with large joints for the hip socket and knee.

Bakker - Tail Blog 3On the back of the thigh bone is a bump where a major muscle attached — it is the “tail-thigh muscle”, or, if you’re a fossil geek, you can use the Latin caudo-femoralis. Reptiles today have that muscle, as do salamanders.

Next time you are in Grand Chenier, La., go to the Cajun restaurant and order gator tail. The big chunk of meat you are eating is the tail-thigh muscle. It’s immense. It attaches to the side of the tail bones and then runs forward to attach to that bump on the thigh bone.

(More fossil-jargon for paleo-nerds: muscle bumps on the thigh are labelled “trochanters”, and the tail-thigh muscle is hooked onto the “fourth trochanter.” No, I’m not going to explain the other three trochanters; if you must know, get Al Romer’s The Vertebrate Body).

When the tail-thigh muscle contracted in Ichthyostega , it pulled the hind limb back and pushed the body forward. In other words, the tail-thigh muscle was one of the main propulsive organs that let the earliest four-legged animals walk. Top speed wasn’t fast; more of a steady waddle.

Stage Two: Early Reptiles, about 300 million years ago.

Early reptilian legs were much longer than in the early amphibs, and the beasts were far more nimble. The tail-thigh muscle still was the No. 1 propulsive unit, pulling back on the fourth trochanter in every step. The end of the tail was very long and whip-like, so it could be used as a weapon to slap other reptiles or inquisitive amphibians who got too close.

Bakker - Tail Blog  4Stage Three: Land Crocs, Close Kin of Dinosaurs, about 210-250 million years ago.

A major upgrade in running equipment came in the Triassic with the evolution of land crocs (technical label: the “suchia,” from the Greek word for croc). Land crocs did include the direct ancestors of today’s water-loving crocodiles and alligators, plus a dazzling array of land-lubbers. Leg action was even stronger than in the earliest reptiles, and the tail-thigh muscle was of great size.

Footprints show that most types of land crocs walked on all fours. However, the hind limbs were much, much thicker and longer than the front, so the tail-thigh muscle was dominant in thrusting the animals forward, with only a little help from the forelimb.

Bakker - Tail Blog 5Land crocs filled the Middle and Late Triassic with a dynamic horde of adaptive variations — we have three examples in the Morian Hall of Paleontology. There were huge predators with heads over a yard long, armed with saw-edged fangs (Postosuchus), who used their hefty tail-thigh muscles to generate fast running speeds. And there were armor-plated plant-eaters (Desmatosuchus) who employed their tails to brace the forequarters when the up-turned snout was busy excavating roots and tubers. And there were immense fish-eaters with long snouts bristling with stabbing teeth up front and, in the rear, steak knife teeth for cutting prey (Smilosuchus and its cousin Rutiodon). These aquatic species developed deep, flat-sided tails that were useful for swooshing underwater, providing locomotion a la croc or a la gator.

Bakker - Tail Blog 6Here are two land crocs featured in our Fossil Hall. The spiky fellow is Desmatosuchus, an herbivore. The big-headed chap is Postosuchus, a predator. Both are common fossils in the Triassic Red Beds of Texas and adjacent New Mexico.

Bakker - Tail Blog 7And here’s Rutiodon, a land croc who modified the tail into a swimming organ. Our Smilosuchus is a close kin. The drawing is by the great S. W. Williston for his delightful book, Water Reptiles of the Past and Present. Williston did all his own illustrations — my hero!

Stage Four: Carnivorous Dinosaurs, about 200 million years ago.  

The first genuine dinos evolved from a quadrupedal ancestor shaped like a Land Croc. The dinos took the trends in limb evolution to extremes. They reduced the size of the front legs even more, and increased the length and thickness of the hind. Voila! The early meat-eating dinosaurs were completely, unapologetically bipedal. Since the tail was already very heavy, it found employment balancing the forequarters.

My old professor Stephen J. Gould would label this event as an “exaptation.” That’s when an organ first evolves to fulfill some initial function — in this case, the tail-thigh muscle developed to power the hind limb stroke — and then, later, turns out to be useful in a new role: balancing.

Bakker - Tail Blog 8See! The long tail of bipedal dinosaurs did NOT first evolve as a counterbalance.

It first evolved in strictly quadrupedal animals, the earliest fishy-oid amphibian. The tail was the attachment for the tail-thigh muscle, a key unit of the hind limb stroke. The tail remained very important in walking and running in early reptiles and then in the close kin of dino ancestors, the quadrupedal land crocs. The first dinos were similar to land crocs except the hind legs were bigger and the fore legs smaller. Since they already had a super-heavy tail, the dinos were equipped to shift into a strictly bipedal style.

