Robert T Bakker Read online

  hero, that brave, ever-so-clever furry little mongoose who fear-

  lessly confronts the Indian king cobra and its mate, defeating the

  slow-witted serpent by craft and nimbleness and thus saving the

  verandaful of upper-crust English colonialists. I like mongooses,

  but I don't like Kipling's fictitious beast. For one thing, real mon-

  gooses aren't so ingratiating or so stupid as to go down a cobra's

  burrow when it's occupied by its owner.

  But the main reason I'm anti-Kipling is that his stories epit-

  omize an all-pervasive bias in our popular and scientific culture

  against the Big Reptile. Kipling's cobra is a metaphor of size and

  strength without brains or honor. So the mongoose by compari-

  son emerges as a noble and intelligent mammalian furball in con-

  trast to its despicable reptilian foe. Snakes suffer such a terrible

  public image, being forced to serve as the very agent of evil in the

  Garden of Eden and as the synonym for deceit and ambush in

  popular slang. Crocodiles don't fare much better—the one in Peter

  Pan enjoys the dubious distinction of being only slightly less mean-

  spirited than the character it devours, Captain Hook. Big croco-

  dilians, like big cobras, are dangerous, aggressive predators. A

  brackish-water crocodile grabbed the eminent Harvard entomol-

  ogist Philip Darlington by the leg in 1944 on a South Sea island

  while that gentle scholar was studying mosquitoes for the Navy

  48 I THE CONQUERING COLD-BLOODS: A CONUNDRUM

  Spectacular lizard bluff from Australia— Chlamydosaurus. The frilled lizard

  flips its huge scaly collar skin to frighten potential enemies. Growing up to

  three feet long or more, frilled lizards can sprint away at fast speeds on their

  hind legs.

  Department. Darlington kicked his way free after being whirled

  around under water a couple of times, but not a few explorers have

  suffered the complete process crocodiles perform on their prey.

  Cobras and other venom-equipped snakes kill hundreds of village

  people, farmers, and migrants all through the tropics, a yearly toll

  far exceeding that of all the man-eating tigers, lions, and leopards

  together.

  So there is some cause for the human species to be alarmed

  when confronted by a big reptile. However, in our culture, we react

  to these reptilian potential man-killers only with revulsion, not with

  respect. What a difference from the role reserved for mammalian

  MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS I 49

  man-eaters—the lion is so admired for strength and cunning that

  nearly every royal European household placed the tawny beast on

  its coat of arms, and both the Messiah of the Old Testament and

  the Emperor of Ethiopia were hailed as the Lion of Judah. I know

  admittedly little of heraldry, but rest certain that not even the

  shortest-lived Balkan principality adorned its royal crest with a Nile

  crocodile.

  Some of my best friends are mammals. But like most other

  dinosaur paleontologists, I have very mixed emotions about the

  Mammalia as a class in vertebrate history. According to widely ac-

  cepted theories, the Late Cretaceous mammals were among the chief

  ecological conspirators that manipulated the habitats until the Di-

  nosauria were extinct. Most vertebrate paleontologists aren't di-

  nosaur specialists but concentrate on the fossils of mammals instead.

  Any naturalist tends to identify emotionally with the objects of his

  research. Consequently, most mammal paleontologists view the

  Cretaceous extinctions not as a sad finale but as a grand opening,

  the dawn of the Age of Mammals.

  Geologists generally have a fondness for dynamic terminol-

  ogy to label earth processes they study. A pulse of mountain-

  building activity is thus known as a revolution, and the Laramie

  Mountains, folded and raised in Late Cretaceous times east of

  Como, are described as the products of the Laramide Revolution.

  Tacked onto the bulletin board of the student offices in the Uni-

  versity of Wyoming, where Late Cretaceous mammals are a spe-

  cialty, is a poster in the best 1919 Bolshevik style. The earth

  explodes upward, Triceratops tumble over backward stunned into

  extinction, as a giant furry fist thrusts through the land surface

  clutching the banner "Join the Laramide Revolution." And to hear

  the mammal paleontologists talk, after a few pitchers of beer in

  the cowboy bars, it happened that way. With the geological equiv-

  alent of the "Hallelujah Chorus," the irresistible new wave of

  mammals swept aside the old order, replacing the sluggish brawn

  of the dinosaurs with the energetic intelligence of the Mammalia.

  Such talk is annoying. But we few dinosaur specialists huddle to-

  gether at the dark end of the bar, muttering in our beers about

  the insults—insults not just against the Dinosauria, but impugning

  the honor of every turtle, crocodile, snake, frog, and salamander

  as well.

