ther birdlike characteristics turned up in the dinosaurs' backbone.
Many species of dinosaur had hollow chambers in their vertebrae.
In life, these bony caverns were filled with air sacs connecting to
the lung, just as in many birds today. Later nineteenth-century
discoveries made the dinosaur-bird connection very intimate. Ar-
chaeopteryx, the oldest fossil bird, was discovered in 1861 and made
headlines because it looked so much like a small dinosaur with
20 | THE CONQUERING COLD-BLOODS: A CONUNDRUM
One of the first dinosaurs discovered—the thirty-foot predator Megalosaurus,
dug up in the 1820s in England. Here the great megalosaur is attacking a sea
crocodile, Te/eosaurus.
In the 1860s Thomas Henry Huxley argued that birds descended from
dinosaurs, and that view is now being revived—the six-feet-long predator
Deinonychus, shown here attacking an ostrich dinosaur, is a near-perfect
missing link between dinosaurs and modern birds.
feathers. The great Darwinian orator and advocate Thomas Henry
Huxley pounded the pulpit of evolutionary theory by pointing to
Archaeopteryx as the missing link between dinosaurs and modern
birds.
It's important to be clear about the reverse definition as well:
what dinosaurs are not. Dinosaurs are not lizards, and vice versa.
Lizards are scaly reptiles of an ancient bloodline. The oldest liz-
22 I THE CONQUERING COLD-BLOODS: A CONUNDRUM
ards antedate the earliest dinosaurs by a full thirty million years.
A few large lizards, such as the man-eating Komodo dragon, have
been called "relicts of the dinosaur age," but this phrase is histor-
ically incorrect. No lizard ever evolved the birdlike characteristics
peculiar to each and every dinosaur. A big lizard never resembled
a small dinosaur except for a few inconsequential details of the teeth.
Lizards never walk with the erect, long-striding gait that distin-
guishes the dinosaurlike ground birds today or the birdlike dino-
saurs of the Mesozoic.
Snakes are lizard nieces—descendants of a close relative of
lizards. Some lizards have lost their limbs and slither like snakes,
but true snakes have specialized eyes and jaws. Snakes, of course,
are not at all close to dinosaurs.
Crocodiles and their next of kin, alligators, are unquestiona-
bly dinosaur uncles, relatives of dinosaur ancestors. Baron Cuvier,
Sir Richard Owen, and other early dinosaurologists discerned many
important anatomical characteristics shared by dinosaurs and croc-
odiles. For example, dinosaur teeth are set in sockets—so are the
teeth of crocodiles—whereas lizard and snake teeth are fused to
the inside of the jawbone without sockets. Dinosaurs have a deep
socket in the hip bones for the thigh, and so do crocodiles, but
lizards do not. Crocodiles even show the beginnings of birdlike
development in hip and thigh. Crocodiles first enter the chronicle
of the rocks long after lizards but a few million years before di-
nosaurs.
Frogs and their short-legged relatives the salamanders are am-
phibians, not reptiles. Amphibians lay water-breathing eggs, and
usually the newly hatched young breathe via gills for a while be-
fore becoming air-breathers. Like the reptiles, the amphibians have
"cold blood." ("Cold blood" means that metabolism is so low that
body temperature falls to air-ground temperature unless the ani-
mal can heat up by basking in the sun.) Amphibians have only a
very distant kinship to dinosaurs.
Turtles are marvelous organic creations and very worthy ob-
jects for contemplation, but turtles aren't dinosaurs. Turtles have
a scaly skin and a leathery or porcelaneous egg, points of resem-
blance to both lizards and crocodiles. But the body architecture of
the turtle is so thoroughly unique that after nearly two centuries
of research, turtle relationships are murky at best.
Are dinosaurs true members of the reptile class? Good ques-
BRONTOSAURUS IN THE GREAT HALL AT YALE I 23
Bird, crocodile, and mammal adaptations combined—the three-ton
herbivorous dinosaur lguanodon, first found in the 1820s in England. The
spike of bone on the thumb must have been a dangerous weapon.
tion. Hard to answer—that's what this book is all about. The late
nineteenth-century naturalists defined Reptilia by blood, skin, and
sex. If an animal had "cold blood," skin covered with scales, and
laid eggs on land, then it was a true reptile. Despite the obvious
similarities of design between crocodiles and birds, therefore, the
scaly, naked hide of crocodiles and their "cold blood" have per-
suaded most naturalists to separate them from the birds. Birds have
their own class, the Aves. But crocodiles are left in the Reptilia
with their more distant relatives, lizards, snakes, and turtles.
Birds and mammals differ from each other in extraordinarily
numerous ways, in nearly all details of their joints, muscles, and
other organs. But birds and mammals do share two key adapta-
tions which color their entire evolutionary style: both have insu-
lation for the skin (feathers for birds, hair for mammals) and both
are "warm-blooded" (they have such a high metabolic rate that their
bodies are generally heated from the inside). Mammals have their
own zoological class. Although the "warm-bloodedness" of birds
and mammals is very similar in physiological detail, it is quite clear
that the "warm-blooded" condition evolved separately, once in birds,
once in mammals.
