twenty million years—far longer than the genera of dinosaurs or
mammals lasted in Megadynasty III and IV. Moreover, in Mega-
dynasty I the ecological niches werf undersaturated, because new
types did not develop quickly. On the dry floodplains there was
only one genus of large vegetarian, Diadectes, and only the one big
predator, Dimetrodon. Such an impoverished system appears very
underpopulated compared to most dinosaur habitats. And unlike
the dinosaurs, which suffered several mass extinctions, nothing
similar ever struck the ecological community ruled by Dimetrodon.
Genera went extinct one by one, with new genera entering ac-
cording to a rather leisurely schedule.
When the first protomammals appeared, Dimetrodon and the
entire somnolent world of Megadynasty I passed away. This was
an extraordinary upheaval, which I call "the Kazanian Revolu-
tion"—eventually it will set the stage for the appearance of the
dinosaurs. The Kazanian Epoch is named from the old Russian
province of Kazan, west of the Ural Mountains. There, the most
ancient protomammals are found in the red-stained sediment and
THE KAZANIAN REVOLUTION: SETTING THE STAGE FOR THE DINOSAURIA | 409
yield their bones to the careful spadework of Soviet paleontolo-
gists. The Kazanian families burst into the evolutionary drama with
unprecedented energy. They started out as slender-limbed, wolf-
sized predators, and rapidly expanded their empire into nearly every
role in the ecology, sweeping away the ancien cold-blooded regime.
Within a few million years Kazanian protomammals had taken over
all the carnivorous roles—large, medium, and small—nearly all the
herbivorous roles, and produced dozens of small, insect-eating
species as well. Never before had the ecosystem witnessed such a
spectacular proliferation of new species from a single family. The
Kazanian Revolution was the first terrestrial example of explosive
"adaptive radiation."
Right from the beginning, the Kazanian protomammals stuffed
whole clusters of species into each role. The best preserved of these
are found in the red beds of the South African Karoo and display
a richness far greater than anything recorded before. Protomam-
mals produced four different families of predators, with eight or
ten different species, to prowl through the floodplains and forests
of the Karoo. Biggest of them were the dome-headed anteosaurs,
the size of polar bears, with thick, bony buttresses over their eyes
for head-butting in the mating season. Anteosaurs were armed with
a great row of long teeth that meshed together to clamp down on
prey. Predators from other families, the size of wolves and jag-
uars, displayed a wide variety of lethal devices for dealing with their
prey. Plant-eaters were numerous, too. Five families and a score
of species munched their way through the greenery of the ancient
Karoo.
Why did these Kazanian protomammals evolve so quickly?
They produced new species at very heated rates, and adapted them
very speedily, so that most lasted only a few million years before
they were replaced. The evolutionary tempo of the Kazanian ap-
pears as fast as that of our own Class Mammalia during the Age
of Mammals. Yet they suffer from the same bias maintained against
the dinosaurs. They included some large species—up to one or two
tons—but paleontologists dismiss those as behemoths of low
metabolism that had to use their bulk to keep them warm. As a
student at Harvard, I became interested in these Kazanian proto-
mammals because they displayed the same evolutionary vigor I
discerned in the dinosaurs. And I began to suspect that both they
and the dinosaurs had been warm-blooded.
410 | DYNASTIC FRAILTY AND THE PULSES OF ANIMAL HISTORY
First explosion of the warm-bloods! Before the Kazanian Epoch, the
evolutionary style was slow and spaced out. Species lasted for many millions
of years and there was only one common large predator family and only one
common large plant-eating family in most habitats on the land ecosystem. But
suddenly the Kazanian protomammals burst upon the evolutionary stage and
in a few million years branched out into five separate meat-eating families
and four separate plant-eating families. Habitats were filled to overflowing
with fast-evolving species. And soon after this great evolutionary boom, there
was the first gigantic crash—a mass extinction that wiped out most of the
Kazanians. A few protomammals survived, and a new evolutionary bloom
followed—the Tartarian radiation. (Each head portrait represents one family
in this chart.)
A Kazanian scene: Trochosaurus, a protomammal, attacks an herbivorous
pareiasaur.
My desire to study the Kazanians firsthand took me to Cape
Town, South Africa, where 90 percent of the specimens are housed.
My hypothesis was that if the Kazanians had been the first warm-
blooded animals, then they would have required a great deal of
food per year, and therefore the predators would be rare. Large
samples of fossils are needed to prove such an hypothesis. And
fortunately for me, one man, Liewe Dirk Boonstra, had poured an
entire lifetime into excavating the Karoo and carefully sorting the
species. Almost singlehandedly, he had built a detailed picture of
the Kazanian world. His storehouse of fossils left little room for
doubt: Although the Kazanian predators had been diverse and fast-
evolving, they had been rare compared to the plant-eaters, very
412 | DYNASTIC FRAILTY AND THE PULSES OF ANIMAL HISTORY
rare. The total body weight of all the Kazanian predators repre-
sented only 7 percent of the total for the entire fauna. This was a
predator-to-prey ratio as low as in some mammal faunas, strong
support for the case for warm-bloodedness.
