The Hunters of Pangaea Pangaea. Circa 145 million years before present.

Eighty million years before Purga was born, an ornitholestes stalked through the dense Jurassic forest, hunting diplodocus.

This ornith was an active, carnivorous dinosaur. She was about the height of an adult human, but her lithe body was less than half the weight. She had powerful hind legs, a long, balancing tail, and sharp conical teeth. She was coated in brown, downy feathers, a useful camouflage in the forest fringes where her kind had evolved as hunters of carrion and eggs. She was like a large, sparsely feathered bird.

But her forehead might almost have been human, with a high skullcap that sat incongruously over a sharp, almost crocodilian face. Around her waist was a belt and a coiled whip. In her long, grasping hands she carried a tool, a kind of spear.

And she had a name. It would have translated as something like Listener- for, although she was yet young, it had already become clear that her hearing was exceptional.

Listener was a dinosaur: a big-brained dinosaur who made tools and who had a name.

For all their destructiveness, the great herds of duckbills and armored dinosaurs of Purga's day were but a memory of the giants of the past. In the Jurassic era had walked the greatest land animals that had ever lived. And they had been stalked by hunters with poison-tipped spears.

Listener and her mate slid silently through the green shade of the forest fringe, moving with an unspoken coordination that made them look like two halves of a single creature. For generations, reaching back to the red-tinged mindlessness of their ancestors, this species of carnivore had hunted in mating pairs, and so they did now.

The forest of this age was dominated by tall araucaria and ginkgoes. In the open spaces there was a ground cover of ground ferns, saplings, and pineapple-shrub cycadeoids. But there were no flowering plants. This was a rather drab, unfinished-looking world, a world of gray-green and brown, a world without color, through which the hunters stalked.

Listener was first to hear the approach of the diplo herd. She felt it as a gentle thrumming in her bones. She immediately dropped to the ground, scraping away ferns and conifer needles, and pressed her head against the compacted soil.

The noise was a deep rumble, like a remote earthquake. These were the deepest voices of the diplos- what Listener thought of as belly-voices, a low-frequency contact rumble that could carry for kilometers. The diplo herd must have abandoned the grove where it had spent the chill night, those long hours of truce when hunters and hunted alike slid into dreamless immobility. It was when the diplos moved that you had a chance to harass the herd, perhaps to pick off a vulnerable youngster or invalid.

Listener's mate was called Stego, for he was stubborn, as hard to deflect from his course as a mighty- but notoriously tiny-brained- stegosaur. He asked, They are moving? They are moving?

Yes, she replied. she replied. They are moving. They are moving.

Hunting carnivores were accustomed to working silently. So their language was a composite of soft clicks, hand signals, and a ducking body posture- no facial expressions, for the faces of these orniths were as rigid as any dinosaur's.

As they approached the herd, the noise of the great animals' belly-voices became obvious. It made the very ground shake: The languid fronds of ferns vibrated, and dust danced up, as if in anticipation. And soon the orniths could hear the footfalls of the mighty animals, tremendous, remote impacts that sounded like boulders tumbling down a hillside.

The orniths reached the very edge of the forest. And there, before them, was the herd.

When diplodocus walked, it was as if the landscape were shifting, as if the hills had been uprooted and were moving liquidly over the land. A human observer might have found it difficult to comprehend what she saw. The scale scale was wrong: Surely these great sliding masses must be something geological, not animal. was wrong: Surely these great sliding masses must be something geological, not animal.

The largest of this forty-strong herd was an immense cow, a diplo matriarch who had been the center of this herd for over a century. She was fully thirty meters long, five meters tall at the hips, and she weighed twenty tons- but then even the youngsters of the herd, some as young as ten years old, were more massive than the largest African elephant. The matriarch walked with her immense neck and tail held almost horizontal, running parallel to the ground for tens of meters. The weight of her immense gut was supported by her mighty hips and broad, elephantine legs. Thick ropelike ligaments ran up her neck, over her back, and along her tail, all supported in canals along the top of her backbone. The weight of her neck and tail tensed the ligaments over her neck, thereby balancing the weight of her torso. Thus she was constructed like a biological suspension bridge.

The matriarch's head looked almost absurdly small, as if it belonged to another animal entirely. Nevertheless this was the conduit through which all her food had to pass. She fed constantly; her powerful jaws were capable of taking bites out of tree trunks, huge muscles flowing as the low-quality food was briskly processed. She even cropped in her sleep. In a world as lush as this late Jurassic, finding food wasn't a problem.

