Robert T Bakker

by The Dinosaur Heresies (pdf)

  long and two hundred pounds, big enough to kill unwary tourists. Meat-

  eating lizards twenty times as heavy hunted in Australia in the recent

  geological past (silhouette shows size of the extinct giant compared to a

  modern Komodo Dragon).

  odilians—several lacertilian families are equipped with modest na-

  tatory skills and have shellfish-crunching batteries. Hunting shelled

  prey in the Orinoco and other New World tropical rivers is the

  clam cracker par excellence, the two-foot-long caiman lizard so

  called because its deep tail and armor-studded hide recall the shape

  of the local alligators known as caimans. Bulging jaw muscles and

  nutcracker jaws make the caiman lizard nearly invincible in gus-

  tatory confrontations with Amazonian mollusks.

  Monitor lizards have not limited their guild membership to

  the shellfish-eating clubs. On the Indonesian isle of Komodo is a

  monitor that kills and eats goats, water buffalo, and German tour-

  ists. The story of the Komodo dragon reads like the script for the

  original King Kong (a carefully crafted movie with excellent dino-

  saurs, molded by someone who read Al Romer's research paper).

  Rumors of a great lizard living on a tiny island, a real-life dragon

  called ora by the natives, reached explorers in the late nineteenth

  century. Expeditions brought the first skins and bones to mu-

  seums in 1912, and, for once, legend paled before reality. Up to

  62 | THE CONQUERING COLD-BLOODS: A CONUNDRUM

  eight feet long and as heavy as a lioness, the adult Komodo dragon

  brandishes steak-knifelike teeth—sharp, recurved blades with ser-

  rated cutting edges. Showing the same sagacity found in veteran

  Nile crocodiles, fully adult dragons know their hunting territory

  from years of experience. They know where to lie along hilly game

  trails, awaiting the light footsteps of a deer. Attacks are instant

  successes or failures because the ora has no stamina, and if it misses

  on the first short rush, it has little sustained speed for a long pur-

  suit. When attack succeeds, the cruel rows of slashing teeth cut

  fearful wounds on the rump and thigh of ambushed animals and

  the stricken prey may die of massive infection days later even if it

  manages to break free from the dragon's mouth. Tethered live-

  stock suffer truly terrible cuts across the legs when an ora slinks

  into the compound under cover of the warm Indonesian nights.

  Several humans, both natives and European visitors, have died in

  savage daylight attacks. The victims simply had no warning sign

  that the ora was waiting patiently a few feet from trail's edge.

  Fearsome though the Komodo dragon is, we must go much

  farther south, to mainland Australia, to find the full flowering of

  monitor evolution. The great Australian island continent is a down-

  under, topsy-turvy world in more ways than one. Instead of an in-

  terlocking guild system of small, medium, and large predators, filled

  mostly by mammals, such as we see in the Serengeti, the Austra-

  lian predator guilds feature monitor lizards in many of the roles

  we are accustomed to believe were reserved for the Mammalia.

  The badger role is played well by Gould's monitor, a digging

  predator specializing in buried prey. On other continents the

  brotherhood of furry hunters—weasels, ferrets, and mongooses—

  chase the small prey, but "down under" the long-bodied small

  predators are pygmy monitors. Tourists in minibuses gawk at

  leopards sleeping at midday in Kenyan game parks, but in the

  Australian outback the traveling lizard watcher can catch a glimpse

  of the seven-foot Perentie monitor, draped over a eucalyptus branch

  to escape the noonday heat. Native Aussie mammals take a decid-

  edly second place to monitors in the freshwater guilds, too.

  The greatest lacertilian hunter of this region is, however,

  missing today. A few thousand years ago a monitor Kong stalked

  the Australian landscape: Megalania, a massive half-ton lizard

  predator as big as a Kodiak bear. Fossil Megalania vertebrae and

  MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS | 63

  jaws with monstrous curved teeth were first discovered a century

  ago by pioneering Aussie naturalists and now are known from sites

  across Queensland, New South Wales, and Victoria. With the

  eyewitness accounts of Komodo dragons in mind, one must sup-

  press an involuntary shudder at the image of a resurrected thou-

  sand-pound ora rushing out to tear apart the largest Australian

  mammal.

  64 | THE CONQUERING COLD-BLOODS: A CONUNDRUM

  Dragons and half-ton monsters of Queensland's past should

  not sway us into believing that the vast lizard species-empire was

  built by brute force alone. Lizard adaptations include devices of

  greater subtlety—body ornaments designed for fraud, intimida-

  tion, display, and seduction. The Australian frilled lizard, one and

  a half feet long at most, is of a typical lacertilian temperament, slow

  to bite in earnest even when engaged in vigorous disputes over

  territory or potential mates. There's evolutionary wisdom in such

  restraint. Quarrelsome genes that give their owners a chip on the

  shoulder will get weeded out of the population, if constant brawl-

  ing leaves the lizard scarred, crippled, and too exhausted to breed.

