high, continuous output of energy. Since pterodactyls definitely
were powered fliers, it's reasonable to suppose that Baron Cu-
vier's Pterodactylus warmed its own flesh with the heat of its own
exertions as it flapped through the Jurassic skies.
There's one serious stricture against Seeley's view that ptero-
dactyls were self-heating. Small animals—such as Pterodactylus and
most of its Jurassic kin—lose heat rapidly through their skin.
Hawkmoths succeed as self-heating fliers because their flight-mus-
cle compartments are insulated by the outer covering of hairlike
scales. The small pterodactyls would have required a coat of hair,
or some good substitute. However, most paleontologists have as-
sumed, since pterodactyls were classified as "reptiles," that they
had a naked, scaly skin. Such images certainly dominated the res-
torations of pterodactyls until 1970, when a startling report ar-
rived from a Russian paleontologist: Hairy pterodactyls had been
found in Russia. Professor Sharov had been engaged in separating
the slabs of Jurassic lake beds which preserved delicate leaves and
insects. In one split slab lay a pterodactyl—not unusual in itself.
But highly unusual was the near-perfect preservation of the pter-
odactyl's body covering—a dense coat of long, hairlike scales.
292 I DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
Sharov's pterodactyl had been as warmly clothed as any hawk-
moth.
Other specimens have confirmed Sharov's discovery. Flying
dragons as a group seem to have been insulated. Were they alive
today, it is very much to be doubted whether biologists would place
them in Class Reptilia. The dragons of the air lived their lives with
adaptations beyond the traditional limits of the term "reptile."
How, then, were the pterodactyls related to dinosaurs? Pter-
odactyls show some clear signs of sharing a common heritage with
crocodiles, dinosaurs, and birds; for example, their snouts in-
cluded a large hole in the bones of the face, a hole filled in life by
the anterior jaw muscles. Most authorities on the history of ver-
tebrate evolution place pterodactyls as uncles of the dinosaurs—
not ancestors of dinosaurs, but relatives of their ancestors. I sus-
pect, however, that the true relationship between pterodactyls and
dinosaurs was far more intimate. A few years ago, Jose Bonaparte,
a very sagacious Argentine paleontologist, published a keynote
paper about a small beast from the Triassic beds of Argentina. This
graceful creature was named Lagosuchus ("rabbit-crocodile") on ac-
count of its long, rabbitlike legs. (The Greek root suchus shouldn't
be taken too literally as crocodile; in scientific jargon suchus is used
for any sort of reptilelike creature and has even been applied to
some froglike amphibians.) Bonaparte pointed to one feature of
the rabbitcroc especially reminiscent of all flying dragons: the La-
gosuchus 's neck was long and had joints arranged to produce a nat-
ural S-shaped curve. True crocodilians never have such a sigmoid
flexure in their necks, and this adaptation, considered with Lago-
suchus's light overall build, makes it a good candidate for proto-
pterodactyl. It's possible to imagine rabbitcrocs bouncing over the
landscape, scurrying up trees, leaping from branch to branch, and—
just maybe—evolving a wing membrane.
Rabbitcrocs offer other evidence of their potential ancestral
status, not just for pterodactyls but for dinosaurs too. Early dino-
saurs of all sorts had the S-shaped neck posture. Lagosuchus also
had a head shaped like that found in both early dinosaurs and early
pterodactyls, particularly in the way the supporting strut for the
lower joint of the jaw is arranged.
Jose Bonaparte was kind enough to send me a copy of his pa-
per before it was published. I was surprised at how similar our ideas
DINOSAURS TAKE TO THE AIR | 293
Lagosuchus nips at a
furry protomammal.
about the pedigree of dinosaurs were—surprised because both of
us had independently concluded that the orthodox view of the di-
nosaur ancestry was incorrect. According to orthodoxy, the two
great dinosaur clans, the beaked dinosaurs and the meat-eaters, had
evolved from quite different ancestors (brontosaurs supposedly
evolved from early meat-eaters). By 1920 this view had gained wide
acceptance, although the issues were never debated thoroughly. Jose
Bonaparte proposed that the truth was in fact closer to the older
nineteenth-century idea that all dinosaurs were one natural group
derived from the same ancestor. And, according to Bonaparte, La-
gosuchus was that ancestor. I had already come to the same conclu-
sion. In the dinosaurs' family tree, Lagosuchus was the ultimate
evolutionary grandparent, and, therefore, deserved the label of "first
dinosaur."
Could it be, then, that Lagosuchus was the ancestor of both
dinosaurs and pterodactyls? Taxonomically speaking, an exhilarat-
ing thought, because it would mean that the warm-blooded pter-
odactyls evolved from a very primitive ancestor of the dinosaurs!
