But here’s the Hitch: Who really discovered that dinosaurs had feathers?

I grew up in the 1950s and 1960s reading books about the dinosaur “orthodoxy.” According to this traditional view, the dinos died out at the end of the Cretaceous because their beloved swamps dried up and the air became too cool. But the new conditions were perfect for us quick-thinking Mammalia, so we took over, along with the other hot-blooded class, feathered birds. That was the Official Scientific View until the 1970s.

Whew! It’s hard to believe that four decades ago paleontology could be so very, very wrong.

Us versus Them. The smart hot-blooded mammal Didelphodon defies a rex. The furball is saying “Just wait till yer swamps freeze....”

Us versus Them. The smart hot-blooded mammal Didelphodon defies a
rex. The furball is saying “Just wait till yer swamps freeze…”

Today we know that Tyrannosaurus rex was not a big lizard. It was the 10,000-pound roadrunner from hell, clothed in fine feathers. Tyrannosaurs and other dino-clans ranged far north and far south and survived icy winters just fine. We mammals were kept small all through Mesozoic times because the dinos, on average, were faster on their feet, quicker in their jaws, and had better hearts and lungs. Dinos won the roles of top predator and top herbivore fair and square. The humiliating truth is that we mammals are the class that won by default, taking over only because some external event removed our dinosaurian overlords.

Face the facts friends: we are furry carpet-baggers.

Question: Who first discovered that dinosaurs were part of the hot-blooded bird family tree?

Was it Dr. Bob Bakker, your faithful curator? Aww, nice of you to ask, but the original hot-blooded-dino guy was long before my time.

How ‘bout Yale’s John Ostrom, who dug up the raptor Deinonychus in 1964 and linked raptor-dinos to the early bird Archaeopteryx?

No, he wasn’t the first. (Oddly, John fought the idea that Deinonychus had feathers.)

Was the first dino-bird chap Thomas Henry Huxley, the pugnacious defender of Darwin in the late 1860s and 1870s? Huxley, who coined the term “agnostic,” was a favorite of my advisor at Harvard, Stephen J. Gould. Huxley did point out that hips and shoulders of dinos were very bird-like, and so were feet. Therefore, Huxley argued, some sort of dinosaur-oid was the ultimate ancestor of the bird class.

But no again. Huxley was not the first to see bird-ness in the dinosaurs.

T. H. Huxley, as portrayed in Punch. Among his many jobs, Huxley served on the Board of Fisheries.

T. H. Huxley, as portrayed in Punch. Among his many jobs, Huxley
served on the Board of Fisheries.

Got your notebook ready? Here comes the answer, and it makes most museum-goers raise an eyebrow.

The true discoverer of feathered dinos was… the Reverend Edward Hitchcock, State Geologist of Massachusetts, Professor at Amherst College, philosopher and Congregationalist pastor. Hitchcock figured out that dinos were a subclass of birds as early as 1838 — four years before the term “dinosauria” was invented!

First Director, Massachusetts Geological Society, Edward Hitchcock. His wry sense of humor and boundless joy in science is evident.

First Director of the Massachusetts Geological Society, Edward Hitchcock. His
wry sense of humor and boundless joy in science is evident.

How many skeletons did Hitchcock dig up? None. Not a one. But surely his lab got many well-preserved parts of dinos, right? Nope. Only after he retired did a partial skeleton show up, blown to bits by gunpowder used to excavate a well. Hitchcock came to the fundamental truth about dinosaurs entirely from fossil trackways.

Across the pond at Oxford, Hitchcock’s colleague, the Reverend William Buckland did dig hundreds of Jurassic and Cretaceous bones and some pretty good skeletons. The Oxford fossils inspired Buckland’s student, Richard Owen, to come up with the name “dinosaur” in 1842.

