that resemble frying pans. The long snout looks like the handle,
the squarish cranium the pan. These Meerkrokodiliers, as our Ger-
man colleagues call them, are not the lineal descendants of the sea
crocodiles of the Jurassic, but are a new oceangoing group de-
scended from Jurassic freshwater crocodiles.
Opportunism again. When the Jurassic sea crocodiles were
exterminated by the Early Cretaceous disturbance, an ecological
opportunity presented itself to any reptile that could swim and catch
fish and that could adapt to fully oceanic conditions. And so the
rivers gave to the sea a new player for the reorganized Cretaceous
marine systems. All through vertebrate evolution the flow has been
mainly in this direction—from the fresh waters to the ocean shore
to the high seas. Just so did the rivers give us the first whales some
fifty million years ago, descendants of some river-haunting preda-
tory mammal, one of the many mammalian lines that were rushing
in to fill the empty niches left by the final extinction of the dino-
saurs and sea reptiles.
The Benton Sea supported a wonderful menagerie of Creta-
ceous oceanic reptiles. In Colorado, Benton-age shales produced
a nearly complete elasmosaur skeleton, a fast-cruising type of ple-
siosaur that slipped through the tropical Late Mesozoic water with
the propulsive power of four narrow, tapered flippers, snatching
prey with its snakelike neck.
At Como, Othniel Charles Marsh's men found an armor-plated
nodosaur lying on its back embedded in the now hardened depos-
its left by the mud on the sea floor. Finds like this were excep-
tions to the rule that dinosaurs did not go to sea. Was the nodosaur
swimming in the Cretaceous shallows before it met its end? Or is
it the remains of some terrestrial individual that died a death on
dry land and then, in the form of a dried-up carcass, was washed
out to a final oceanic resting place by flood-swollen river waters?
The problem of oceangoing nodosaurs is especially perplexing be-
cause the Como carcass, upside down at the bottom of the Benton
Sea, is not an isolated instance. Nodosaur carcasses lying on their
backs cropped up in marine beds in Kansas in 1909 and several
times since in similar sedimentary circumstances.
40 I THE CONQUERING COLD-BLOODS: A CONUNDRUM
There are no duckbill dinosaurs at Como, because the Ben-
ton Formation is too old. The duckbill dynasty began past the
midway point of the Cretaceous. A short trip east through the
Laramie Mountains to Red Bird places us in duckbill country, the
Lance Formation of the later Cretaceous, a mass of pale brown river
sandstones with interbedded chocolate-colored mudstones, some-
times faintly discolored by the pink of oxidized iron. Nearby is
Lance Creek, supposedly named for the cavalry lance carried by
mounted Sioux warriors.
Lance outcrops give their name in turn to the final terrestrial
epoch of the Cretaceous world, the Lancian Faunal Age—a time
that witnessed the adaptive deployment of the most exotic and bi-
zarre skulls of all the panoply of dinosaurs. Triceratops was here,
the scientific etymology "three-horned face" being, in this case, an
excellent shorthand description of this formidably armed herbi-
vore. Over each reinforced eye socket grew a horn of such size as
to threaten even the largest Tyrannosaurus rex. In life these weap-
ons were long, sharp, and deadly because the underlying bone was
covered with a horny sheath like that surrounding the cores of cattle
and buffalo horns today. Out on the snout was a third, midline
horn, and below it a toothless beak, deep and powerful like that
of a multi-ton snapping turtle. This too was clothed in life by a
shiny hornlike substance, giving the beak an ever-growing, self-
sharpening edge. Plant-eater though it was, Triceratops could turn
the branch-cutting apparatus of its beak into a defensive set of
nippers strong enough to inflict wounds on even the largest an-
tagonist.
Truculence, nippers, and horns seem to go together. Today,
the great Indian one-horn rhino can turn into the terror of the
mahouts as it charges domestic elephants. The largest Triceratops
weighed nearly ten tons, bearing horns that, fully sheathed, were
four feet long. No species that has ever evolved on land could
withstand the full charge of such an animal.
Duckbill dinosaurs did not display the deadly cranial arma-
ture worn by Triceratops. Nonetheless the duckbill group enjoyed
an extraordinary evolutionary flourish of head ornaments and ad-
aptations in the final days of the Cretaceous. The term "duckbill"
is a biomechanical misnomer. True, the duckbill dinosaurs did have
wide, flattened beaks, which at a distance vaguely resembled that
of a mallard. However, the edges of their beak were turned down
WYOMING REVERIE: MEDITATION ON THE GEOLOGICAL TEXT I 41
into a sharp, cookie-cutter edge, sheathed in life by a self-sharp-
ening horn. The entire apparatus was a leaf-cropping adaptation
for slicing off mouthfuls of tough fodder in a single bite. Duckbill
teeth were one of the true marvels of mastication, cited every-
where in texts on dental evolution. Instead of one single row of
teeth along each jawline, the duckbill had multiple rows, which
combined to make a leaf-shredding surface equivalent in function
to an ever-sharp carrot grater. No evolutionary device has ever
evolved to masticate tough plant fiber more effectively than the
dental shredder of the duckbills.
