primitive reptiles had been found low in the strata, in rocks from
the Coal Age and the Permian Period. Dinosaurs with birdlike
bodies made their entrance in the next-higher strata of the Trias-
sic Period. Arcbaeopteryx, a very primitive bird with teeth, showed
up in the next strata, the Jurassic. Marsh's toothed birds had been
more advanced than Arcbaeopteryx and appeared in the next pe-
riod, the Cretaceous. And, finally, truly modern birds without teeth
made their debut at the very end of the Cretaceous and the begin-
ning of the next epoch, the Paleocene. So it all fell into place ex-
actly as evolutionists would have predicted.
The stratigraphic proof for a Darwinian origin of birds ap-
peared incontrovertible—the rocks preserved the stages of de-
velopment in the exactly proper sequence through time. Any
impartial observer might conclude that if God had really created
birds, he must have been going out of his way to fool humanity
into believing in evolution.
Dinosaurophiles had reason to celebrate Arcbaeopteryx and
Marsh's birds. Evolutionists and nonevolutionists agreed on one
ARCHAEOPTERYX PATERNITY SUIT: THE DINOSAUR-BIRD CONNECTION I 303
Birds evolved direct from pseudosuchians or direct from dinosaurs.
point: the group of "reptiles" closest to the birds had been the ex-
tinct Dinosauria of the Mesozoic. Sir Richard Owen discerned avian
patterns in the feet of Iguanodon. Edward Drinker Cope believed
that the ankle of a New Jersey duckbill dinosaur was so birdlike
that he named the beast Ornithotarsus—literally, "bird-ankle."
Thomas Henry Huxley summarized arguments in favor of a di-
nosaurian origin for birds in one of his most famous and lyrical
304 | DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
pieces of scientific prose, published in the quarterly review of the
Geological Society of London. Huxley knew birds—he had worked
out a detailed classification of avian families based on the bony
structure of the palate, a classification still highly regarded today.
And Huxley knew dinosaurs and their kin. He had personally ex-
amined and discussed dozens of specimens. Huxley scrutinized the
anatomy of dinosaurs from nostrils to tail, claws to hips, revealing
that advanced meat-eating dinosaurs approached the true birds in
nearly all the details of their anatomy.
Huxley's case was impressive in documentation, persuasive in
argument: (1) Only in dinosaurs did he find the distinctive bird
type of ankle joint, where movement had been concentrated into
a single hinge running between the two rows of ankle bones. (2)
Only in dinosaurs had he found the great expansion of the upper
hip bone (the ilium) so characteristic of all birds. (3) Only in some
dinosaurs had the hind foot been arranged in a birdlike fashion
where the inner toe turned backward and the three main toes
pointed forward to produce the unmistakable footprint of birds.
In fact, some dinosaur tracks were so birdlike that they had been
mistaken for bird tracks when discovered in 1830. (4) Only ad-
vanced dinosaurs displayed the compact bipedal body fundamen-
tal to avian anatomy—the very short torso, massively braced hips,
long and highly mobile neck, and long hind legs. (5) Only in di-
nosaurs and pterodactyls had Huxley noted holes in the vertebral
bones for the air sacs which connected to avian-style lungs, and
the pterodactyls had been far less birdlike than advanced dino-
saurs in most other regards. (6) Only in some dinosaurs had the
pubic bone been turned backward exactly as in birds.
Over in America, Marsh for his part accepted the concept of
a dinosaurian ancestry for birds. And he pointed to the very bird-
like pattern of the small Bavarian dinosaur Compsognatbus, a
chicken-sized predator preserved in the same lithographic lime-
stone that yielded Arcbaeopteryx. Huxley favored a beaked dino-
saur as the most likely ancestor for the birds because the beaked
clan had had a backwardly reoriented pubis. In general, then, there
existed a firm consensus among the best paleontologists—Old and
New World scholars alike agreed that dinosaurs had been a bird-
like clan and birds were direct descendants of those dinosaurs.
Since the birdlike nature of advanced dinosaurs won wide ac-
ARCHAEOPTERYX PATERNITY SUIT: THE DINOSAUR-BIRD CONNECTION I 305
ceptance, late nineteenth-century naturalists couldn't dismiss the
Dinosauria as merely cold-blooded dead ends. If the proto-bird had
been a dinosaur, it wasn't unreasonable to suppose that some di-
nosaurs had had a proto-birdlike physiology. The resulting spec-
ulations about the dinosaur's metabolism therefore continued to
appear occasionally in respected European publications right up until
the 1920s. But all this changed in the late twenties. The claims
dinosaurs had to the paternity of birds were largely forgotten. And
the interrelated case for the warm-bloodedness of dinosaurs was
concomitantly dismissed for alleged lack of evidence. How had such
a revolution come about? Strangely enough, dinosaurs seem to have
lost their claim to having been the ancestors of birds because of
the best, most thorough book written about avian ancestry, a book
that got nearly everything right except its final conclusion.