Such a large animal could move only with a chthonic slowness. But the matriarch had nothing to fear. She was protected by her immense size, and by a row of toothlike spines and crude armor plates on her back. She did not need to be smart, agile, to have fast reactions; her small brain was mostly devoted to the biomechanics of her immense body, to balance, posture, and movement. For all her bulk the matriarch was oddly graceful. She was a twenty-ton ballerina.

As the herd progressed the herbivores snorted and growled, lowing irritably where one mighty body impeded another. Under this was the grinding, mechanical noise of the diplos' stomachs. Rocks rumbled and ground continually within those mighty gizzards to help with the shredding of material, making a diplo's gut a highly efficient processor of variable, low-quality fodder that was barely chewed by the small head and muscleless cheeks. It sounded like heavy machinery at work.

Surrounding this immense parade were the great herbivores' camp followers. Insects hovered around the diplos themselves and their immense piles of waste. Through their swarms dove a variety of small, insectivorous pterosaurs. Some of the pterosaurs rode on the diplos' huge uncaring backs. There was even a pair of ungainly protobirds, flapping like chickens, running around the feet of the diplos, snapping enthusiastically at grubs, ticks, and beetles. And then there were the carnivorous dinosaurs, who hunted the hunters in turn. Listener spotted a gaggle of juvenile coelurosaurs, gamely stalking their prey among the tree-trunk legs of the herbivores, at every moment risking death from a carelessly placed footfall or tail twitch.

It was a vast, mobile community, a city that marched endlessly through the world forest. And it was a community of which Listener was part- where she had spent all her life, which she would follow until she died.

Now the diplo matriarch came to a grove of ginkgoes, quite tall, ripe with green growth. She raised her head on its cable neck for a closer inspection. Then she dipped her head into the leaves and began to browse, tearing at the leaves with her stubby teeth. The other adults joined her. The animals began simply to barge down the trees, snapping trunks and even ripping roots out of the ground. Soon the grove was flattened; it would take decades for the ginkgoes to recover from this brief visit. Thus the diplos shaped the landscape. They left behind a great scribble of openness, a corridor of green savannah in a world otherwise dominated by forest, for the herd so ravaged the vegetation of any area that it had to keep moving, like a rampaging army.

These were not the mightiest herbivores- that honor went to the giant, tree-cropping brachiosaurs, who could grow as massive as seventy tons- but the brachiosaurs were solitary, or moved in small groups. The diplo herds, sometimes a hundred strong, had shaped the land as no animal had before or since.

This loose herd had been together- traveling forever east, its members changing, its structure continual- for ten thousand years. ten thousand years. But there was room for such titanic journeys. But there was room for such titanic journeys.

Jurassic Earth was dominated by a single immense continent: Pangaea, Pangaea, which meant "the land of all Earth." It was a mighty land. South America and Africa had docked to form a part of the mighty rock platform, and a titanic river drained the heart of the supercontinent- a river of which the Amazon and Congo were both mere tributaries. which meant "the land of all Earth." It was a mighty land. South America and Africa had docked to form a part of the mighty rock platform, and a titanic river drained the heart of the supercontinent- a river of which the Amazon and Congo were both mere tributaries.

As the continents had coalesced there had been a great pulse of death. The removal of barriers of mountain and ocean had forced species of plants and animals to mix. Now a uniformity of flora and fauna sprawled across all of Pangaea, from ocean to ocean, pole to pole- a uniformity sustained even though vast tectonic forces were already laboring to shatter the immense landmass. Only a handful of animal species had survived the great joining: insects, amphibians, reptiles- and protomammals, reptilian creatures with mammalian features, a lumpen, ugly, unfinished lot. But that handful of species would ultimately give rise to all the mammals- including humans- and to the great lineages of birds, crocodiles, and dinosaurs.

As if in response to the vast landscape in which they found themselves, the diplos had grown huge. Certainly their immensity was suitable for these times of unpredictable, mixed vegetation. With her long neck a diplo could work methodically across a wide area without even needing to move, taking whatever ground cover was available, even the lower branches of trees.

In the clever orniths, though, the diplos faced a new peril, a danger for which evolution had not prepared them. Nevertheless, after more than a century of life, the matriarch had absorbed a certain deep wisdom, and her eyes, deep red with age, betrayed an understanding of the nimble horrors that pursued her kind.

Now the patient orniths had their best opportunity.