Sad to say, neither Buckland nor Owen realized that their restorations of dino skeletons were, in today’s parlance, “bass ackwards” — they put a huge bone in the shoulder, giving the critters a clumsy muscle-bound look in the forequarters. They didn’t realize that their “shoulder” was really part of the hips. Hitch*, on the other hand, without a single well-preserved osseous specimen, scrutinized the footprints and got dinos correct, fore and aft.

What a guy.

“Bass Ackward” dinosaur in the 1820‘s--1860’s. The restoration done under Richard Owen, with gigantically distorted forelimbs and flat feet. Painting by Luis Ray from our “Big Golden Book of Dinosaurs”.

“Bass ackward” dinosaur in the 1820s-1860s. The restoration done
under Richard Owen, with gigantically distorted forelimbs and flat feet.
Painting by Luis Rey from our Big Golden Book of Dinosaurs.

Hitchcock and Buckland were members of the “Pious Paleontologists,” thoughtful scholars of the early 1800s who took the record of the rocks and the record of Scripture seriously. Hitch was persuaded that earth history, written in pages of shale and sandstone, would make everybody better, more intelligent citizens. He wrote a delightful book for his Congregationalist flock,The Religion of Geology probably the finest rumination of how rocks and fossils can be integrated with piety.

Hitch won the reputation as an inspiring lecturer at Amherst. Emily Dickinson, among many others, was enraptured by the stories of prehistoric New England and how the past had shaped the woodlands and gardens of the present day.

When Hitch took over the Geological Survey, the Connecticut Valley was already famous for red Jurassic rocks. Quarries were dug for paving stones, excellent for walkways, and massive sandstone blocks, ideal for constructing “brownstone” homes, college dorms and courthouses. (Alas, as coal-fired furnaces became common, acid rain ate into the Triassic-Jurassic sandstones and many brownstone monuments began crumbling in the mid-20th Century.)

Hitch and his crew found petrified remains in these beds: some fern-like fronds, stems of horsetail reeds, bits of fish and a magnificent bug, the larva of some ferocious water insect. The red rocks had petrified weather, too: some surfaces had the delicate pattern of raindrops. Others showed deep cracks produced by prolonged drying.

But the most abundant remains were tracks, thousands of them. Some of the littlest footprints were made by flat-footed, lizard-oid critters with long, supple toes in fore and hind paws. Much more common, and often of giant size, were tracks made by somebody very different — mystery animals who grew as big as elephants and shared a common body plan that kept Hitchcock’s powers of deduction busy for his entire career. It was a great quest — he was on the trail of the creatures who ruled the Jurassic world on land.

Giant mystery tracks exposed along a county road in Massachusetts, with the local farmers using the one-horsepower field vehicle to visit the site.

Giant mystery tracks exposed along a county road in Massachusetts, with
the local farmers using the one-horsepower field vehicle to visit the site.

Hitch pondered the prints made by the mystery toes. Almost two centuries before Microsoft and Apple, Hitchcock began a digital revolution, inventing new methods of deciphering the details of paws. He and his son scoured libraries for anatomical details of the class Amphibia, the class Reptilia, and the hot-blooded classes, the Mammalia and Aves. Then they ran digital experiments, chasing all manner of animals across muddy fields — including barefoot boys with cheeks of tan — so they could draw the arrangement of toes.

All this research gave the Reverend Hitchcock more insight into the animal sole than anyone had obtained before. Step by step, Hitch filled a dossier of clues that would lead him to a final identification.

Bakker - Hitch Bird Dino pt1 6

Barefoot boy track as drawn in Hitchcock’s great monograph. Little dots are raindrop impressions. Hitch found drop marks on rock slabs with the mystery monster tracks. There was no evidence, pro or con, that the boy or the monsters carried slingshots, a la Bart Simpson.

First Clue: Bipeds. Nearly all the mystery tracks, even the biggest, were made by animals walking on their hind legs alone. That was unlike the locomotion of most lizards and mammals. And unlike the way dinosaurs were restored — with huge shoulders.