  In European culture, the anti-reptile bias began centuries be-

  50 | THE CONQUERING COLD-BLOODS: A CONUNDRUM

  fore the stratigraphic sequence was discovered. The very word

  "reptile" has a pejorative etymology. Derived from the Latin ad-

  jective reptilis, "creeping," the term originally was applied indis-

  criminately to anything low-down and loathsome—scorpions,

  centipedes, snakes, and lizards. Ever since classical antiquity the

  Reptilia meant roughly the equivalent of "creepy-crawlies." Aris-

  totle, the ancient Greek naturalist, and the Christian philosophers

  who revised and edited his texts, put lizards and snakes low down

  in the scale of animate creation, far below cats, dogs, birds, and

  mongooses. The idea that all of nature could be arranged in an

  ascending scale of complexity and perfection was extraordinarily

  popular among medieval scholars. The principal criterion by which

  any species would be assigned its place on the Scala Naturae was

  how close it came to the unchallenged holder of the top rung, Man

  Himself. According to this view, the Creator, in His wisdom, put

  His best blueprint into production with the human race; the other

  mammals were close, but the scaly, crawling things were far from

  His Own Image. Even when Darwinism cleared away most of the

  creationist mythology from Western science, an evolutionary Scala

  Naturae was easily substituted for the theological one.

  If all the bad-mouthing of reptiles came from bar-hopping

  mammal paleontologists emboldened by one too many beers, or

  the mystic musings left over from the Middle Ages, I wouldn't be

  much disturbed. But when the dean of reptile paleontologists, the

  late Al Romer of Harvard, wrote about the superiority of mam-

  malness over the reptile condition, it made me shudder. Alfred

  Sherwood Romer did some superb and innovative research on the

  hind-limb muscles of dinosaurs in the late 1920s, showing that the

  thighs of duckbills operated more like those of giant birds than

  those of giant crocodiles. But dinosaurs were a minor diversion in

  Romer's long and
distinguished career. He spent most of his field

  seasons, first in Texas, later in Brazil and Argentina, digging up

  mammal-like reptiles, a diverse lot of vertebrates that bridge the

  structural gap between a primitive lizardlike reptile and a genuine

  furry, milk-sucking mammal.

  Romer inherited from his mentor, the magisterial anatomist

  William King Gregory, a passion for reconstructing, step by step,

  the evolutionary pathway that led from the first sprawling reptile

  of the Coal Age, 300 million years ago, to the first bona fide mam-

  mal, something that would look like a tiny 'possum, which emerged

  MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS I 51

  at the end of the Triassic. For Romer and Gregory, clearly the

  proper study for man was Mankind. Therefore the most important

  life thread in geological history was our own, leading backward

  through the Age of Mammals to the tiny, scurrying Mesozoic

  mammals and thence through all the successive stages of mammal-

  like reptiles. Gregory wrote a delightful evolutionary essay for the

  lay person, "Our Face from Fish to Man," which expressed ele-

  gantly the preoccupation with the single evolutionary trackway

  leading upward through the strata to the Mammalia and to Homo

  sapiens. Both Romer and Gregory did study what were perceived

  as evolutionary sideshows—Romer wrote about Coal Age am-

  phibians with flattened, shovel-like heads, and Gregory executed

  definitive treatises about sailfish—but both scholars were true to

  their own class, the Mammalia, when it came to allocating the bulk

  of their labors.

  Romer earned the everlasting gratitude and respect of all rep-

  tilian paleontologists with his Osteology of the Reptiles, a bountifully

  illustrated guide to skulls, limbs, and vertebrae of all the Reptilia,

  including dinosaurs and mammal-like reptiles. Romer's classifica-

  tion of reptiles, which places nearly every known fossil and living

  species in a formal hierarchy, is one of the most widely used among

  herpetologists and paleontologists. When I was a graduate student

  at Harvard's Museum of Comparative Zoology, I was fortunate to

  have a study carrel around the corner from Romer's office. He was

  always ready to talk about his first love, the evolution of mammal-

  like reptiles, at coffee break when he and the other senior pa-

  leontologist, Bryan Patterson, a pioneer in the analysis of Mid

  Cretaceous mammal teeth, sat on the basement stoop with the

  students and staff. For his affability, scholarship, and generous

  support of students, Al Romer is justly remembered as a prince

  among the reptile specialists.

  But Romer did one thing I disagree with, vigorously. He wrote

  that after the close of the Cretaceous, the entire Reptilia became

  second-class, an overaged, unprogressive group that decayed steadily

  in biological importance down to the present time, the evolution-

  ary equivalent of the senile Ottoman Empire gradually losing its

  grip over the eastern Mediterranean after its apogee in the fif-

  teenth century.

  Far from declining senile groups, the Reptilia and their cold-

  blooded cousins, the Amphibia, are today full of vigor, full of spe-

  52 I THE CONQUERING COLD-BLOODS: A CONUNDRUM

  cies, and full of ecological importance. To prove this, one need

  only stroll through any tropical rain forest in today's world. These

  habitats, the richest in vertebrate species, are quite literally crawl-

  ing with frogs, snakes, and lizards—a hopping, slithering, scamp-

  ering horde of highly specialized species whose numbers overwhelm

  those of the supposedly "higher" mammals.