Yes, the T. rex tail served as a counterbalance. But all through the evolution of rex ancestors, going back to 380 million years ago, the tail’s main purpose had been as an attachment site for the super-sized tail-thigh muscle.

Where Night at the Museum Goes Wrong. And Black Labs Go Right.

I love the Night at the Museum movie, especially the T. rex skeleton that comes to life. However … the rex does illegal things. He wags his tail like a dinosaurian bloodhound or Labrador retriever.

Wrong. Since the tail-thigh muscle was thick and attached to the thigh, rex-like dinos couldn’t twitch, flip, wag or otherwise wiggle their tail with quick movements. Crocs and lizards have the same limitation: powerful sweeps of the tail are fine, but twitchy movements are impossible.

That’s why pet gators don’t wag their tails — even if you throw them a frisbee.

Bakker - Tail Blog 9Hmmmmmmm … that brings up a mystery. We mammals evolved from an ancestor very close to Dimetrodon, the fin-back reptile of some 285 million years ago. D’dons had thigh bones with huge fourth trochanters, where the tail-thigh muscle attached. And that means the tail was linked to the hind limb and incapable of rear-end wiggle-ness.

Modern mammals are weird. None of us has any connection between a tail muscle and the thigh bone, not even big-tailed species like otters, platypuses, pangolins * or giant red kangaroos. Somewhere between Dimetrodon and the earliest true mammal of the Triassic, our ancestors lost the thigh-tail linkage.

How can we tell when it happened? And how can we tell why it happened? It’s not a rhetorical question — I don’t know for sure. No one does. But I do have a hunch …

Bakker - Tail Blog 10*Don’t know what a pangolin is? “Scaly anteater” is another common name. Google it.

Forty years after Dipsy’s unveiling, original welder John Barber is back to watch her disassembly

There’s no sweeter story than that of a boy and his … dinosaur?

In February of 1973, 24-year-old John Barber was just out of art school in Virginia, having barely missed the draft and with no idea what to do with himself. He was visiting an aunt and uncle in Houston when he paid a visit to the Houston Museum of Natural Science — and happened upon a scene that would change his life.

“There was a large wooden platform raked at an angle, and a lot of large bones laid out in some kind of order. I walked around it a couple of times and realized that they were apparently going to assemble a big dinosaur,” Barber says. “I thought, holy cow!”

Having earned a fine arts degree in sculpture — and worked his way through school as a welder — Barber asked to speak to then-curator Dwayne Hicks to see if he might make himself useful. They reviewed his skills and 20 minutes later, Barber, now 64, left with a job.

Barber estimates he was making about $525 a month in those days. “I arrived in Houston with a small valise, a box of Magic Markers and a cardboard tube of drawing paper.”

Forty years later, Barber is back at HMNS supervising Dipsy’s de-installation. He paused to chat with us about his own history with Houston’s best-loved dinosaur and how it feels to see her come down.

Twenty years after their first meeting, John Barber is back to bid farewell to Dipsy
Barber poses with Dipsy during her de-installation

When Barber first began work on Dipsy’s armature, 18 months of bone preparation had already been completed. For non-sculptors, an “armature” refers to the steel support that, in this case, took the place of cartilage and muscles that would have supported Dipsy’s skeleton in life. The objective, Barber says, was to make the support as unobtrusive as possible so the public would view the maximum amount of dinosaur bone and minimum steel support. His mentor, Dr. Wann Langston, used to joke, “If you do your work right, no one will ever see it.”

By 1975, Dipsy was revealed to the general public.

via Pinterest

“We worked on that mount for almost two years,” Barber says. “Some people got upset that it took so long, but Dr. Langston was old school. His main interest in the mount was the feet. The reason our Diplodocus is mounted moving up a slope has to do with how the feet and legs were able to support that 30-ton mass going up a grade.”

via Pinterest

In life, Dipsy would have weighed the equivalent of two tractor trailers stacked on top of one another. Even her skeleton is heavy enough that it required 250-pound, 8-inch I-beams for support, laid across two pieces of railroad track that are concealed in her base.

Barber remained in the Museum exhibit business — and in Houston — for the next 25 years, only more recently deciding to devote his full attention back to (more traditional) sculpture. His sheet metal sculptures of Gulf Coast wildlife are shown at galleries throughout the region and online at johnbarber.com.