Second Clue: Toe-walkers, not flat-foots. Usually there was not a trace of the heel so it must have been held high off the ground. That eliminated dinosaurs because the dinos were flat-footed — so said the brightest and best of Europe’s bone-sleuths.

Bakker - Hitch Bird Dino pt1 7

Third Clue: Long Achilles tendons. This clue was the biggie. Over 99 percent of the tracks showed nothing of the ankle and nothing of the front paw, because the mystery beasts were strict toe-walkers. But in a precious few fossils, the tracks captured the mystery animal as it squatted down on all fours to drink or sniff the earth. Marvelous. The entire backside of the ankle was pressed into the mud — the Achilles tendon wasn’t wide and flat like a lizard’s. It was gracefully elongated and slender. The front paws were tiny, five-fingered and carried short, sharp claws. Maybe there was a mark left by a stumpy tail — the track wasn’t clear on this point.

Hitchcock’s mind raced. What prehistoric monsters had ankles and front feet built that way? Not mammoths or rhinos. Those giant hairy beasts always had front feet wider than the hind, and the ankle was always short. Well then, what about frog-oids? The hopping amphibians did have long, powerful hind limbs, strong calf muscles and small hands. The thought of multi-ton froggies stomping over the Jurassic meadows was … well, weird. And exciting.

If not frogg-oids, mebbe … bandicoot-oids? Australia was famous for “low-class” mammals, the marsupials, which on average were smaller in the brain than antelope, deer and other “normal” mammalians. Kangaroos and bandicoots had enlarged rear legs with super-strong calf tendons — plus little hands. Therefore, Hitchcock had to take seriously the idea of Massachusetts being overrun by Jurassic bandicoots bouncing about, as big as bull African elephants.

The Usual Suspects: Giant prehistoric beasts who might have made the tracks.

The Usual Suspects: Giant prehistoric beasts who might have made the
tracks.

And then there was the original suggestion made about 1800 by farmers who dug tracks on their land: Maybe it was Noah’s raven. The Flood Story in Genesis says Noah released a raven from the ark to test the depth of the water. The raven didn’t come back, so Noah concluded that some bare land had appeared. The Noah reference was a joke, an i.d. offered with a chuckle. But, indeed, to the un-trained eye, the Jurassic mystery tracks did have an avian gestalt …

… and Hitchcock could feel that he was getting close to the final answer. He needed just one more new type of CSI analysis, a quantitative sole-searching that would finger the culprit and reveal, once and for all, the identity of the Jurassic rulers.

Hitchcock’s Digital Data Base -- one page of the great monograph of 1858. Paleo-podiatry would enable the Reverend to solve the mystery of the Jurassic tracks.

Hitchcock’s Digital Data Base: one page of the great monograph of
1858. Paleo-podiatry would enable the Reverend to solve the mystery of the Jurassic tracks.

The guts stop here: Delve deeper into dinosaurian intestines with Dr. Bakker

Attention all Dino-Nerds! Put Your Anatomical Expertise to Work. Prestigious Careers Await in the Field of Gastroenterology.*”

Bakker Dino Guts 1

Where the guts fit in a T. rex. The pubic bone (yellow) sticks down and won’t let the intestines expand behind the hip socket.

Often, I get approached by parents who fret over their dino-fixated kid. “You gotta help us, Doc. All she wants to do is read about fossils. Will she ever find a respectable career in the real world?”

I can reassure Mom and Dad that studying dino anatomy can lead to well-paid and honorable occupations — for instance, as a professor of anatomy or a foot surgeon or a knee specialist. Or a gastroenterologist. Being a gut doctor is becoming especially attractive now because aging yuppies are suffering from decades of intestinal abuse from spicy nachos and a misplaced reliance on gluten-free pizza.

So, adults, encourage the children to delve deeply into the dinosaurian intestines. It’s fun. It’s educational. It might pay off — big time.

