head and the prey's limbs point away. Then the snake opens its
jaws and begins to engulf the monkey. Not hurriedly, not with
crude gulping and gnashing of teeth, but deliberately and pre-
cisely, the snake draws the monkey's head and shoulders into its
mouth. We humans are limited by our rigid and brittle jaw, whose
right and left sides are firmly joined at the chin so that the width
of our mouth is fixed. The right and left halves of the serpent's
jaw are joined only by an elastic ligament, so the "chin" can stretch
MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS | 71
as the monkey's head is swallowed. Within both right and left lower
jaw, the snake possesses a hinge that allows even more expansion.
Our human jaws move sideways only slightly where they meet the
skull at the jaw joint, just in front of the ears (try moving your
jaw from side to side with your finger resting on the jaw joint—
you will feel only about Va" of movement). But the right and left
halves of the snake's jaw are hung on the skull by a long, folding
strut, divided into two hinged sections like a carpenter's ruler. As
the snake engulfs the monkey's shoulders, these joints swing out-
ward on their flexible struts, enormously increasing the gullet's di-
ameter to accommodate the outsized prey.
So far we have witnessed only the passive aspect of the puff
adder's swallowing act—the hinges and elastic joints being pushed
out by the prey's body as it is drawn into the snake's mouth. But
the greater marvel is the way the snake powers its jaws to drag the
prey down its throat. We think of swallowing as a minor muscular
feat. We chew a few dozen times and gulp. Down goes a little
masticated food accompanied by minor contractions of our tongue
and esophageal apparatus. Our chewing muscles do most of the
work; swallowing is not a major event. But since snakes don't chew,
the entire body of the monkey is actively drawn into the snake's
throat by the backward pull of fanged jaw bars, two above and two
below. Unlike the soft roof of our mouth, the snake's palate pos-
sesses bars of bones, studded with backwardly curved teeth, on
each side. The snake's jaw muscles can manipulate each palate bar
backward by itself, the recurved teeth dragging the prey backward
into the throat. After the bar has pulled as far backward as it can
go, the jaw muscles lift it up and forward, while disengaging the
curved teeth from the prey, and move the bar forward to start an-
other stroke. The lower jaws can also be retracted independently,
one side at a time, to aid in dragging the monkey down its throat.
To get a mental picture of the process as it might work in our
heads, imagine that your jaw could expand at chin and jaw joint;
imagine that you had two short hands, each holding a fork, at-
tached to the roof of your mouth. You have a big monkey on your
plate. You wrap your expandable jaws around it and your palate-
forks stuff it down your throat in alternated strokes until the whole
monkey carcass slides down. Finally, only the monkey's tail can be
seen disappearing into your mouth.
72 I THE CONQUERING COLD-BLOODS: A CONUNDRUM
No other land vertebrate today swallows more elegantly than
the snakes. Serpent success—nearly three thousand living spe-
cies—surely owes much to this sophisticated machinery for diges-
tion, which allows snakes to exploit very large prey relative to their
own body size. Human evolution produced a rather dull, simple
jaw apparatus. Our brain size permitted us to compensate by in-
venting stone knives, steel carving sets, and Cuisinarts, so we can
take a whole steer and swallow it, piece by piece. We should ad-
mire how evolution has solved this prey-bigger-than-your-head
problem in snakes with entirely internal adaptations.
How the boa head works.
In the roof of the mouth
the two double-tooth rows
move alternately—the left
side pulls the prey backward
down the throat as the right
side reaches forward, and
vice versa. To expand the
gullet, all the cranial joints
bend outward: The rear jaw
strut swings out, the joint in
each lower jaw flexes, and
the right and left lower jaws
stretch apart at the chin.
MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS | 73
Panzercrocs—the exception that proves the rule.
During the Age of Mammals, very few cold-
blooded reptiles evolved large size and aggressive
habits and challenged the warm-blooded Mammalia.
An exception was the Panzercroc— Pristichampsus—
an eight-feet-long crocodilian that evolved long,
fast-running legs and hooflike claws for land
locomotion and steak-knife—like teeth for killing
and cutting up mammal prey (shown here is the
Dawn Horse, Eohippus). Pristichampsus hunted
during the Eocene Epoch, about 49 million years
ago, but it was very rare, much rarer than big
mammalian predators, proof that cold-bloodedness
was a great disadvantage.
4
DINOSAURS SCORE WHERE
KOMODO DRAGONS FAIL
inosaurs must be viewed as a giant evolutionary system, a vast
D conglomerate of species who shared a common adaptive plan.
No adaptive plan is perfect—neither warm-bloodedness nor cold-
bloodedness, for example, works best all the time. If we probe the
nature of the dinosaurs' success, we can feel out the basic strengths
and weaknesses that existed within the dinosaurian organization.