“As we approach the task of disassembling the Diplodocus some 40 years since I started working on it, I find myself contemplating the issue of time — how 40 years is the working life of a man, but for a fossil specimen is but a moment. I feel that I have an obligation to that specimen; it changed the course of my life in a profound manner, and brought me into a line of work that I found artistically fulfilling and intellectually satisfying. How much more can a man ask for in life?”

Have your own special memory of Dipsy? Post it here in the comments or share it with us on Facebook!

Help us help you: Name our new paleontological pal and win a guided tour of the new Hall of Paleontology!

By now you all should be acquainted with our new mascot:

T-Rex Trying to fit in!

He’ll be hanging out with us for the indefinite future, and it occurred to us that it might be polite to give him a name.

Well, that hasn’t gone smoothly, as you might imagine. In fact, the entire process reminds me of the infamous family shutout of ’92, when my sister was incubating and my two name suggestions — Maleficent for a girl, Pooch Patrol for a boy, naturally — were vetoed without so much as a vote.

Although in hindsight I think “Annie” does have a nicer ring, I’m dedicated to making this naming exercise a touch more fair. And that’s where you guys come in!

Here are the contest details: Leave a comment either here or on HMNS’ Facebook page with your suggestion of a name for our new spokes-dino. The top five submissions (read: our most favorite) will be selected by our online team, and then put to a vote on Facebook. The winner will get a guided tour for four of the new Hall of Paleontology — with more than 3 billion years and hundreds of species to cover, don’t you think you want a docent?

The power of social media is yours to harness, so use it!

The name nomination contest ends Friday at 5 p.m., so get your thinking caps on and come up with something our tireless T. rex can be proud of — just don’t ask him for a high five.

Wyrex’s fancy footwork and tender hands: Get to know this tyrannosaur’s softer side

As we all know, Tyrannosaurus rex is the world’s No. 1 favorite dinosaur, so we at the Houston Museum of Natural Science are as pleased as punch over our specimen Wyrex, a truly splendid fossil that will help fill out the Cretaceous zone of the new Hall of Paleontology.

Wyrex will join our casts of Stan, an adult rex, and Bucky, a teenage Tyrannosaurus, in the new hall next week.

Bakker Wyrex Blog
Here’s our Wyrex sniffing at the trail of our duck-billed dinosaurs

Our Wyrex gets its name for Montana rancher Don Wyrick, who spotted bones eroding out of river sediments that were deposited about 66 million years ago during the Lancian Age — the last slice of dinosaur history before the great die-off.

Of course, T. rexes are famous for their bone-crushing bite and the old question of whether they were cowardly scavengers or fearless predators. But equally fascinating is the century-old puzzle of tyrannosaur digits. (Fingers, not phone numbers).

And that’s precisely why our Wyrex is a scientific groundbreaker. He has the best-preserved hands and feet of any T. rex ever uncovered, and he has something to say about three tyrannosaurian problems:

Theory No. 1: Some scientists say: T. rex was a waddling stumblebum, so slow that you could easily escape it at an amble.

Let’s look at the hard (fossilized) data.  Our database includes all the maxi-fauna today —  land creatures who grow to a ton or more. We find that slow walkers, like elephants, have short shins and very short ankles compared to their thigh length.  A charging African elephant, for example, hits 22 miles per hour. Faster large animals, such as rhinos (who get almost as heavy as elephants) are equipped with more length in shin and ankle. An angry white rhino easily surpasses 30 miles per hour.

Wyrex, in contrast, seems elegantly leggy — his shin and ankle are way, way longer compared to his thigh than the ratios we see in an elephant. Wyrex confirms what a dozen other T. rex skeletons have already told us: These giant dinos were built for speed. (Whether they were built for comfort, I’d guess no one was brave enough to find out.)

Bakker Wyrex Blog
A rhino, a fast big critter, next to a T. rex. Notice how long the shin and ankle are in the rex.

Here’s another way to test the slow-rex theory. Fast animals today — small, medium and large — have compact ankles. The long ankle bones, called “metapodials,” are tightly bound to each other so they make one strong unit. Slow walkers like elephants have loosely constructed metapodials that let the entire ankle spread out.  Check out our Wyrex’s ankle. Tight or loose?

TIGHT! There are three long ankle bones, and the inner and outer bones hug the middle bone so tightly that the whole ankle works as one bony unit. That is not an elephant-style spreading foot.

Our three rexes, Stan, Bucky and Wyrex, tell us most emphatically that their species were not slowpokes.

Theory No. 2:  Some scientists say that T. rex fingers were powerful meat hooks.