T. rex was a gut-less wonder

The first step toward a visceral understanding of dinos is to face the fact that T. rex was a gut-less wonder. Consider the rexian body cavity. The space available for guts is severely limited. That’s because the intestines must stop at the pubic bone, the big prong that points straight down from the hip socket. It’s inviolable anatomical law: No intestines can be behind the pubis!

In a rex, that means all the guts are in front of the hip socket and there just isn’t a lot of room here. You might argue that rexes were forced to be pure carnivores because they needed high protein food that could be digested with a minimum weight of gastric equipment.

(Vegan advice: A gentle admonition to all my vegan friends in Boulder, Colorado: High fiber plant food demands big, complicated gut compartments, a series of vats where the fodder is soaked and softened, worked upon by microbes that secrete the enzymes needed to break down fiber. That explains why Herefords and zebras, which are consummate digesters of grass, have naturally rotund tummies. Contrary to widespread myths, we humans, when we first evolved, were not adapted to high fiber, animal-free diets. When Australopithecus evolved into our genus Homo, the size of the gut shrank dramatically. So we had to specialize in protein-rich food, such as eggs, baby birds, grubs, turtles, bunnies and antelope carcasses scavenged from unwary saber-tooth tigers — plus, of course, nutritious fruits and nuts and tasty tubers excavated with digging sticks and roasted over the fire. Fire was domesticated at about the time our guts diminished in volume. Cooking releases food value otherwise unobtainable with our small-size intestines. Today, a modern human can indeed survive on a plant-based diet but you choose your veggies carefully. And cook ‘em.)

Bakker Dino Guts 2

Fowl guts.

Chickens that don’t fall over

Now that we’ve learned the basic laws of gut size, we are ready to unlock the mystery of the balanced chicken. You’ll remember from the previous post that barnyard fowl have exquisite balance on just two legs, despite the lack of a heavy tail.

Here’s another fowl mystery: Chickens have formidable digestion. They can extract food value out of raw grains and plant fiber far better than we humans can. The secrets to balance and digestion are one in the same — the gut-wrenching development of the pubic bone. When an embryonic bird in its egg is just beginning to develop a pelvic skeleton, the pubis points down, sorta like an adult T. rex pubis does. But when the chick hatches, the pubis has rotated completely around so it points backward and the guts expand behind the thigh.

Brilliant! The pubic re-alignment has doubled the potential room for intestines. And all that new weight of intestines is behind the hips, and therefore, confers perfect balance without any sort of ponderous tail.

Pubic-wrenching is a splendid osteological trick. Some dinosaurs did exactly the same thing. Stroll past our fine duckbill skeletons. Fix your gaze on the pubic bone. It’s rotated backward, just like a four-ton version of the barnyard fowl.

The duckbills go even further in gut expansion than do most birds. The pubis and ischium (the other lower hip bones) are so extended toward the rear that the guts gain another yard or two of length and allow another couple of chambers for microbial action on the food. All those extra digestive vats would let the duckbill G.I. tract break down even the toughest, most fibrous vegetables.

Duckbills win the award for longest gut tract of any dinosaur. And, probably, had the least constipation problems.

There’s a word every dino-nerd learns in the first grade: “ornithischians”. The simple meaning is “dinos with bird-style hips,” and that denotes the many species, like duckbills, that have undergone gut-wrenching. Stegosaurs wrenched their pubes, as did Triceratops.

Make a game of it! Go through our Fossil Hall with the children seeing how many different skeletons show the backwardly-bent pubes. Make the whole family pubo-literate!

Bakker Dino Guts 3

Before and after gut-wrenching experience: Top duckbill dinosaur shows how intestines would be limited if the animal had the primitive, vertical pubis. Bottom duckbill shows the real bent-back pubis and ischium.

When I skulk around our tour guides as they talk to school groups, my rib cage swells with pride. Our docents are the best! So I want to add an advanced bit of pubic-lore here. Stegosaurs and many other gut-wrenched herbivores do something tricky, pubis-wise.