  Darwinian processes have operated on the frilled lizard to concen-

  trate genes whose results are more theatrical than rowdy. Lining

  Two-ton dragon lizard of

  ancient Australia. Fifteen

  feet long and as heavy as a

  bull rhinoceros, the extinct

  Megalania hunted giant

  kangaroos during the

  Pleistocene Epoch of the

  Age of Mammals, a few

  hundred thousand years

  ago. A scaled-up version of

  today's Komodo Dragon,

  Megalania died out quite

  recently, by geological

  standards, and for reasons

  that are totally unknown.

  MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS

  65

  the lizard's mouth is tissue of the most brilliant vermilion. Hang-

  ing limp around the neck is a wide collar of folded skin. When the

  lizard must assert its presence, a direct biting attack is eschewed

  in favor of a grand thespian display: the mouth pops wide open,

  unveiling a sudden flash of red on palate and tongue, and the col-

  lar snaps erect, spreading a scaly corona about the neck like the

  frill around the Dutch Masters, increasing the apparent head size

  sixfold. Hissing and lunging forward, the frilled lizard goes through

  its act, a gaudy vaudevillian bit of behavior which transforms the

  little inoffensive lizard into an animated trick-or-treat mask.

  Body ornament for intimidation produces some of the most

  decorative vertebral columns in lizardom. In most vertebrates the

  vertebral spines are strictly utilitarian and nonornamental. The bony

  prongs rise up from each vertebral segment to provide leverage

  for the back and neck muscles (the series of bumps down your

  back, between th
e shoulders, are the tops of vertebral spines). But

  the Australian water lizard grows spines so long they project far

  beyond the muscle contours and extend upward like a picket fence

  embedded in a thin sheet of tough skin. This lizard's intimidation

  technique, like that of most species, is broadside bluff. Turning

  sideways to its foe, the water lizard puffs itself up, standing as tall

  as possible, showing off its vertebral sail to best advantage, trying

  to prove that it is bigger and nastier than its rival. If your rival

  looks taller, then he might be bigger and stronger. This simple mes-

  sage is encoded in most lacertilian brains and plays out automati-

  cally during disputes, controlling the lizard's fight-or-flight response.

  South American riverside forests are home for one of the best

  broadside bluffers, the Jesus lizard. Here the males sport among

  the most flamboyant vertebral crests known anywhere today. Sheets

  of bone protrude from the head and the picket fence rises from

  the torso to make the skinny lizard body look three times as big

  as it really is. The name "Jesus lizard" doesn't come from the puff-

  and-bluff display, but from the speedy getaway performed by the

  lizard when its tiny brain snaps over to the flight mode. Very long

  in the hind legs, the Jesus lizard can sprint so fast for a few dozen

  yards that its momentum carries it across the surface of lake or

  river, the long-toed strides propelling it far beyond the shore. After

  its walk-on-water dash the lizard can sink out of sight, a bewilder-

  ing performance for most enemies.

  66 | THE CONQUERING COLD-BLOODS: A CONUNDRUM

  Seventeen miles per hour lizard—

  Crotaphytus. Up to a foot long, this

  resident of our western deserts hits

  top speed in a hind-legs-only

  bipedal stride.

  All today's cold-blooded speed records are held by lizards. The

  best lacertilian sprinters are long-legged bipeds, species that at high

  speed tuck their arms under the chest and stride on hindquarter

  power alone. In our own American West the mountain boomer, a

  short-bodied, wide-headed predator that gulps down big desert bugs

  and other lizards, has been clocked at eighteen miles per hour.

  Lizard feats of arms and legs span the entire range possible for a

  land vertebrate, a complete evolutionary decathalon: burrowing by

  wormlike amphisbaenid lizards; sand-swimming by Kalahari skinks;

  snakelike grass-slithering by legless glass lizards; crocodilelike

  swimming by monitors; leaf-leaping by anolis lizards (Florida cha-

  meleons); claw-propelled digging; bipedal sprints; and the incred-

  ible slow branch stalk by the Old World tree chameleons. And there

  are even some lizards that can glide, using rib-supported wings.

  Walking narrow branches is a tough high-wire act for most

  lizards, difficult to master because the basic lacertilian posture is a

  sprawl, with elbows and knees held far out beside the body and

  the paws held far apart. Gripping a narrow branch is awkward with

  such a wide-track gait. The prizes for the successful branch walker

  are enticing: hordes of insects and other juicy prey teem among

  the leaves, twigs, and stems. The Old World chameleons have

  solved this problem with a suite of limb adaptations rarely matched

  MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS | 67

  elsewhere. Most lizards have broad chests, which separate left and

  right shoulder sockets widely. Chameleons have deep chests, very

  narrow from side to side, like that of a cat. So the chameleon arms

  can swing fore and aft directly under the body. And the chame-

  leon's forepaws can grip the narrowest of perches. Most lizard hands

  are rather crude five-fingered devices incapable of a precise grip.