  To evaluate the fortunes of the classes, we need some simple

  system of scorekeeping. One of the best ways to score evolution-

  ary success is to count species. The species is a self-perpetuating

  unit of interbreeding individuals, and two closely related species

  can be proved to be distinct only if they fail to interbreed freely

  in the wild. Most of the time closely related species have slightly

  different ways of making a living. For example, the high plains wolf

  hunted in packs across the prairie, cutting down elk and straggling

  buffalo calves. The coyote, a close relative of the wolf, usually

  traveled in smaller groups, snatching small prey and sneaking in

  to dine on wolf kills after the bigger predators had gone. In zoos,

  coyotes and wolves will mate and give healthy hybrids, but in the

  wild the two usually keep their genes to themselves. Thus, wolf

  and coyote are scored as separate species. When we count the to-

  tal number of species in the Reptilia or Mammalia, we are scoring

  the number of different ecological roles filled by that class. We

  should send those barroom detractors who believe that reptiles are

  a moribund class into the tropical forests, armed with checklists,

  nets, and binoculars. Let the mammal chauvinists count species;

  the results will sober them up. (A genus is a group of closely re-

  lated species; Canis is a genus name, the dog genus, and Cants la-

  trans is the coyote species.)

  If they do their work well, species census takers should score

  fifty nonflying mammals in a thousand-acre plot of the Congo Basin

  or the Burmese lowlands—squirrels, shrews, monkeys, mon-

  gooses, palm civets, antelopes, and elephants. This is a rich fauna

  of furballs by Temperate Zone standards; a New England wood-

  land would score only two dozen species. Now set the census tak-

  ers on the task of scoring every Congolese frog, serpent, and lizard.

  In that same thousand-acre plot the total score for Reptilia and

  Amphibia will be about 180, three times the mammal score. In

  Burma or Thailand the scores will be similar—the "cold-blooded"

  classes win two or three to one. So where is the proof that Mam-

  malia are the best adapted class?

  MESOZOIC CLASS WARFARE: COLD-BLOODS VERSUS THE FABULOUS FURBALLS I 53

  Herpetology is the study of amphibians and reptiles, the name

  being derived from the Greek for snake, herpes, and for learning,

  logos. Biologists, with their fondness for professional nicknames,

  lump all members of these two classes as "herps." An entire rep-

  tile—amphibian census is called a herpetofauna. (Herpes virus, that

  current scare in venereal epidemiology, gets its name from the al-

  leged similarity between how the fever blisters spread and the

  crawling of snakes.) Not only is the herpetofauna of today's trop-

  ics much richer in species than the mammalian fauna, but the

  tropical herps display a veritable riot of adaptive diversity. The

  marine toad of South America is a five-pound warty predator that

  gulps down mice and rats, an ecological function that induces

  farmers to transport the toad all through the tropics to keep down

  rodent populations on plantations. Marine toads are toothless

  hunters but make up for their lack of dental armament by their

  poisonous saliva, which numbs their prey into submission. The big-

  mouthed marine toad sits in ambush along a small mammal trail

 
and makes a short lunge to snap up the unwary rat; a moment or

  two inside the toad's mouth is all that is necessary to anesthetize

  the mammal.

  Among herps, poison is a popular adaptation for defense as

  well as for offense. Arrow-poison frogs of the American tropics

  produce a potent toxin in their skin glands. Some species are dan-

  gerous to handle without gloves—my lab instructor in an under-

  graduate course at Yale fondled a pretty frog, just uncrated from

  Surinam, and was sick for two days. Amazonian hunters dry and

  concentrate arrow-poison frog toxins to smear on the cutting edges

  of their blowgun darts and arrows. One good dose from a dart and

  a thirty-pound monkey falls paralyzed from its treetop refuge.

  Poison even guards New England toads and salamanders—some

  species have enough skin toxins to make a hound dog retch. Wise

  old retrievers learn not to put toads into their mouths.

  The amphibious branch of the herp kingdom is not limited

  to chemical adaptations. Kermit the Muppet frog has made the

  fly-catching tongue famous, but the ability to snap insects by tongue-

  flipping has also evolved in salamanders, the short-legged amphib-

  ians that look like scaleless lizards. Although most amphibian tooth

  equipment is modest by mammalian standards, there is a saber-

  toothed toad: the horned Ceratophrys of the New World tropics.

  54 | THE CONQUERING COLD-BLOODS: A CONUNDRUM

  The sharp-edged upper fangs of a big, adult Ceratophrys can cut up

  the hand of an unwary herpetologist. Ceratophrys also claims the

  distinction of being an armor-plated toad. Embedded below the

  moist outer skin are wide bony plates protecting the shoulders and

  neck. If you grew up in northern New Jersey, as I did, you get

  the impression that frogs are a swamp-bound clan, because watery

  haunts offered the best frog-hunting ground. But most species of

  frog are tropical, and in the tropics fully half of the frog species

  can be land-living as adults, and many climb trees. In the flood-

  plain of the Congo River, three different families of species of tree

  frog clamber about the bushes and forests, snaring insects from

  leaves and bark.

  Amphibians score significant subterranean successes, too. The

  New England mole salamander pushes its way through damp soil