After they evolved the backward-pointing pubis, these dinosaurs grew new pubic prongs — one on each side of the rib cage — that pointed forward and outward. This new set of prongs didn’t change the gut layout at all. The new prong lies outside the body cavity. The guts lay between the left and right new prongs.

What good did the new prong do? A stout muscle probably attached to it and ran back to the thigh to help swing the hind leg forward. If your child is considering med school, tell her that this muscle is what we call in humans the “psoas.

Bakker Dino Guts 4

Colorado State dino, Stegosaurus, showing the new prong of the pubis that points forward. Don’t confuse it with the true pubis!

And now, the ultimate Darwinian inquiry into gut-wrenching, the question that earns me sour stares from all my creationist relatives (37 full cousins on one side, 97% creationists)…

Here’s the query: When did pubic-twisting happen in the evolution of birds?

The chicken diagram I used earlier works pretty good for all modern day birds — every single one of the 10,000 species. From hummingbirds to ostriches, today’s avian species have the strongly wrenched pubic shaft and the attendant elongation of all things intestinal. No modern bird has the vertical pubis and short gut of a T. rex.

Bakker Dino Guts 5

Diagram of Archaeopteryx from Heilmann’s 1926 book “Origin of Birds”, modified by me in 1958. Heilmann explained the mix of bird and pre-bird features.

Archaeopteryx surprises

When first discovered in the 1860s, the Late Jurassic Archaeopteryx was an evolutionary celebrity, a missing link combining perfectly formed avian designs with archaic dinosaurian features. The first “Archie” skeleton excavated was jumbled but it certainly looked like the long, thin pubic bone was bent back in standard bird configuration. “Archie” also possessed another definitive bird device — the lagoonal, limestone-preserved imprints of fully-formed flight feathers.

Some dino characteristics were retained too: sharp little teeth, curved claws on the fingers, separate bones in the wrist (modern birds fuse up the individual bony units), and a long bony tail. The Archie was dubbed “Ur-Vogel” in German, an event which solidified the critter’s place in nature.

“Proof that creationism is wrong and Darwin is right!” shouted many an agnostic in 1868. In fact, the chap who coined the term “agnostic,” Thomas Henry Huxley, led the charge in proclaiming birds as descendants of wee dinos. Huxley’s favorite dinosaurian was Compsognathus, the original “Chicken-Dino,” a Late Jurassic carnivore extracted from the very same lagoonal rock that produced Archaeopteryx.

The Compy skeleton was cute as a button — so small that Huxley could imagine it perched on his shoulder during debates about Darwinism. When I began reading dinosaur books in the 1950s, the Compy was still the tweensiest dino known and several kids’ stories had a pet Compy following a second grader to school.

That image was just too cutesy-pootsy, too Disney, and the Compsognathus needed a makeover to give the species gravitas. The Jurassic Park franchise of the 1980s did just that. In the first Jurassic Park book, Compys are turd-eating pack-hunters that would jump up into a crib in a children’s hospital to bite off the kid’s nose and cheeks and rest of the face. That scene definitely stripped away the excess cutesy.

In the movie Jurassic Park, the Compys were upgraded to frilled little monsters that spat narcotizing pea-soup in the face of characters before biting off their noses, cheeks and rest of their faces. That scene ripped away the excess pootsy.

Movie villains can seem especially evil when they begin as pint-sized plush toys and then metamorphose into killers. Remember Gremlins and Chucky? (Maybe the writers of Jurassic Park scripts were trying to do to Compys what Miley Cyrus did for herself — take an adorable little star and remake the image so it seems more adult and more formidable. I believe that, when you go slow-motion through the Jurassic Park movie, you can see some of the Compys twerking.)

(Be advised: Jurassic Park books and film mix and match parts from three different dinos: (1) The true Compsognathus, beloved of agnostics; (2) The enigmatic pro-compsognathids known only from incomplete Triassic specimens; and (3) The distant compy cousin, the hefty 20-footer, Dilophosaurus, from the Early Jurassic. None were poisonous. None could spit. But recent discoveries from China reveal a raptor with teeth grooved like a gila monster’s — that means poison glands dripped venom down the grooves into wounds. Cool.)