I did not wish to rely on that argument alone, so I sought cor-
roboration from a totally separate line of evidence—the microtex-
ture of bone. At the very same time I was examining the
protomammals in Boonstra's collection, Armand de Ricqles was
cutting bone samples from them in Paris. Each of us was doing his
work unknown to the other, but both of us suspected something
special was to be learned from the Kazanians. De Ricqles pub-
lished his results in Annates de Paleontologie; I published mine in
Scientific American. Our separate lines of detective work con-
verged on the same conclusion: The Kazanians had been a new
phenomenon in the history of life, the first vertebrates whose bone
microtexture indicated fast growth, the first ecosystem whose
predators were rare, the first with a warmed-up metabolism.
Consistent with a warm-blooded metabolism, the Kazanian
therapsids would have developed a more sophisticated design in
the mechanics of their limbs. The older style limbs of the Coal
Age wouldn't have been adequate for warmed-up metabolic needs.
If de Ricqles and I were correct about Kazanian metabolism, ma-
jor adaptive remodeling should have been manifest in limb joints,
adaptions for faster speeds. On this point, Boonstra once again
supplied most of the preliminary material; his excavations had re-
covered literally dozens of good skeletons, and he had published
precise diagrams of every limb from shoulder to wrist, hip to an-
kle. It turned out that both the shoulder and hip sockets of the
Kazanians were much deeper than any found in the Coal Age. They
had obviously been built to withstand much more powerful pres-
sures from the muscles of the limbs. The knee joints indicated the
Kazanians were designed for fast, bouncy gaits—the crests for
supporting the extensive muscles of the knee were massively de-
veloped. When those muscles contracted on a one-ton protomam-
mal of the Kazanian, the great beast would surely have bounded
forward into a lively run. Clearly, the shuffling age of the Carbon-
iferous was over; the Age of Trots had begun.
All the pieces of the Kazanian puzzle seemed to fall into place
with unusual ease. Warm-blooded metabolism and fast-growing rates
THE KAZANIAN REVOLUTION: SETTING THE STAGE FOR THE DINOSAURIA | 413
were consistent with the overall picture of fast evolutionary rates.
They were also corroborated by the remodeling of limbs for faster
moving speeds. And finally, they were consistent with the new
sexual vigor implied by the head-butting armament commonly
found. All of these things implied the Kazanian protomammals had
extra energy to burn.
In Kazanian times, the Karoo experienced cool winters be-
cause it was closer to the South Pole than it is now. To remain
active all year round, the smaller animals might well have needed
some kind of insulation. Orthodox paleontology insists that hair is
a uniquely mammalian invention, the adaptive badge of our own
Class Mammalia. Several dissenters have however suggested that
perhaps hair evolved long before the first true mammal appeared
in the Late Triassic. Perhaps hair did evolve at the very beginning
of warm-bloodedness, back in the Kazanian, fully forty million years
before the earliest true mammals. Maybe our picture of the Ka-
zanians should include shaggy protomammals stalking their prey
through a winter snowstorm, hot breath steaming from their nos-
trils.
A last, quite important, piece of the evolutionary puzzle also
falls easily into place concerning the Kazanian: mass extinction.
Warm-blooded protomammals would of course have been vulner-
able to catastrophic die-offs. And exactly such a disaster did cut
most of them down. After a reign of five to ten million years, nearly
all of them went extinct, leaving only a few surviving groups. This
disaster was the earliest truly mass extinction in the history of land
ecosystems. The Kazanian protomammals paid the price of their
warmed-up metabolism.
In the badlands of the Karoo Basin and the outcrops north-
west of the Urals, the end of the Kazanian and the beginning of
the Tartarian Epoch are clearly marked. At the dawn of the Tar-
tarian, the surviving protomammals rebounded into ecological
dominance, exploding into a riot of new species, genera, and fam-
ilies. Dicynodonts ("two-tuskers") replaced the extinct domeheads
as the big plant-eaters. Saber-toothed gorgons replaced anteosaurs
as giant meat-eaters. This second wave of protomammals pro-
duced a very rich array of species, just as the first had. And they
evolved quickly.
Were the Tartarians also warm-blooded? Almost certainly. De
414 | DYNASTIC FRAILTY AND THE PULSES OF ANIMAL HISTORY
Ricqles found a mammal-type bone texture in all of the Tartarian
protomammals. And I found very low predator quantities. Sam-
ples from both the Karoo and from Russia revealed that predators
made up only 5 to 12 percent of the total preserved fauna.
