position it occupies in modern opinion. Dimorphodon's sharp teeth
jutted directly upward from the lower jaw and directly downward
from the upper. Therefore its strong bite must have been deliv-
ered by a quick, simple snap of uppers and lowers together.
But Dimorphodon's prey-catching devices weren't limited to that
simple snap of the fangs. Dimorphodon % neck was also constructed
to deliver rapid lunges. All pterodactyl necks were long and grace-
ful, and all had joints between the vertebrae of the neck which
allowed their owners to hold their head and neck in an S-shaped
curve. Since they all possessed large skulls compared to their body
size, this S-shaped curve allowed them to fly with their heavy heads
held far back over their shoulders. And this posture permitted
better distribution of weight both for flight and for walking, ex-
actly as modern pelicans tuck their big heads over their shoulders
DINOSAURS TAKE TO THE AIR | 283
Rhampkorhynchus
to gain better balance. But the S-shaped neck also provided Di-
morphodon with the ability to lunge; it could rapidly flip its head
and neck forward to make a quick grab at prey.
Other early pterodactyls shared the Dimorphodon's basic de-
sign but with variations. One Italian species had three-cusped mo-
lar teeth interspersed with tall fangs—a very strange arrangement—
crowded together along its jaws. The entire row of teeth could slice
fish into strips in a matter of seconds. Swallowing big prey is a
challenging biomechanical problem for today's shorebirds, be-
cause most can't easily tear up fish carcasses with their beaks, and
speed is of the essence because there are always thieves around
trying to run off with the prey. Most birds solve this problem the
same way dinosaurs did—the joints of the skull and jaws expand
sideways to enlarge the gullet's capacity. Pterodactyls faced the
problem but couldn't expand the rear of their jaws because the
skull's bones were too tightly knit. However, at the halfway point
of their lower jaws there was a zone of weakness that might have
allowed the jaws to bow outward so a large fish could slip down
the throat.
Fish and squid are tricky prey for an aerial hunter. These quick-
moving, slippery creatures can detect a pelican or puffin's dive just
before it strikes the water, and the whole school of them may scatter
in all directions. The pterodactyl's hunting tactics evolved to max-
imize the quickness of its strike. In the lustrous, lithographic lime-
stone of Bavaria are preserved the Late Jurassic squadrons of flying
dragons arrayed with a wide variety of head and body shapes. Still
in evidence are the straight-toothed biters similar to Dimorphodon
in design. But other tribes exhibit features for a tactic newly evolved
among flying reptiles—spearing with the head. Most numerous of
the tern-sized Bavarian pterodactyls is spear-headed Rhampho-
rhynchus ("beaked-jaws"). The S-shaped neck of primitive ptero-
dactyls was accentuated in this animal so that the head could be
carried coiled tightly against the shoulders. Rbamphorhynchus had
jaws and teeth shaped exactly like the fishing spears used by some
Amazonian Indian tribes today. Long, sharply tapered teeth in both
its upper and lower jaws were bent forward, so all the points would
converge to form a thrusting fish trap. Even the tip of the snout
and chin tapered to deadly points to form the apex of the spear.
Amazonian Indians hurl their spears at the heads of the fish: the
DINOSAURS TAKE TO THE AIR | 285
intermeshing set of points snags the fish's body, and its struggles
to escape only serve to drive the barbs in more deeply. Just so
Rhamphorhynchus could dive toward a fish, suddenly uncoil its S-
shaped neck flexure, and hurl its spear-shaped head at its prey,
impaling a hapless fish in the intermeshing barbs. This aerial fish-
ing spear must be ranked as one of the most effective fish traps
ever to evolve.
Baron Cuvier's Pterodactylus hunted for its daily ration in the
same reef-fringed waters as Rhamphorhynchus. But it had a totally
different apparatus for snaring prey. Extremely long, gently taper-
ing jaws terminated in a cluster of short, straight teeth. Pterodac-
tylus % jaws looked just like the barbed tweezers used to manipulate
squirmy invertebrates in today's zoology labs. And quite possibly
Pterodactylus was an airborne worm tweezer. It may well have
probed the sand flats like a Jurassic sandpiper, poking its long snout
into the burrows of polychaete worms, shrimplike crustaceans, and
sand fleas.
There's excellent evidence that one rather rare Argentine
species, the bristle-toothed pterodactyl, pursued a flamingolike style
of life. Modern flamingos derive their pink coloration from the
pigments stored in the tiny shrimplike creatures they filter from
the shallow salty waters. The shrimp, in turn, get this pigment from
tiny algae that they filter through their leg bristles. Captive fla-
mingos fade to off-white when given prepared zoo food, much to
the disappointment of curators and public alike. Fortunately, the
natural pigment can be replaced by simple food coloring (the same
kind used to dye Easter eggs) added to the flamingo's diet, so most
zoos can keep their birds in the pink. Shrimplike crustaceans are
a very ancient group, as are the red algae that are the ultimate
suppliers of the pigment. Salty pools must have hosted red algae
blooms in Jurassic days exactly as they do today. Then, as now,
both algae and shrimp were an excellent source of food for any
larger animal equipped to sieve them out of the water through an
anatomical strainer. Was there, then, a pink strainer pterodactyl?