Bakker Dino Guts 6In all three real dinos that inspired the Jurassic Park Compys, the pubis pointed downward and forward, the primitive configuration for carnivorous dinos and retained in our Texas Coelophysis. No gut expansion here.

Bakker Dino Guts 7

Bambiraptor, a little raptor-type dinosaur from the Late Cretaceous. Diagram done for Dr. David Burnham and me when Bambiraptor was named. Note that the pubis is bent back just a bit.

In the 1970s, Yale’s John Ostrom rediscovered Huxley’s insights. He used the recently discovered Deinonychus and its kin to prove that raptor-type dinos had hands, feet and a tail nearly identical to what Archaeopteryx possessed. But raptors still had primitive pubic bones that were bent back just a little bit. See the raptor-pubes for yourself in our “Julie-raptor” skeleton on display at HMNS or in the Bambiraptor skeleton in the lab (come by and take a look).

So, because of its superior pubic wrenching, Archaeopteryx was entitled to be hailed as more advanced than most raptors.

That made us all happy because we could make a nifty evolutionary scenario — an early raptor-like dino, a Jurassic version of Deinonychus, evolved into an Archaeopteryx-oid and then the Archie-oid evolved into a modern bird in the Early Cretaceous. Take that, my creationist-cousins!

(By the way, don’t let TV’s South Park mislead you; the plural of “pubis” is “pubes,” and it’s pronounced “pew-bays” and not “pewbs.”)

But then came the inevitable Oops Moment. That happens whenever we get too cocky.

Our friends at the Thermopolis Dinosaur Center in central Wyoming announced they had obtained a near perfect Archaeopteryx in 2006. I rushed up to ogle it, armed with a zillion photos of all the other Archie specimens. I stared at the pubes.

The new specimen and the other best specimens showed that the simple pelvic scenario was wrong. The real, undistorted Archaeopteryx pubis pointed straight down. No backward wrenching at all. In other words, Archies had no gut expansion whatever. The Ur-Vogel was no more advanced in this one key hip feature than an allosaur or a tyrannosaur.

Bakker Dino Guts 8

A very accurate diagram of Archaeopteryx, drawn by the magisterial paleontologist Peter Wellnhofer, who is the all-time expert on Jurassic pterosaurs and birds. Note the disturbingly vertical pubis.

Dang, dang, double dang

In this one famous feature, the backward wrenching of the pubis, Archaeopteryx turns out to be less like a modern bird than Bambiraptor or Deinonychus. Gosh … nearly every ornithischian dinosaur has more advanced pubic positions than does an Archaeopteryx.

We should’ve known. Evolution hardly ever goes in a neat, straight line. The origin of birds didn’t come about as one undivided line of dinos that gets better and better, more and more like a chicken, from the Triassic through the Jurassic and then into the Cretaceous. Darwinian family trees are much more complicated and much more confusing — more like tangled blackberry bushes, full of short branches going off in all directions. There are side branches and side branches coming off the side branches.

Archaeopteryx itself couldn’t survive by being a mere ancestor; it had to fit into its local environment; it had to be adapted to its immediate surroundings. The short gut and un-wrenched pelvis worked fine. A cluster of raptor-like dinos, with minor variations in pubic slant, shared the basic Archaeopteryx blueprint — and they too thrived for millions of generations. Even in the latest part of the Cretaceous, un-wrenched guts with vertical pubes contributed to the success of little Bambiraptor type predators.

Finally, after the Cretaceous ended, all the raptor-type dinos and all the birds with vertical pubes were extinct. Now, in today’s habitats all over the world, no bird or bird-like animal operates with the un-wrenched gut. Why? Did the short gut prove inadequate somehow in the long run? Could be. But we must remember that short-gutted birds and raptor-like dinos had done very well since the Mid Jurassic to Late Cretaceous, and that’s a full 100 million years. It’s not totally true, the old adage, “No guts, no glory.”