Wyrex’s hand is worth pondering. In the new hall you’ll be able to stand very close to the bones, so you can compare your arm and fingers to his. At first glance, the rex mitt does seem as strong as a grizzly bear’s. But wait … in nature, what matters is how strong your hand is compared to the rest of your body. Wyrex was 10 times as heavy as the average grizzly bear. That means the Wyrex arm is 10 times weaker relative to his body weight than the bear’s.

When we diagram a grizzly bear with the the proportions of Wyrex, the poor bear seems to have a ridiculously wussy arm:

Bakker Wyrex Blog
Check out the measly arms on this Grizzly bear proportioned like our Wyrex.

Now analyze the Wyrex claws. Are they as big and hooked as hand claws from earlier meat-eating dinos? Nope. Our Acro (Acrocanthosaurus) is a bit smaller in body weight than Wyrex but has much heavier, sharper and more hooked claws.  T. rex evolved from an ancestor shaped like Acrocanthosaurus, who evolved from something like the Jurassic megalosaurs. If claw strength really was important, why did evolution make the rex claws weaker?

Then there’s the famous two-fingered salute. Most dino carnivores had three strong fingers — thumb, index finger and middle finger. Allosaurs from the Jurassic are built that way, and so are the acrocanthosaurs from the Early Cretaceous. So are all the raptors. One example? Our cast of Deinonychus, the raptor who inspired Jurassic Park.

Wyrex has a near-perfect hand. But how many fingers does he have? Two — thumb and index. And the finger bones are far skinnier than what you see in an allosaur or an acro. All T. rexes and their close cousins, the gorgosaurs, were weakly two-fingered.

Bakker Wyrex Blog
A rex arm next to a Jurassic meat-eating megalosaur.

How and why did evolution clip off that third finger? Wyrex shows us. Stare at the outer side of the hand. You’ll see an ultra-thin bone crowded against the index finger. That’s a remnant of the third digit. It was retained because some major muscles attach to the base of the third finger, muscles that are needed to rotate the whole hand sideways.  Other rex specimens probably also had that remnant of the third finger, but lost the bone after death when scavengers nibbled away the muscles.

third finger
The thin remnant of Wyrex’s third finger

The muscle-attachment on the finger remnant tells us that some sideways movement was still important in Wyrex, but it was a delicate movement — not the brute action of a meat-hook.

Theory No. 3: In 1905 one famous scientist theorized that rex fingers were for gentle…tickling!?

It sounds weird at first. However, that scientist was none other than Professor Henry Fairfield Osborn, the New York paleontologist who found the first T. rex and gave the species its name. Osborn had great insights into extinct animals. He had museum-smarts AND zoo-smarts.  He was on the board of the Bronx Zoo, and he observed live animals. He knew that a giant predator needed more than powerful jaws for killing prey and long limbs for chasing it; predators needed a way to attract desirable mates so they could make healthy, desirable offspring.

The problem: If you are a 10,000-pound rex who can bite another dinosaur in half in one chomp, how do you express tender, romantic feelings?

The answer: Tickling. Many animals today use a small finger or toe to stroke their loved ones. Critters with fur or feathers spend much time grooming their friends and mates with delicate strokes of claw-tips. Grooming renews the bond between male and female, between parent and youngster, and between pack-mates in a hunting group.

It is a fun fantasy. Think of it: a young mated couple of rexes relaxing after a meal of duck-bill meat, stroking each other’s necks and muzzles, then petting their newly hatched chicks.

The fantasy becomes more believable if rexes had fur or feathers. Feathers have been found with many small and medium-sized meat-eating dinos, but up until 2012 no one had excavated a big tyrannosaur with feathery pelage.

But in the spring of that year, our Chinese colleagues announced an Early Cretaceous tyrannosaur fossilized with big sections of skin.  In the skin were tightly packed feathers — thin, kiwi-like feathers — up to a foot and a half long. The Chinese species was very similar to what the direct ancestor of later tyrannosaurs must have looked like.  The conclusion, then, is that Wyrex, too, probably had feathers.

So recent discoveries back up what Professor Osborn said over a century ago: T. rexes had a softer side — literally!

An aside — Osborn was not only a superb research scientist, but also a brilliant designer of public exhibits. He was the first to mix skeletons with beautiful murals and sculptures of the extinct beasts in their natural habitat. And he envisioned a fossil exhibition as a series of safaris back into deep time.

In other words, Osborn would have loved our new HMNS Hall of Paleontology — and you will, too.