And that will allow us to understand more about precisely what
kind of animals they were.
Orthodox theory has it that dinosaurs were merely "good
reptiles," essentially scaled-up versions of modern lizards and crocs
whose metabolism was pitifully low compared to mammals'. So we
can begin our inquiry into the nature of the dinosaurs' success by
asking, What are the limitations of the cold-blooded reptiles—where
do they fail today? As we saw in the previous chapter, reptiles and
amphibians do overwhelmingly outscore mammals in total species
count. But it must also be said that there are ecological categories
where the cold-blooded league is almost entirely shut out. If the
basic organization of the dinosaurs really was reptilian, then the
pattern of deficiencies we observe in today's Reptilia should match
the picture we get from the dinosaurian world. But what if the
dinosaurs' successes turn out to be totally different from those of
modern reptiles? What would that mean for the orthodox theory?
If we discover that dinosaurs succeeded where modern reptiles fail,
and vice versa, then such a theory would be totally incorrect.
DINOSAURS SCORE WHERE KOMODO DRAGONS FAIL | 75
Why body temperature is so important. All physiological performance peaks
at one narrow temperature range, and the whole body machinery slows down
when body temperature falls. Many lizards are at peak form at a body
temperature close to a human's—about 98 degrees F. But when body
temperature drops 10 degrees C (18 degrees F), performance drops to half—
running speed is half as fast and digestion takes twice as long. When
temperature drops another 10 degrees C, performance falls to only one
quarter of the peak levels.
Super-giant tortoise— Colossochelys. Today a big Galapagos tortoise can reach
fifty inches long (measured front to back on the bottom shell) and five
hundred pounds. But a few million years ago Colossochelys grew to eighty
inches and four tons or more. Shown here is the profile of a five-hundred-
pounder with rider and, in silhouette, the giant Colossochelys.
In this chapter we can begin by considering the reptilian giants
that came after the end of the Cretaceous, after the end of the
dinosaurs. These cold-blooded monsters evolved during the Age
of Mammals. Their story teaches many lessons about reptilian fail-
ure. Colossochelys, the king of the giant tortoises, presents one such
lesson. Bones from the two-million-year-old sediment of the Si-
walik Hills in India contain fragments of elephant, hyena, hippo,
bear—and of Colossochelys. The fossils of the tortoise king has been
found everywhere in the Old World tropics, from Kenya to Cape
Province to Java (fragments suggest its presence in Florida, too,
during this age). Everywhere it was found, there was an accom-
panying rich fauna of big, modern-type mammals. Complete Co-
lossochelys shells are one of the most breathtaking displays in all of
terrestrial turtledom. They look like fossilized Volkswagen Bee-
tles, enormous bone domes six feet long and three feet high. When
alive and fully grown, Colossochelys dwarfed even the largest giant
tortoise alive today.
DINOSAURS SCORE WHERE KOMODO DRAGONS FAIL I 77
Tortoises are paradoxical reptiles. Their history is a success
story, but they also betray the basic flaws in the economic orga-
nization of the Reptilia. Tortoises constitute a family of the turtle
group, and represent the acme of turtle adaptation to dry-land
habitats. Their feet are super-compact, with short toes and ele-
phantlike cushion pads, and their beaks enable them to crop grass
like a cow (most other modern reptiles are carnivores). Tortoises
aren't an ancient tribe at all; the first tortoise didn't evolve until
the Eocene Epoch of the Age of Mammals, fifteen million years
after the last dinosaur died. So tortoises are one of the very last
big-bodied reptiles to make their appearance. And their dome-
shelled clan scored major ecological successes for forty-five mil-
lion years despite the potential danger from mammalian meat-eat-
ers and plant-eaters.
Giant tortoises could defeat any mammalian predator except
one—man. Because of man, two-ton tortoises are totally extinct
today and even the three-hundred-pounders are very rare, re-
stricted to a few desert islands—the Galapagos off Ecuador and
the Aldabras in the Indian Ocean. The demise of the giant tor-
toises is thus a very recent event for which our own species is
probably to blame. One human hunter couldn't kill a giant tor-
toise easily, but six together could use a branch to tip the tortoise
on its back, then build a fire under its shell, and stew the poor
beast in its own carapace. Human hunters were a very late devel-
opment in the Age of Mammals, and they started multiplying sig-
nificantly only in the last two million years. But once they got going,
our primordial forefathers cut a wide swath through both the Old
World and the New, exterminating dozens of big species of mam-
mal—mammoths, mastodons, saber-toothed cats, giant ground
sloths, to name but a few. And they killed giant tortoises. That
must not allow us to forget the remarkable success of giant tor-
toises up till the advent of human hunters. The best nonhuman
predators couldn't kill off the big tortoises; saber-toothed cats, giant
bears, oversized hyenas, clever wolves, all in their heyday failed to
suppress Colossochelys.