* It’s traditional for paleontologists to teach anatomy to pre-meds. I did that for years: at Harvard, then at Johns Hopkins. Thomas Henry Huxley, who worked out relations between little dinos and birds in the 1860s, also taught courses in basic dissection. It’s even more socially acceptable to be a genuine medical doctor who also digs fossils.

True story, not a Seinfeld episode: When I visit my mom at the retirement home, she introduces me as “my son, Dr. Bakker.” All the octogenarian ladies lean forward smiling. Then, politely, they begin to ask specific questions about certain medical conditions. Mom whispers, “He’s not a real doctor…” and all the ladies lean back with a slight curl of disapproval in their smiles.

Nota bene: The new book Ten Thousand Birds, (Princeton University Press), is wicked good — best ever done on our feathered species. Beautifully written. Everyone should get a copy.

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.

Digging in the dirt: Getting to know the Dimetrodon of the Texas Permian Red Beds

I love my job. Not everyone can say that. My avocation and vocation are as two eyes with one sight (paraphrasing Robert Frost). Part of that job was taking a group of 15 patrons up to the Museum’s dig site outside Seymour, Texas. There, under the tutelage of Dr. Robert Bakker and David Temple, the group learned how to properly excavate bones of ancient animals —  in this case, Permian synapsids, amphibians, and fish.   

I got to go through a spoil pile (the pile of debris and castoff that others have thrown aside), and found several bits of our very early ancestors, the synapsid Dimetrodon.  I also worked on removing the overburden (the rock and dirt that is over a site we want to excavate), and found bits from a dorsal spine of a Xenacanthus, an ancient shark. It was the fulfillment of a childhood dream (as I child I played paleontologist rather than fireman and my first Deinonychus is still buried out back at my childhood home).

But I’m not the only one who dreamed of finding fossils in Texas.

Noted Swiss naturalist Jacob Boll came to Texas in 1869 to join La Reunion commune that is located in the current Reunion District of Dallas. (The Reunion Tower is named in honor of that small settlement.) La Reunion commune was responsible for the first brewery and butcher shop in the Dallas area. It also helped Dallas become the center for carriage and harness making.

Jacob Boll came over to set up high schools based in scientific inquiry. Through the late 1870s, he searched for fossils for Edward Drinker Cope, the noted “Bone Wars” paleontologist. Boll found over 30 new vertebrate species from the Permian period, which can be seen in the collections of the American Museum of Natural History.  Unfortunately, on his last trip, he was bitten by a rattlesnake, wrote some final letters to his family, composed a short poem in German, and died.  

In the Permian period, Texas was very different from today. Near Seymour, there were rivers and seasonal flood plains. However, even with this picture, there are still unexplained factors about the life of Dimetrodon — one being that there was not enough prey to sustain the population that we have found in the fossil record. While the Dimetrodon were making sushi out of Xenacanthus and chewing on some Trimerorhachis legs (like frog legs, only much shorter), there was not enough food to go around.

Now add to this case the curious fact that almost no Dimetrodon skeleton found has an intact tail. Anyone who has been to a good Cajun restaurant will know that the best meat on an alligator is the tail. And Dimetrodon would agree — hence the lack of tails.

But even this does not account for all the food necessary to keep all the predators alive.  Where is the missing food?

Dr. Bakker gave us a couple of hints as to what he thinks is the answer. 

 A few miles away from the site, there is an old Permian river basin where we find Edaphosaurus, a large Dimetrodon-like herbivore. Was it possible for Dimetrodon to walk a few miles, ambush an animal about its size, then walk back for a rest? This would provide food for the population.          

If you are interested in learning more about the Texas Red Beds, join us for our Fossil Recovery Class on May 20. You can go through some of our collection from the trip and learn about fossil collecting and identification techniques.

Click here for more information.