  Chameleon hands are cleft—two fingers are separated from the

  other three at the wrist—and the chameleon can use the two as a

  sort of scaly thumb for gripping a branch. Hind limbs are similarly

  cast into a narrow-striding, gripping mode. With four precision

  grippers and a narrow stride, the true chameleon on the hunt makes

  all the slender vines and branches of the tropical forest unsafe for

  butterflies and beetles.

  Our own mammalian order, the primates, prides itself on

  hand—eye coordination; monkeys, apes, and man are all good ma-

  nipulators. But no mammal can rival the chameleon for eye—tongue

  coordination. The tongues of chameleons are explosive devices,

  lying loaded on the floor of the mouth, ready to fire forward as

  elongated, muscle-propelled missiles armed with a sticky, bug-

  catching warhead. Missile warheads are useless without their guid-

  68 I THE CONQUERING COLD-BLOODS: A CONUNDRUM

  The Malay flying lizard,

  Draco. About six inches long,

  nose to tail tip.

  ance systems, and the chameleon has a stereoscopic rangefinder

  and fire-control apparatus unique among vertebrates. Each cha-

  meleon eye is mounted in a scale-studded turret which can move

  independently, scanning the branches for insect targets. Once a

  beetle is located, eyes switch to attack mode—both turrets lock

  their stare forward on the target. Eyes feed the brain target data,

  distance, bearing, target size—the fire-control computations are

  swiftly made, automatically, without conscious thought, zap!—the

  tongue muscles contract, hurling the bony tongue base forward and

  Best tongue show in lizarddom. Chameleons are

  lingual sharpshooters, firing their extensile tongues

  twice their body length to catch insects. This genus

  is Microsaura, one of the smallest varieties, only a

  few inches long head to hips. Other species reach a

  foot or more.

  squeezing the tongue warhead at great speed out of its contracted

  state. Another Congolese beetle is swept into the high-tech cha-

  meleon jaws.

  Lizards labor under the disadvantage of being the least pub-

  licized reptile clan, but their close kin the serpents bear the worst

  prejudice handed out by human society. This is unjust. Snake

  anatomy contains the most clever and intricately efficient feeding

  apparatuses to be observed anywhere among land vertebrates. Our

  human problem begins with our adaptive table manners; we're not

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  accustomed to admiring creatures that can swallow something larger

  than their heads. All human parents, from Boston mayors to

  boomerang-wielding natives, warn their children not to stuff too

  large a hunk of food in their mouths. Human gullets are small and

  have only modest capacity for expansion. It's ecologically adaptive

  for human parents to discourage gulping big pieces of food, be-

  cause choking is an uncomfortably common agent of human mor-

  tality.

  Snakes, however, cannot chew. The evolutionary path they

  chose early in their career required unusual adaptations for swal-

  lowing huge hunks of food: (1) snakes are all predators, subsisting

  mostly on live prey; (2) they ambush by stealth, not by moving

&n
bsp; about scanning for victims, hence snakes don't meet a lot of po-

  tential prey each day; (3) therefore snakes have to make the most

  of each opportunity and should attack the largest potential prey.

  The Darwinian processes that favor the selection of big prey have

  also equipped serpents with their special organs for throttling and

  stabbing. Pythons have a crushing attack. They coil around large

  victims, constricting whenever their prey exhales, suffocating it

  slowly and with an economical expenditure of force. (Contrary to

  popular myth, big constrictors don't crush bones and pulp their

  victims into pudding; just enough force to asphyxiate seems to be

  the rule.) The poison attack evolved by several other snake fami-

  lies allows them to inject their venom with surgical precision

  through hollow fangs. Once the big victim is subdued by the con-

  strictor's embrace or by a dose of poison, the snake must swallow

  it whole, because no snake has cutting teeth suitable for slicing

  the victim's body into bite-sized pieces.

  Here is the nub of the problem: Snakes are long, narrow beasts

  with heads of very small width compared to many lizards and most

  frogs. Such a small, narrow head is a necessary component of the

  snake's fundamental mode of movement, sliding through narrow

  paths and down burrows. A giant tropical toad may have a mouth

  nearly as wide as its body is long, and so it can gulp down prey

  nearly as large as itself. But the poor puff adder, having success-

  fully brought down a monkey offering enough meat to keep the

  snake going for a month, now faces an item of food at least twice

  the width of its own mouth. The solution to this gustatory di-

  lemma has generated the most elegant cranial architecture in land

  vertebrates.

  70 | THE CONQUERING COLD-BLOODS: A CONUNDRUM

  How to swallow something larger than your head—snake-style. A view

  directly into the wide-open mouth of a boa constrictor. All the upper and

  lower jaw bones are loosely connected by elastic ligaments, and each side of

  the skull has not one but two rows of curved teeth.

  A great snake in the act of swallowing something larger than

  its head presents a marvel of reptilian engineering. The snake ma-

  nipulates its prey's body with its mouth, until it faces the prey's