Gerhard Heilmann's The Origin of Birds was first issued in
1925. It won nearly instant acclaim as the finest work on the sub-
ject, far wider in scope than any of Marsh's papers on toothed birds
and far more detailed than Huxley's essays. Heilmann remains a
popular and widely accepted author among paleontologists of all
stripes even today. Trained both as an ornithologist and anato-
mist, Heilmann's eye for evolutionary architecture was further
sharpened by his draftsman's skill—he penned his own drawings
of bones and muscles, depicting some of the liveliest and most ac-
curate restorations of dinosaurs in the flesh. Heilmann performed
Huxley's task over again, and did it better, demonstrating how di-
nosaurs did indeed exhibit extraordinarily birdlike adaptations of
their torso, neck, hip, ankle, and forelimb. But Heilmann was also
deeply disturbed by the possibility that the evolutionary argument
had been carried too far. As far as he could make out, all the bird-
like dinosaurs had evolved too far in one direction; they had lost
or greatly reduced the long collarbone of their proto-dinosaurian
ancestors. Yet all flying birds possess just such a very large collar-
bone resting against either side of their shoulders, which fuse to-
gether at their lower end to form that avian hallmark—the
wishbone.
Birds simply cannot fly without wishbones. The flexible, Li-
shaped strut formed by the fused collarbones braces the entire
shoulder against the stresses of flapping. Even Archaeopteryx had
already evolved a modern grade of wishbone, with long left and
306
DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
right collarbones fused together b
eneath the chest. Heilmann was
convinced that the direct ancestor of birds must have had large
collarbones, so that evolution could transform these structures into
the avian pattern. It was inconceivable to him that the bird's ancestor
could have undergone evolutionary reduction of the entire collar-
bone set. Were that the case, Heilmann would have been forced
to believe in a monumental reversal of the evolutionary process.
Like most paleontologists, Heilmann was a confirmed skeptic when
it came to evolutionary reversals. Minor reversals were conceiv-
Collarbones: large in birds,
rudimentary in most dinosaurs
ARCHAEOPTERYX PATERNITY SUIT: THE DINOSAUR-BIRD CONNECTION | 307
able. But complete loss of the collarbones followed by a re-evo-
lution of a very large set of them seemed totally incredible.
The very dinosaurs Marsh and Huxley had identified as most
birdlike were precisely the ones possessing little or no collarbone.
The small, long-legged carnivores such as Compsognathus were
certainly birdlike in overall design and in the details of their joints,
but most skeletons revealed no trace of a collarbone. At most, there
might be a tiny splint of bone running alongside the shoulder blade.
And such a splint might at most represent only the remnant of a
highly reduced collarbone. What was Heilmann to do with this ap-
parent paradox? The most birdlike dinosaurs had been totally un-
birdlike in this one indispensable characteristic. Heilmann had a
most astute sense of the general lessons taught by fossil history.
He knew that many times in geological history two distantly re-
lated tribes had progressed along very similar evolutionary path-
ways, so that after twenty or thirty million years the final products
were quite similar. An incautious observer might even be fooled
into believing in a close relationship between the two lines. Tas-
manian wolves are the classic example of this. They look very much
like true wolves. But the Tasmanian was a pouch-bearing marsu-
pial that evolved its wolflike configuration from a 'possumlike
ancestor in Australia. This was an evolutionary line totally sepa-
rate from the evolution of true wolves in Europe and North
America. Tasmanian wolves and true wolves aren't closely related
at all—each of their similarities evolved independently.
Faced with what he regarded as an impasse, Heilmann made
a very reasonable suggestion: He argued that both birds and di-
nosaurs had evolved from a common ancestor. This ancestor al-
ready had some of the advanced characteristics of both dinosaurs
and birds, such as long hind legs, but hadn't undergone reduction
of the collarbone. From this source two great evolutionary col-
umns had advanced through time, marching along parallel adap-
tive tracks. One track led to the birds, the other to the dinosaurs.
Therefore dinosaurs weren't the ancestors of birds, but only dis-
tant cousins.
There existed a fossil clan from the Triassic rocks that seemed
to fulfill nearly perfectly the role Heilmann ascribed to the com-
mon ancestor of dinosaurs and birds—the predatory reptiles known
as "pseudosuchians" (literally, "false crocodiles"). The false croc-
308 | DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
The Argentine ornithosuchid Riojasuchus, a group
supposedly close to bird ancestry
Deinonychus was a two-hundred-pound Cretaceous predator with a wickedly
enlarged hind claw for disemboweling prey. The Deinonychus family ranged
from 140 to 67 million years ago and left superb fossil skeletons in Wyoming
and Mongolia. These powerful hunters had an almost incredibly birdlike
anatomical structure from nose to tail—in fact, based on bone anatomy, we
would be justified in classifying them as either birdlike dinosaurs or
dinosaurlike birds. So avian were these dinosaurs, it is quite probable that
they had already evolved feathers for insulating their bodies.