Probably. The Argentine pterodactyl in question possessed a fla-
mingo-shaped mouth with a dense row of thin, bristlelike teeth.
Without question this bristle-toothed pterodactyl pumped water
through its mouth with its tongue, straining out tiny food particles
in the process. And since blooms of red algae were common in
286 | DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
Rhamphorhynchus fishing technique
briny water, it's reasonable to suppose it would often filter both
algae and shrimp, and behold, a pink pterodactyl!
Flamingos appear especially awkward when they are hard at
work feeding because their filtering bristles are in the upper jaw
and their head must be upside down to perform its function in the
water. Bristle-toothed pterodactyls didn't have to perform head-
stands, because their filtering apparatus was located in the lower
jaw, so the head could be lowered right side up into the water.
Curiously enough, flamingos and bristle-toothed pterodactyls aren't
the only examples of algae-straining aerialists to evolve in the his-
tory of life. Forty-five million years ago a long-legged duck with
flamingolike bristles in its lower jaw waded through the salty lakes
of Wyoming, Colorado, and Utah. Fossil beds laid down in these
&n
bsp; briny lakes preserve the skulls, skeletons, footprints, and even some
mound-type nests and the eggshells of the bristle-beaked duck.
These three filter feeders are an extraordinary example of how
evolutionary processes can shape unrelated clans into one and the
same specialized ecological mode.
While on the subject of color, Dimorphodons snout deserves
DINOSAURS TAKE TO THE AIR
287
comment. Seeley reconstructed this animal with a dark snout. But
more likely Dimorphodon's face was positively gaudy. Its high-
snouted profile was more like a puffin's than that of any other bird,
and puffins employ their tall beaks to advertise their social status.
Juvenile puffins start out quite drab in the snout, but adults are
marked by faces run riot with white, red, and orange stripes and
splotches. Dimorphodon % deep snout cannot be explained by any
hypothesis involving its jaw muscles or teeth. It's quite likely that
Dimorphodon % snout evolved its unique high contours to advertise
its owner's rank in pterodactyl society. Since pterodactyls were
highly visual creatures, with large eyes and bulbous optic hemi-
spheres in their brain, it's very probable in fact that colorful de-
vices evolved many times among the various branches of the family
The flamingo pterosaur
—Pterodaustro from
Argentina
tree. Of course there is no direct evidence allowing reconstruction
of the color pattern for any particular species of pterodactyl, but
their color must have evolved to brighten Jurassic and Cretaceous
skies in many ways.
Everywhere in the world's ecosystems the transition from the
Jurassic to the Cretaceous was marked as a time of disaster, dis-
turbance, and extinction. Flying dragons did not escape this vast
ecological shake-up. The experts divide all pterodactyls into two
great tribes: the long-tails and the short-tails. After the Late Juras-
sic extinctions wiped out most of the previously dominant long-
tails, the short-tailed species moved in to fill the Cretaceous skies.
Rhampborhynchus, with its fishing-spear head, was a long-tail; Baron
Cuvier's Pterodactylus was a representative short-tail. By and large
the long-tailed species did have fairly long tails—and at least some
of them possessed kitelike tail rudders. Professor Othniel Marsh
of Yale bought a superb Rhampborhynchus from German fossil
dealers in the 1880s and subsequently announced to the envious
Europeans that his skeleton possessed a tail rudder, previously un-
known. Rhampborhynchus carried a vertical diamond-shaped fin at
the end of its very long tail. The fin consisted of tough skin rein-
forced by rods of connective tissue. The entire tail could be en-
ergetically swished by muscles at the base of the tail. The precise
aerodynamic effects of this intriguing equipment aren't yet under-
stood, but the kite-tailed pterodactyl must have exercised precise
control over its maneuvers, at least at slow speeds.
Short-tailed pterodactyls generally had more specialized skulls,
longer necks, and longer forearms than their long-tailed fore-
bears—implying a fundamental change (still not well understood)
in flight mechanics. This short-tailed Cretaceous dynasty certainly
won an undisputed place in the book of aerial records, for it in-
cluded the largest flying creatures ever to evolve. Marsh made
headlines in the 1880s when he announced short-tailed pterodac-
tyls from Kansas with wingspans of twenty feet or more. But the
mind-boggling pterodactyl was yet to come. In the 1970s, Profes-
sor Wann Langston led teams from the University of Texas into
the scorching badlands of Big Bend National Park where the Rio
Grande makes its huge loop on its way to the Gulf of Mexico.