If warm-blooded pterodactyls had evolved from early dinosaurs,
perhaps the early dinosaurs themselves had already become warm-
blooded. The case for the evolution of pterodactyls from Lagosu-
chus or from some very similar early dinosaur is fairly good. The
shoulders and ankles of pterodactyls display the same unusual
evolutionary modifications found in rabbitcrocs. Very primitive
reptiles of all kinds had collarbones (clavicles) that braced the
shoulder blades (humans retain this primitive bony strut, as do most
lizards). All dinosaurs, including Lagosuchus, either lost the collar-
bone entirely through evolution or had a drastically reduced one.
And pterodactyls likewise were without this collarbone. In all
primitive reptiles and true crocodiles a long bony strip, the inter-
collarbone (interclavicle), lies on the chest between the shoulders.
Lizards generally retain this inter-collarbone, but all dinosaurs lost
it or reduced it to very narrow splint. And pterodactyls too lack
the inter-collarbone.
Head, neck, and shoulder therefore all suggest that pterodac-
tyls evolved from a primitive dinosaur, and so does the ankle joint.
All dinosaurs had a hingelike ankle that allowed the foot to flex
foreward and backward relative to the shank. But the dinosaur-
bird type of ankle didn't allow the foot to twist much, so dino-
DINOSAURS TAKE TO THE AIR
295
Two kinds of ankle joints
saurs couldn't turn the soles of their feet inward as can monkeys,
most infant humans, and very agile human adults. Pterodactyls had
an identical basic plan in the structure of their ankles. Crocodil-
ians and their kin have a bent ankle-hinge line and so did most
Triassic uncles of the dinosaurs (the thecodonts).
Reconstructing the ancestry of a clan like the pterodactyls re-
mains an especially difficult challenge. Flying dragons s
eem to burst
into the world like Athena from the mind of Zeus, fully formed.
Even the earliest skeletons of pterodactyls already display fully
developed wings and the specialized torso and hips so character-
296 | DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
istic of the entire order. Cases like this in paleontology—and there
are many more—persuade many scholars that evolution doesn't
work slowly and continuously at one even pace. Instead, there ap-
pear to be times when evolution speeds up and suddenly produces
totally new adaptive configurations. Pterodactyls must have emerged
in one of these creative spurts of the evolutionary process. As of
today, no fossils have been discovered to show how the pterodac-
tyl's forelimbs became transformed into wings. But the S-shaped
neck, the simplified shoulder structure, and the bird-type ankle are
excellent clues to the ultimate ancestry of the dragons—the quick
and agile early dinosaurs of the Triassic Period.
DINOSAURS TAKE TO THE AIR | 297
14
ARCHAEOPTERYX PATERNITY
SUIT: THE DINOSAUR-BIRD
CONNECTION
In 1892, Congressman Herbert directed an energetic diatribe
against the fledgling United States Geological Survey, a new
agency given the task of mapping the landscape and exploring the
rock formations all over the continent. One-armed Colonel John
Wesley Powell (left arm lost to a Confederate minie ball at Shiloh)
was the vigorous driving force in the Survey office. Powell moved
so fast and far in Washington circles that his success bred all man-
ner of envy. His enemies sought any excuse for attack. The Sur-
vey office had just published a monograph describing its discovery
of birds with teeth. Herbert railed against wasting tax money on
godless nonsense about "birds with teeth." These birds, so infuri-
ating to the congressman and all the Survey's enemies, were the
fossil seabirds from the Kansas chalk deposits, birds from the Late
Cretaceous age, discovered and described in loving detail by Oth-
niel Charles Marsh, professor at Yale. Marsh was supported in part
by government money and his monograph was issued as part of an
official government series. But Congressman Herbert's accusa-
tions of fraud and boondoggle were totally wrong. Marsh had in
fact personally paid most of the costs of research and all the extra
expenses of running gilt-edged copies of the monograph, special
gift editions he sent to scientists all over the world. An attack against
"birds with teeth" was, in any event, guaranteed to bring chuckles
from the assembled House of Representatives; pure science was a
298 | DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
Arcbaeopteryx
Marsh's Cretaceous toothed
bird, Hesperornis
safe target for election-year calumny. Surveys of flooding and coal-
mining areas were proper red-blooded topics for the Geological
Survey, but of what earthly use was a thick book about long-dead
seagulls that supposedly had teeth?
Across the Atlantic, in the great university towns and mu-
seums, Marsh's monograph enjoyed a totally different response.
"One of the strongest proofs of my theory," wrote Charles Dar-
win about the fossil Kansas birds. Thomas Henry Huxley could
barely contain his delight: Marsh's birds were a devastatingly ef-
fective weapon for beating down the prejudices and half-truths
published daily by the anti-evolutionists. Meticulous German an-
atomists nodded their agreement about the conceptual blow struck
by Marsh's Odontornithes ("toothed birds"—both the title of the
monograph and Marsh's name for his new order of ancient tooth-
bearing birds). Even European anti-evolutionary scholars (and only
a few good ones were left in 1885) regarded Marsh's toothed birds
as the long-sought anatomical intermediate between advanced
reptiles and modern birds.