Now, nineteenth-century science was self-consciously preoc-
cupied with "progress." The Industrial Revolution had wrought
such rapid advancement in machines, small and great, that mid-
Victorian scientists could see no end to the upward perfection of
technology. And Darwinism, in its vulgar "survival of the fittest"
version, seemed to preach that there was a natural law guiding the
continuous perfection of life forms through all geological time.
Which was most perfect? Homo sapiens, of course—especially a male,
English, Protestant Homo sapiens. And so our class, the Mammalia,
had to be the highest zoological grouping. Birds were close be-
cause, like mammals, they had insulation and metabolic control of
their body temperature.
Progress also meant freeing oneself from the uncomfortable
whims of the environment—the sudden changes in heat and light.
The poor reptile could bask happily on a rock in the sun but slipped
back into a chilled torpor when clouds blotted out the warming
rays. Not so the bird or mammal whose body furnaces burned so
fast and so continually that blood and flesh remained warm. And
Victorian biochemistry had progressed far enough to discover that
BRONTOSAURUS IN THE GREAT HALL AT YALE | 25
most vital processes function best when the body temperature is
nearly constant. English homes—upper-class ones, at least—were
enjoying the dependable warmth of coal-fed furnaces, devices that
finally made the damp winter climate cozy and comfortable. Clearly
&n
bsp; the highest zoological classes were the ones that had evolved an
analogous metabolic adaptation.
The zoologists of the last century knew well that there was a
case for a crocodile—bird relationship and an even better case for
a dinosaur—bird kinship. But the scientists of the time nonetheless
slipped into the habit of calling dinosaurs "reptiles!'—cold-blooded,
scaly creatures that laid eggs.
Nineteenth-century naturalists used their warm blood/cold
blood dichotomy to classify all vertebrates into two grand divi-
Two ways dinosaurs
could be classified—as
cold-bloods because
dinosaurs share
adaptations with
crocodiles, or as warm-
bloods because
dinosaurs have many
birdlike features.
26 I THE CONQUERING COLD-BLOODS: A CONUNDRUM
sions, one above the other. At the bottom were the "lower ver-
tebrates," the classes without metabolic control of their body heat.
Here were lumped all the fishes, the Amphibia, and of course the
Reptilia. At the top were the "higher vertebrates," the two classes—
Aves and Mammalia. Dinosaurs were thrown into the Reptilia and
so into the "lower vertebrates" by early naturalists, but an equally
good case could have been made to classify dinosaurs as primitive
birds. No one, either in the nineteenth century or the twentieth,
has ever built a persuasive case proving that dinosaurs as a whole
were more like reptilian crocodiles than warm-blooded birds. No
one has done this because it can't be done.
Generally speaking badges are harmful in science. If a scien-
tist pins one labeled "Reptile" on some extinct species, anyone who
sees it will automatically think, "Reptile, hmmm . . . that means
cold-blooded, a lower vertebrate, sluggish when the weather is dark
and cool." There are never enough naturalists around, in any age;
so most scientific orthodoxy goes unchallenged. There are just not
enough skeptical minds to stare at each badge and ask the embar-
rassing question, "How do you know the label is right?"
Be kind to colleagues, ruthless with theories, is a good rule.
A scientific theory isn't merely idle speculation, it's a verbal pic-
ture of how things might work, how a system in nature might or-
ganize things—atoms and molecules, species and ecosystems. But
old paleontological theories too often aren't treated roughly enough.
Old theories—like the reptilian nature of dinosaurs—are accepted
like old friends of the family. You don't yell at old Aunt Cecilia.
So hundred-year-old dinosaur theories live on without being
questioned, and too often they are assumed to be totally correct.
Even when such theory is caught in an error, it's likely to be
excused.
Traditional dinosaur theory is full of short circuits. Like the
antiquated wiring in an overaged house, the details sputter and burn
out when specific parts are tested. I have enormous respect for
dinosaur paleontologists past and present. But on average, for the
last fifty years, the field hasn't tested dinosaur orthodoxy severely
enough.
I'd be disappointed if this book didn't make some people an-
gry. A lot of modern scientists—even some paleontologists—in-
sist on saying that fossils are misleading. "Dead bones don't
BRONTOSAURUS IN THE GREAT HALL AT YALE I 27
metabolize so how can physiology in dinosaurs be discussed?"
Ecologists who study the Serengeti Plain or the rain forests of
Burma are impressed by the complex ways animal species interact
with each other and with their habitats: "How can a few spare bones
capture all the organic subtlety of long-extinct systems?" Many
people dismiss the record of the rocks as an incomplete and nearly
unreadable document. Darwin himself did that; he didn't trust fos-
sils to indicate the entire truth. But these views are wrongheaded.