When Langston discovered a Cretaceous pterodactyl at Big Bend,
its upper arm bone measured twice the size of the next-largest
DINOSAURS TAKE TO THE AIR | 289
known, and its jaws indicated a head eight feet long. Preliminary
reconstruction, based on the wing plans of smaller species, pro-
duced an estimated wingspan of up to twenty meters—sixty-three
feet, greater than the wingspan of the old twin-engine DC-3 air-
liners. Quetzalcoatlus was featured on the cover of Science, the most
widely read scholarly journal in the United States. Immediately after
their paper came out in Science, Wann Langston and his students
were attacked by aeronautical engineers who simply would not
believe that the Big Bend dragon had a wingspan of forty feet or
more. Such dimensions broke all the rules of flight engineering: a
creature that large would have broken its arm bones if it tried to
fly. Quite a flap erupted over whether the Big 3end pterodactyl
could even have powered its wings in the up-and-down strokes
necessary for active flight. Under this hail of disbelief, Langston
and his crew backed off somewhat. Since the complete wing bones
hadn't been discovered, it was possible to reconstruct the Big Bend
pterodactyl with wings much shorter than fifty feet.
I believe Langston and his Texans were right—the Big Bend
aerial leviathan was stupefyingly large. Mechanical engineers go
often astray when analyzing the strength of skeletons. The most
common difficulty with their method is that they calculate the
strength of an arm bone as though the bone by itself had to with-
stand all the stresses of flapping the wings. If the pterodactyl were
a man-made machine, the wing skeleton would indeed bear all the
stress. But naturally evolved arms are far superior to mechanical
ones. The bundles of muscles sheathing the arm bones of birds or
humans contract to reorient stresses when the body is exercising
vigorously. Such contractions are automatic, since the muscles are
sent a constant flow of orders from the posture-control centers of
the nervous system. Therefore a live Quetzalcoatlus was stronger
than an engineering analysis of its bones might indicate. More-
over, calculating the stresses in a sixty-foot pterodactyl's wing is
also subject to extreme variation—the Big Bend animal may well
have flapped its wing from the wrist and not from the shoulder,
for example. And in fact until the joints of the wing are clearly
understood, any attempt to calculate stresses remains dubious at
best. In general, I believe it dangerous to argue a priori that
Quetzalcoatlus couldn't have been as big as seems indicated. The
theories of bioengineering relating to flight in live mammals are
290 | DEFENSE, LOCOMOTION, AND THE CASE FOR WARM-BLOODED DINOSAURS
still too crude to yield anything more than imprecise boundary
conditions that set limits only on the most extreme possibilities.
Based on the proportions from the wings of other Cretaceous
pterodactyls, the best estimate of the wingspan for the Big Bend
dragon remains, in my opinion, the original fifty feet plus.
Cretaceous pterodactyls from North America are notable not
only for their size but for their flamboyant head crests as well.
Pte
ranodon ("wing without teeth"—a reference to the toothless
beak), Professor Marsh's big Kansas specimen, had a long, narrow,
bony prong sticking out rearward from the top of its skull. What
was the function of this extraordinary cranial ornament? Some have
suggested this prong was a sort of rudder; others that it was a bony
banner for display and intimidation. Closely related species that
are very similar in body outline have little or no crest, so this
problem is complicated. And no bird, living or extinct, possesses
anything even remotely similar to Pteranodon s headgear.
On the subject of pterodactyls, two questions are enjoying
considerable debate: their warm-bloodedness and their relation to
the dinosaurs. Professor Seeley summed up the nineteenth-cen-
tury view: If pterodactyls flapped actively during flight, the heat
generated by their muscles would have warmed their bodies to
temperatures higher than that of the air. Seeley was almost cer-
tainly correct (he usually was).
DINOSAURS TAKE TO THE AIR | 291
Recently developed measuring devices such as those sensitive
in the infrared and ultra-violet allow zoologists to measure heat
production and body temperature in all sorts of creatures engaged
in various exercise. The various heat detectors and oxygen ana-
lyzers placed on creatures of small size have yielded startling re-
sults. Nineteenth-century zoology reckoned "warm-bloodedness"
as the highest level of adaptation, reserved for the top rungs of
Scala Naturae. Birds and mammals were clearly warm-blooded,
snakes and insects clearly weren't. But this view was wrong, as the
delicate apparatus of the late twentieth century reveals. Hawk-
moths are powerful, nocturnal flying insects whose torsos are cov-
ered with dense, hairlike scales. Elegant experiments show that
hawkmoths heat themselves with their own flight muscles. Before
they begin their mighty flights, hawkmoths send shivers of con-
traction through their powerful flight muscles, generating waves
of body heat. After the moth has raised its temperature above that
of the air, it takes off—a warm-blooded, fur-covered flier. As long
as it keeps flying, the hawkmoth keeps its body temperature high
through the heat of its own movements. Powered flight requires a
Robert T Bakker Page 29