Although the feeding devices of the duckbills have provoked
no end of wonder among paleontologists since the first duckbill
was excavated in the phosphate fertilizer mines of New Jersey in
the 1850s, it is the array of duckbill head ornamentation that stirs
up the most puzzlement and debate. The common Lance Creek
duckbill, Edmontosaurus, seems built to a no-nonsense, practical
design. Its skull houses the beak, teeth, jaw muscles, and sense
organs. But close relatives from Alberta and New Mexico show
no such restraint in their headgear: Parasaurolophus carried a dou-
ble-hollow bony tube like a trombone slide on the back of its skull;
Saurolophus had a solid bony spike in the same position; Hypacro-
saurus sported a thin-shelled bony crest rising high above the full
length of its forehead and skull table.
This cranial exuberance at first glance reminds one of all the
head appendages some families of birds employ to show off in pre-
mating rituals, such as the combs of roosters, the domed fore-
heads of some species of geese, the crests of cassowaries. And
perhaps here the first impression is the correct one. Dinosaurs had
to have sex, although one would never guess so from the scrubbed
Sunday school versions of dinosaur biology presented in the chil-
dren's books. Sex and pre-mating ritual are parts of the basic evo-
lutionary game: genes that produce adaptations which succeed in
increasing their representation in the next generation are the ge
nes
that survive. The genes of the dinosaurs must have played by the
same statistical rule. If a garish head crest and some accompanying
behavior, such as a strutting head-bobbing walk, made the male
Parasaurolophus more attractive to the female and more intimidat-
ing to his rivals, then eventually the genes responsible for this
equipment and its use would be fixed in the species. For most of
42 | THE CONQUERING COLD-BLOODS: A CONUNDRUM
this century, American paleontologists avoided sexual interpreta-
tions of dinosaur structures.
The European contemporaries of American scientists weren't
so prudish. The Swedish paleontologist Carl Wiman hired an
American dinosaur hunter, Charles Sternberg, to quarry and crate
duckbills from New Mexico and horned dinosaurs for the Swed-
ish Museum at Uppsala. Sternberg sent a magnificent Parasauro-
lophus to Wiman, who noticed that the double-hollow tube of the
crest was simply a U-shaped elaboration of the air tract from its
nostril to its windpipe. Wiman was a broadly educated naturalist,
well aware of the multitudinous ways in which modern species of
bird, frog, and mammal make love by making noise—hooting,
the U-tube in the duckbill's air passages? It looked like a trom-
bone, it was a trombone! If the duckbill inhaled or exhaled with
force, the U-tube would be a resonating chamber, enriching the
tone and amplifying the noise. Hollow crests in other duckbills also
The trombone duckbill, Parasaurolophus
WYOMING REVERIE: MEDITATION ON THE GEOLOGICAL TEXT I 43
connected the throat to nostrils, and the variety of crest shapes
from species to species would certainly produce a variety of hoots,
wheezes, and amplified snorts specific to that species.
Even crestless duckbills like the Lancian Edmontosaurus had
highly arched palates, and the vaulted roofs of their mouths could
be used to modulate tones and increase decibel levels. And the
crestless duckbill probably had additional sound equipment in its
nasal compartment. The bone around the outer surface of the ed-
montosaur must have housed nasal diverticula, pouches of skin
opening into the main nostril channel. Horses have similar diver-
ticula, though of modest size compared to the edmontosaur's. Watch
a stallion snort: The diverticulum shudders with pulses of forced
air from the lungs, the sound controlled by sphincter muscles in
lip and nose. The Late Cretaceous evenings in southeastern Wy-
oming must have been punctuated by reverberating snorts as the
duckbills, driven by their genes, strove to impress each other.
The final hours of the Cretaceous are not to be found at Como
or Lance Creek. This most profound of land extinctions may be
witnessed if we go north, through Wyoming to northern Montana,
to Hell Creek. Here, better than anywhere else in the world, the
stratigraphic pile records in detail the events surrounding the ex-
tinction of the ultimate Great Dying.
Any attempt to analyze the events of the extinction of the di-
nosaurs runs into the fundamental difficulties that hinder the in-
vestigation of any of these mass murders of species. Most fossil
bones owe their preservation to quick burial by sediment right after
the death of their owner. But generally most spots in the terres-
trial biosphere suffer erosion, not deposition. Only in slowly sink-
ing basins, pieces of real estate hundreds of miles across, can we
hope to see a long interval of time recorded by the preservation
of fossils. If a broad, basin-like valley was near sea level, its rivers
and estuaries could blanket the landscape with layers of mud and
sand every flood season. The very weight of these blankets of mud
and sand tended to push the land surface as if the basin itself were
a sagging rubber bowl. If the sinking of the valley's surface kept
up with the rate of buildup in the blankets' thickness, then the
pile of sediment grew thicker and thicker, even though the aver-
age height of the land above sea level remained the same. The re-
sult, after ten or twenty million years, was a thick sandwich of
sediment that might reach a vertical height of five miles.