These giant tortoises demonstrate that cold-blooded reptiles
could handle mammalian enemies (nonhuman ones). But their
manner of success also reveals the limitations of the reptile's adap-
tive equipment. Tortoises were "cold-blooded" in the narrow,
78 | THE CONQUERING COLD-BLOODS: A CONUNDRUM
physiological sense of the word: they had very low metabolism
compared to that of a mammal of the same size. A tortoise could
heat up its body tissue only if it had access to abundant solar en-
ergy in the form of direct sunlight or solar-warmed sand or rocks.
Tortoises were also typically reptilian in the small size of their heart
and lungs. They couldn't keep up a level of activity anywhere nearly
as high as a dog, bear, or hyena could. How, then, could the tor-
toise overcome the debilitating effects of its low metabolic perfor-
mance? Armor. Quite simply, tortoises succeeded because they
didn't confront mammals in direct tests of strength and coordina-
tion. Tortoises didn't have to flee the lions the way wildebeest do
today, with a burst of high speed. And tortoises didn't have to de-
fend themselves the way wild boar do, with aggressive counterat-
tacks. When threatened, the tortoise simply pulled in all its
appendages—head, tail, and legs—and waited out the danger, with
vulnerable body tissue withdrawn into its incredibly strong bony
shell. If it had to, a giant tortoise could wait for hours, for days,
even for months, because its low metabolism allowed long fasts.
Tortoises beat mammal attacks by a totally passive defense. There's
a lesson here, one that orthodox paleontologists ignore: When
warm-blooded mammals abound, reptiles can't evolve large size on
land unless very special adaptations permit the reptiles to avoid
direct confrontation.
In the very same tropical woodlands and bush where giant
tortoises flourished for so long, another exceptional reptilian
evolved—the giant land snake. Big snakes labor under the same
limitations as tortoises when faced by mammal predators. Giant
pythons have a low metabolism so they can't keep their bodies warm
if solar heat isn't abundant. Their heart and lungs are low-powered
affairs compared to the typical mammalian design. And snakes can't
compete in prolonged contests of violent activity. How, then, do
giant snakes survive among the lions and hyenas? By stealth and
patience. Giant snakes don't try to compete with hyenas in run-
ning down antelope over long chases. They don't prowl over
hundreds of acres the way lions do. A twenty-foot python glides
silently out of its hole near a waterhole's edge and lies in wait,
concealed by its camouflaged hide and long, low silhouette. Here
again, the low reptilian metabolism permits the giant snake to wait
as no mammal could, for weeks if necessary. Finally, an unwary
DINOSAURS SCORE WHERE KOMODO DRAGONS FAIL I 79
antelope comes to drink and steps too close to the python. In one
moti
on two hundred pounds of snake coil around the antelope's
chest. The snake kills by subtle alterations of its grip, not by vio-
lent contractions. The snake's body musculature can't work a tenth
as hard as a lion's over an hour's time. But by contracting every
time the antelope exhales, the snake's coils can finally tighten into
a suffocating straitjacket.
Big snakes, like big tortoises, deserve credit for their success
in the Age of Mammals. Giant land snakes have hunted mammals
in all tropical continents for the last thirty million years. But we
can see that their success comes only by avoiding mammal-style
hunting tactics. The great serpents succeed by being something a
warm-blooded mammal could never be—a hunter of infinite pa-
tience, with a legless body designed for maximally cryptic loco-
motion and ambush.
Is there any reptile which has successfully challenged large land
mammals for the role of normal, four-footed predator? The Ko-
modo dragon lizard is a possible candidate. Orthodox paleontolo-
gists often point 'to the Komodo dragon as the perfect modern
analogue of the dinosaurs—a big terrestrial reptile that succeeds
in dominating a warm tropical ecosystem. But the. Komodo dragon
is a red herring.
The truth about it helps demonstrate that the dinosaurs' suc-
cess couldn't possibly be the result of a lizard-style metabolism.
Komodo dragons, it is true, can kill the largest land mammals on
Komodo—even adult horses and water buffalo. But the dragon rules
a kingdom of tiny extent. No dragons survive on the nearby big
islands of Java or Sumatra. Dragons swim well and could easily get
to these bigger areas, yet their entire breeding population remains
restricted to a handful of tiny islands. And unlike the tortoises,
these dragons in the past have never extended to the big islands
and mainland areas. There's an obvious explanation for these geo-
graphical limitations.' The dragon succeeds only where it's free from
interference from large mammal predators. Leopards, tigers, and
sun bears prowl the big Indonesian islands, and there were large
hyenas too until a few million years ago. The mainland of South-
east Asia has hosted big cats, wolves, and hyenas in dangerous
profusion. On Komodo Island not one large mammal predator has
Robert T Bakker Page 8