The high metabolism of the Tartarian protomammals is also
attested by the sudden collapse of their system. Their dominance
lasted only a few million years before it crashed into a mass die-
off corresponding with the very end of the Permian Period.
During the next epoch, the Scythian, yet another wave of proto-
mammals evolved to replace the vanished Tartarians. This third
wave also exhibited all the signs of warm-bloodedness. Appar-
ently, once it had evolved, the genie was out of the bottle, never
again to be imprisoned. After the first takeover by warm-blooded
families in the Kazanian, each new wave of animals of Megady-
nasty II displayed all the marks of high metabolism—fast-growth bone
structure, ecosystems where predators were rare, and vulnerabil-
ity to mass extinction. And the most important thing to remember
World geography in the
Kazanian Epoch. All the
continents were jammed
together in one mass, and
the climate in the far north
and far south had cold
winters. The Karoo
protomammals must have
had some sort of warm-
blooded adaptation to cope
with the weather.
THE KAZANIAN REVOLUTION: SETTING THE STAGE FOR THE DINOSAURIA | 415
about those three waves of protomammals is that they existed long
before the appearance of the first dinosaur.
The disaster that wiped out most of the Tartarian groups at
the end of the Permian Period was also an opportunity for new
families to expand their ecological roles. One such group con-
sisted of protomammals that survived from the Tartarian. Several
dicynodonts survived to produce a new adaptive radiation in the
Scythian and flourished tremendously right down through the rest
of the Triassic Period. Two new groups entered the role of large
predator and herbivore. One of these was the cynodonts, with their
doglike faces. This group had been limited to a small body size in
Tartarian times. But extinction of all the Tartarian top predators
took the lid off their evolution. The Scythian cynodonts were able
to evolve into wolf-sized predators. These cynodonts were the
protomammals closest to the heart of Harvard's Al Romer be-
cause they included the direct ancestors of all true mammals, from
platypuses and 'possums to monkeys, apes, and ourselves.
The other group that took advantage of the Tartarian extinc-
tions to expand their roles during the Scythian were the Archo-
sauria, the group that would evolve crocodiles, pterodactyls, and
dinosaurs. The earliest archosaurs of the Scythian Epoch were those
big predators the "crimson crocodiles" (Family Erythrosuchidae),
named after the red stain on the bones of the first specimens dis-
covered. All through the Triassic, from the Scythian till the close
of the Period, a titanic ecological battle was waged between the
advanced protomammals, led by the dicynodonts and cynodonts
and the Erythrosuchidae and their descendants. On the outcome
of this conflict balanced this history of the Mesozoic Era. Had the
protomammals won, they and their descendants would have dom-
inated the ecosystem during the Jurassic and the Cretaceous. If the
> crimson crocodiles and their descendants won, a totally new evo-
lutionary line would gain control.
If the clash of mighty empires is your favorite historical fare,
the Triassic is irresistible. Two mighty evolutionary dynasties col-
lided in direct competition: the advanced protomammals against
the early Archosauria. At first, the protomammals appeared to re-
capture most of their lost glory. The two-tuskers regained their
dominant position as the big herbivore. And they evolved very
advanced limb muscles, arranged nearly exactly like those of prim-
itive mammals. Mammal loyalists can be proud of these Triassic
416 I DYNASTIC FRAILTY AND THE PULSES OF ANIMAL HISTORY
Archosaurs displaced the protomammal dynasties. As the Triassic wore on,
more and more archosaur families—shown here in black—invaded the
ecological roles of large predator. By Late Triassic times, all the large
predator roles were taken over and the archosaurs had begun to invade the
herbivore guilds. And finally, in Early Jurassic times, the dinosaurs secured
complete control of both plant-eater and meat-eater components of the land
vertebrate system.
A
two-tuskers because they demonstrate how mammalian design can
win great ecological success. They can be even prouder of the cy-
nodonts, for these animals ascended the evolutionary Scala Na-
turae even more rapidly. Unlike the rather tubby two-tuskers, the
predatory cynodonts evolved sleek profiles, elongated bodies, and
slender limbs designed for rapid movement. They also produced
the most advanced, most mammal-like faces, teeth, and jaws. When
a Triassic cynodont snarled, it bared teeth that strongly resembled
a wolf's—the large canines were located far forward in the doglike
snout, the mouth front was lined with short nipping teeth (inci-
sors), and behind the canines ran a long row of teeth with multiple
cusps for slicing and chewing. The muscles of their jaws were bio-
mechanical marvels. The two muscles involved pulled across each
other, an arrangement allowing the cynodonts to bite hard with-
out placing excessive strain on the joint of the jaw bones. We hu-
mans today enjoy the advantages of such a jaw joint inherited from
our cynodont ancestors of the Triassic. Our outer jaw muscles (the
masseters) pull upward and forward while our upper set of mus-
Robert T Bakker Page 42