The Book of Job—oldest in the Bible—admonishes, "Speak to the
Earth and it will teach thee." If we look and listen carefully, the
record of the rocks can unlock the richly textured story of the di-
nosaurs and their ways.
The Stonesfield specter. From the very first discoveries of dinosaurs in the
1820s there was proof positive that our mammalian order had existed under
the shadow of the gigantic dinosaurian monsters. Earliest of the dinosaur
quarries was the road-gravel pit in the Stonesfield Slate, where giant jaws of
Megalosaurus could be found with teeth so large that a single tooth was
longer than the entire jaw of the mammals found in the same strata. Shown
here, natural size, is Phascolotherium standing next to the lower jaw of
Megalosaurus.
28 | THE CONQUERING COLD-BLOODS: A CONUNDRUM
2
WYOMING REVERIE:
MEDITATION ON THE
GEOLOGICAL TEXT
From my Field Book, 1981
July 3, 6:35 A.M.
Como Bluff, Wyoming. 7,020 feet above sea level. No human being
or human structure visible. Air clear, dry, cool. A pair of mule
deer browsing along Rock Creek. Put the coffee water on the
Coleman stove to heat up. No one else is awake in camp yet, but
the smell of bacon will entice them out of their tents.
sil bones—but I'm still excited by the first dinosaur of the sum-
mer. I sit here on the crest of a little sandstone hogback, remnant
of a stream that flowed a hundred million years ago, and look down
on my crew's work of the last four days. It's becoming a sizeable
hole, a proper dinosaur dig, twenty-five feet across, dug by pickax,
army-surplus trenching shovel, icepick, and fingernails.
I saw my first dinosaur in that splendid Mecca for Mesozoic
relics, the American Museum of Natural History in New York, at
the age of nine. But those skeletons seemed tamed by civilization,
mounted as they were on steel and plaster, posed for the benefit
of countless parades of schoolchildren and tourists. A dinosaur in
the rock is different. This one before me is huge, and its six-foot-
long thigh bone, which would dwarf any elephant's, lies half ex-
posed to the Wyoming sunrise. Its coal black form is clearly etched
WYOMING REVERIE: MEDITATION ON THE GEOLOGICAL TEXT I 29
The great dinosaur graveyards
of the American West
against the surrounding pale rock by thousands of careful chisel
marks. This bone is a holy relic for me, as beautiful in its roughly
hewn outline as Michelangelo's bound slaves struggling to free
themselves from the enveloping marble.
From where I sit on the quarry's rim I can see the dinosaur's
great trochanters, the attachment site of the immense hip muscles,
and the bone surface pitted and rough where tendons and liga-
ments were anchored to the femur. A hundred thousand millennia
ago, those tendons and muscles were full of dinosaur blood cours-
ing through capillary beds, bringing oxygen to the cells that pow-
ered the stride of this ten-ton giant. Muscles pulsed in cycles of
contraction and release, and the hind limb, fully twelve feet long
from hip to toenails, swung through its stroke covering six feet
with every pace.
Broken chips of bone lie under my boots, wretched frag-
ments from now unidentifiable bones which had eroded long be-
fore we found the site. Even though I know I can't identify the
bits of bone, I pick one up anyway because there is something
special about the feel of dinosaur bone very early in the morning.
Some of the broken bits are incredibly delicate bubbles of bone,
a frothy texture of holes and vesicles that housed the living sub-
stance of the animal's cells. These bits crumble into shards if I rub
them too hard, but in life the brittle bone crystals were embedded
in a fabric of tough connective tissue, collagen fibers whose great
tensile strength combined with the hardness of the bone crystals
to produce a living bony architecture capable of resisting enor-
mous loads of both compression and tension. Collagen has long
since rotted away, along with all the muscle fibers and blood ves-
sels. But the fossilized bone faithfully preserves the canals left by
every capillary that made its passage through it to serve the dino-
saur in life. Those living cells, now gone, left one other signature
on this carcass. A black powder rubs into my gloves as I finger the
bone chips. This powder is carbon dust mixed with granulated bone,
the dried and distilled residue of all the cell membranes, cell fluids,
and organelles whose work within the bone was ended when the
dinosaur died.
Reverie is normal in Wyoming at sunrise. I suppose a no-
nonsense laboratory scientist, clad in his white lab coat and steely-
eyed objectivity, might think I was wasting my time communing
WYOMING REVERIE: MEDITATION ON THE GEOLOGICAL TEXT I 31
Our camp at Como Bluff and how the rock layers would look if cut through
vertically
with the spirit of the fossil beast. But scientists need reverie. We
need long walks and quiet times at the quarry to let the whole
pattern of fossil history sink into our consciousness.
As I walk back to camp from the quarry, I climb through the
ledges of hard rock, benches of limestone, each an irregular mo-
saic of ovoid nodules, each extremely hard and long-lasting in this