odiles' hind limbs were longer than their forelimbs, their general
build was rather light, fast, and lively—precisely the type of loco-
motion to be expected in the forerunner of both the dinosaurs and
the birds. False crocodiles also displayed sharp teeth set in sockets
just like the dental arrangement found in toothed birds and di-
nosaurs (an important point because many primitive reptiles had
teeth that were fused to the jaw bone). Most important of all, the
best-preserved pseudosuchian skeletons contained big collar-
bones. Therefore false crocs had had precisely the right mix of
primitive and advanced characteristics to serve as the ancestors of
birds. Heilmann indicated one false croc in particular as a suitable
ancestor for the birds, Ornithosuchus from the Triassic red sand-
stones of Elgin, Scotland. Ornithosuchus means "bird-croc," and its
name was coined in the 1880s by a British geologist who had been
impressed by the beast's narrow, birdlike snout.
Heilmann's hypothesis won the day. Almost overnight, text-
books converted to the theory of the false crocs as the evolution-
ary ancestors of the birds. Dinosaurs were demoted from patriarchs
to distant cousins. And since dinosaurs were no longer considered
in the evolutionary line of the birds, they lost any claim to a gen-
uinely avian physiology. Heilmann certainly deserved credit for a
theory carefully worked out with attention to the nuances of evo-
lution. But, unfortunately, most scholars missed the main point—
Heilmann had substituted one implausibility for another. To be
sure, it was implausible that a collarbone would atrophy and then
re-evolve. But it's equally implausible that Archaeopteryx and di-
nosaurs like Compsognathus would evolve separately yet end up in-
controvertibly similar in nearly all characteristics. Heilmann's theory
required parallel evolution in unusually large doses, far larger doses
than would be required even for the Tasmanian wolves.
Heilmann's theory reigned as fact down into the 1960s. In
1964, John Ostrom at Yale discovered the very advanced preda-
tory dinosaur Deinonychus, a long-armed Early Cretaceous carni-
vore with a cruel-looking killing claw on its hind foot. Ostrom spent
two years carefully analyzing Deinonychus's place among the meat-
eating dinosaurs. Unknowingly he was being led directly to the
final and correct solution of the mystery of the origin of birds.
Biomechanical analysis applied to Deinonychus's bodily configura-
tion yielded evidence for exceptionally high levels of locomotive
ARCHAEOPTERYX PATERNITY SUIT: THE DINOSAUR-BIRD CONNECTION | 311
activity: both running speed and maneuverability. Quite clearly,
Deinonychus had had a great deal of birdness built into its limbs,
a birdness that would have expressed itself in life by a daily meta-
bolic regime more fitting for a ground bird such as a cassowary
than for the orthodox view of any cold-blooded dinosaur.
After completing his monograph on Deinonychus, Ostrom
planned for his next project—a study of pterodactyls. His two
projects, the first on Deinonychus, the second on pterodactyls,
seemed totally separate endeavors, and neither appeared to have
anything at all to do with the origin of birds. Yet his investigation
of pterodactyls was destined to lead John Ostrom to the discovery
of a new fossil. And that would lead him directly to the dinosaur
that was the true ancestor of all birds.
His serendipitous master stroke befell Ostrom in a Dutch
museum where he found a set of bony fingers on a limestone slab
out of those famous Bavarian quarries. The slab supposedly con-
tained yet another fragmentary pterodactyl skeleton, not an im-
portant find because dozens of complete specimens were available
from the same localities. But those long bony fingers, tipped by
needle-sharp claws, had been misidentified. They were not ptero-
dactyl at all but the rarest of the rare, the most sought after of all
Bavarian fossils, an Archaeopteryx. After fully a century of quarry-
ing, only those two early skeletons of 1861 and 1867 were known.
John Ostrom's was the third.
Alternating images flashed before his mind's eye as he scru-
tinized the Dutch specimen. He recognized the bony hands with
their three long, clawed fingers as belonging to Archaeopteryx. But
he also recognized in that hand a miniature version of Deinony-
chus's. Archaeopteryx had been pigeon-sized, its hand four inches
long; Deinonychus had been as heavy as an average man and could
stretch its hand a full nine inches. Yet the small bird hand and the
dinosaur hand were virtually identical in shape. Each finger and
wrist bone had been molded to the same peculiar biomechanical
pattern, an adaptive plan totally unknown anywhere in the animal
kingdom outside the Dinosauria. There was an important message
on this Dutch slab, and Ostrom read it correctly. Archaeopteryx and
Deinonychus had been very closely related. And birds were indeed
the direct descendants of dinosaurs.
Back at Yale, Ostrom constructed an overwhelming argu-
312 I DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
ment to prove his case. Between Archaeopteryx and Deinonychus the
long bony fingers were not the only things identical. So was nearly
Robert T Bakker Page 31