44 I THE CONQUERING COLD-BLOODS: A CONUNDRUM
Sinking basins don't sink forever. If they did, it would be
possible to read the entire fossil record of life from bottom to top
in one mine shaft sunk into a single valley. Instead, to understand
the changing habitats of the end of the Cretaceous, it is necessary
to hop from state to state, basin to basin, in order to piece to-
gether the disjointed narrative in the sediment, much as silent-movie
buffs might try to reconstruct an entire lost feature by splicing
fragments of film found in a dozen different studio storage vaults.
The fragment of the story recorded at Lance Creek carries us
late into the Cretaceous, but not to the very end. In Hell Creek,
Montana, and nearby Bug Creek, however, there is a sedimentary
section, rich in fossils, that passes right through the last moments
of the Cretaceous and continues into the next epoch, the Paleo-
cene. Even at Bug Creek the strata do not record a year-by-year
surveillance of the scene of the crime that would allow us to catch
the perpetrator in the very act of extinction. In the best of basins,
fossils weren't preserved every year, or even every hundred years.
to cover them, and these events didn't happen except at long in-
tervals, perhaps hundreds or thousands of years apart. Even when
buried, bones weren't necessarily safe. Acid groundwater might
percolate through the sand, dissolve the bone mineral, and leave
nothing behind but a gross, misshapen carbon stain where a duck-
bill's skull once lay. Or a sudden shift in a river's course could erode
part of the sedimentary layer it had deposited years before, and
all the entombed bones would go tumbling down the new chan-
nel, breaking into irretrievable fragments. Paleontologists are
grateful to streams for their blanketing of bones, but most streams
also cannibalize. In one century they lay down deposits over the
valley floor, in the next they might chew through their own sedi-
mentary handiwork, churning and cracking buried bones and eras-
ing the very fossil record they have previously preserved.
The movie-film analogy allows us to visualize the frustrating
process of investigating the Cretaceous. Instead of a continuous
film, one frame a year for each of the last million years of the
Mesozoic, only short bursts of film remain intact, each a few dozen
frames together, separated by hundreds of feet of totally missing
footage. If something important, like the final extinction of dino-
saurs, happened suddenly, within a few years, we wouldn't have a
prayer of catching the deed in the film clips of sediment.
WYOMING REVERIE: MEDITATION ON THE GEOLOGICAL TEXT I 45
The best detective stories are those that comma
nd our rapt
attention to every scrap of clue, so that we can solve the crime in
the final chapter, just before the sleuth announces the identity of
the murderer. Dinosaur extinction attracts the best of paleonto-
logical detectives. Up to Bug Creek and Hell Creek they go, dig-
ging quarries, running sediment through fine sieves to sift for the
tiniest of bones and teeth. But much of the mystery remains. Only
a few facts are clear. The final dying was sudden, compared to the
immense length of the history of the dinosaurs: It took no more
The Mammalia take over. Four million years after the dinosaurs died, the
mammalian hordes evolved into big tuber-digging herbivores, like
Psittacotherium (at left), and big predators, like Ancalagon (at right).
46 I THE CONQUERING COLD-BLOODS: A CONUNDRUM
than two million years—maybe much less—to exterminate all the
Cretaceous dynasties. And there were opportunists waiting around
for the dinosaurs to die: small, furry, insect-eating, berry-chewing
mammals scurrying around the underbrush, fidgeting about,
grooming their whiskers. As the dinosaurian clans were thinned
out, with the extinction rate exceeding the production rate of new
species, these Late Cretaceous furballs expanded their ecological
sphere of influence. The fossils show new types of small, mam-
malian plant-eaters and insectivores blossoming in Montana at the
very time the evolutionary fortune of the dinosaurs was sinking
into its final, irrevocable decline. Passing upward through the sed-
imentary pile in Montana, exposed now in dry gulches, we can see
the shifting census of evolutionary success. The mammals were di-
versifying rapidly near the very end of the Cretaceous, and dino-
saurs dwindled until a level is reached in the layer of mud and sand
through which no species of dinosaur passed. This layer marks the
end of the Lancian Epoch, the end of the Cretaceous, the end of
the Mesozoic. This time the dinosaurs would not recover.
WYOMING REVERIE: MEDITATION ON THE GEOLOGICAL TEXT | 47
3
MESOZOIC CLASS WARFARE:
COLD-BLOODS VERSUS
THE FABULOUS FURBALLS
henever I read Kipling's "Rikki-Tikki-Tavi," I root for the
w
V snake. There's something very irritating about the story's