Marsh's Odontornithes deserved every bit of the scientific at-
tention they stirred up. The battered skeletons of fish-eating birds
from the ancient tropical seas of Kansas became key arguments
for the capabilities of the evolutionary process. Darwin had in-
sisted evolution could alter organic forms to such a degree that it
could bridge the great gulf between the Class Reptilia and the Class
Aves. Anti-Darwinian critics retorted that Natural Processes might
be able to change one species into another closely related form—
create a wolf from a coyote, for example. But God's law suppos-
edly forbade a lizard or a crocodile from transmutating into an
ostrich or a whippoorwill. Even in our own day, the Creation Science
group in California grinds out pamphlets bearing the same mes-
sage: One warbler "species" might transform into another, but all
birds have always been true birds and the first sprang full-blown
from the creative hand of God.
Since all birds in the modern world are toothless, the tooth-
less condition was regarded as an immutable part of the definition
of Class Aves. Marsh's fossils had undeniably been birds—the
smaller ones, Ichtbyornis ("fish-bird"), possessed powerful wings
constructed nearly exactly according to the plan found in living avian
species. Marsh's bigger bird, Hesperornis ("western bird"), had clearly
been flightless—only the remnants of wing bones remained—but
ARCHAEOPTERYX PATERNITY SUIT: THE DINOSAUR-BIRD CONNECTION | 301
its vertebral column and hind legs were of typically avian architec-
ture. Hesperornis had clearly swum like a loon, with powerful strokes
of its hind feet, in a thoroughly avian manner. So far so good as
far as the creationists were concerned. Marsh's Mesozoic birds had
had certifiable avian characteristics. But both Ichthyornis and Hes-
perornis had had teeth set in their jaws—sharply pointed, curved
teeth with big roots, just like those of crocodiles. And Marsh de-
tected other more subtle remnants of reptilian ancestry: the upper
wing bone (humerus) of Ichthyornis featured a wide crest for sup-
porting the flight muscles, and this bony crest more resembled the
one along a dinosaur's arm bone than the structure found in any
modern birds. Ichthyornis also had simple dinosaur-style joints be-
tween its neck vertebrae—the vertebral bones met at flat bony
surfaces, unlike the strongly involuted, saddle-shaped joints of all
modern birds. Clearly, Marsh's Cretaceous birds bridged the gap
between bird and dinosaur.
These birds were part of the one-two-punch avian paleontol-
ogy delivered against creationism in the 1860s and 1870s. In 1861,
the lithographic limestones in Bavarian quarries yielded a fossil-
ized bird from the Jurassic Period, Archaeopteryx (ancient wing).
The Bavarian discovery consisted of a nearly complete skeleton of
a dinosaurlike animal, strongly resembling Ornitholestes, with long
hind legs and a very long tail. But there, on the carefully chipped-
out limestone slabs, impressed into the fine limy mud before it
had hard
ened, were also the unmistakable impressions of long flight
feathers attached to the forearm and wrist and big tail feathers
trailing behind.
Inveterate creationists, then or now, never allow their faith to
fall victim to facts. But to any careful, unbiased observer, it was
clear that the fossil bird from the Age of Reptiles consisted of a
genuine missing link between classes. The fossil bird of 1861 dis-
played one undoubtedly obvious reptilian feature: a bony tail that
was very long and not the abbreviated stub found on all modern
birds (any long tails of modern species consist of feathers only;
the tail bones are always stumpy like a chicken's). At first, the de-
tails of Archaeopteryx's skull and jaws remained obscure, because
the head was the worst preserved part of the skeleton. Certainly
no one expected the Jurassic bird to have teeth. Though Marsh's
birds from Kansas were much younger geologically than Archaeop-
302 I DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
teryx, he discovered the teeth in their jaws in 1872 and so re-
ceived credit for the first discovery of toothed birds. After that, of
course, evolutionists projected that Arcbaeopteryx too would prove
to have been equipped with teeth. Then, in 1877, the Bavarian
quarries yielded a second Arcbaeopteryx skeleton, and detailed
analysis uncovered the startling pro-Darwinian evidence: Ar-
cbaeopteryx too had had teeth, and everywhere the structure of its
joints and muscle processes had been much less birdlike and far
more primitive than those of the Odontornithes of the Creta-
ceous.
For paleontologists to accept an animal as a real "missing link"
between classes, the fossil is not only required to display an ana-
tomical structure intermediate between two distinct classes, but it
also has to appear in the "correct" sequence of time, intermediate
between the two classes. If the Darwinists were right, and birds
had evolved from a long-acting process, then the fossil record had
to read correctly, from bottom to top: The strata had to show (1)
the first primitive reptiles, then (2) advanced "reptiles" (dino-
saurs), then (3) primitive birds with teeth, then (4) more modern
birds with teeth, and finally (5) totally modern, toothless birds. Now,
Robert T Bakker Page 30