The diplos still crowded around the wrecked ginkgo grove, their great bodies in a starburst formation. Their heads on their long necks dipped over the scattered foliage like cherry picker mechanical claws. Youngsters clustered close, but for now they were excluded by the giant adults.

Excluded, forgotten, exposed.

Stego ducked his head toward one of the diplo young. She was a little smaller than the rest- no larger than the largest African elephant, a genuine runt. She was having trouble forcing her way into the feeding pack, and she snapped and prowled at the edge of the formation with a massive birdlike twitchiness.

There was no real loyalty among the diplos. The herd was a thing of convenience, not a family grouping. Diplos laid their eggs at the edge of the forest, and then abandoned them. The surviving hatchlings would use the cover of the forest until they had grown sufficiently massive to take to the open land and seek a herd.

The herds made strategic sense: Diplos helped protect each other by their presence together. And any herd needed new blood for its own replenishment. But if a predator took one of the young, so be it. In the endless Pangaean forests, there was always another who would take her place. It was as if the herd accepted such losses as a toll to be paid for its continuing passage through the ancient groves.

Today it looked as if this runty female would pay that toll.

Listener and Stego took their whips of diplo leather from around their waists. Whips raised, spears ready, they crept through the rough scrub of saplings and ferns that crowded the edge of the forest. Even if the diplos spotted them they would probably not react; the diplos' evolutionary programming contained no alarm signals for the approach of two such diminutive predators.

A silent conversation passed in subtle movements, nods, eye contacts.

That one, said Stego. said Stego.

Yes. Weak. Young.

I will run at the herd. I will use the whip. Try to spook them. Separate the runt.

Agreed. I will make the first run...

It should have been routine. But as the orniths approached, coelurosaurs scuttled away and pterosaurs flapped awkwardly into the air.

Stego hissed. Listener turned.

And looked into the eyes of another ornith.

There were three of them, Listener saw. They were a little larger than Listener and Stego. They were handsome animals, each with a distinctive crest of spiny decorative scales running down the back of its head and neck; Listener felt her own spines rise up in response, her body obeying an unbidden, ancient instinct.

But these orniths were naked. They had no belts of woven bark around their waists like Listener's; they carried no whips, no spears; their long hands were empty. They did not belong to Listener's hunting nation, but were her remote cousins- wild orniths- the small-brained stock from which her kind had arisen.

She hissed, her mouth gaping wide, and strode into the open. Get away! Get out of here! Get away! Get out of here!

The wild orniths stood their ground. They glared back at Listener, their own mouths gaping, heads bobbing.

A tinge of apprehension touched Listener. Not so long ago three like these would have fled at her approach; the wild ones had long learned to fear the sting of weapons wielded by their smarter cousins. But hunger outweighed their fear. It had probably been a long time since these brutes had come across a diplo nest, their primary food source. Now these clever opportunists probably hoped to steal whatever Listener and Stego managed to win for themselves.

The world forest was getting crowded.

Listener, confronted by this unwelcome reminder of her own brutish past, knew better than to show fear. She continued to stalk steadily toward the three wild orniths, head dipping, gesturing. If you think you are going to steal If you think you are going to steal my my kill you have another think coming. Get out of here, you animals. kill you have another think coming. Get out of here, you animals. But the mindless ones replied with hisses and spits. But the mindless ones replied with hisses and spits.

The commotion was beginning to distract the diplodocus. That runty female had already ducked back into the mass of the herd, out of reach of the hunters. Now the big matriarch herself looked around, her head carried on her neck like a camera platform on a boom crane.

It was the chance the allosaurs had been waiting for.

The allos stood like statues in the forest's green shade, standing upright on their immense hind legs, their slender forearms with their three-clawed hands held beneath. This was a pack of five females, not quite fully grown but nevertheless each of them was ten meters long and weighed more than two tons. Allosaurs were not interested in runtish juveniles. They had targeted a fat male diplo, like themselves just a little short of full maturity. As the herd milled, distracted by the commotion of the squabbling orniths, that fat male got himself separated from the protective bulk of the herd.

The five allos attacked immediately, on the ground, in the air. With hind claws like grappling hooks they immediately inflicted deep, ugly wounds. They used their strongly constructed heads like clubs, battering the diplo, and teeth like serrated daggers gouged at the diplo's flesh. Unlike tyrannosaurs they had big hands and long, strong arms they used to grab on to the diplo while dismembering him.

Allosaurs were the heaviest land carnivores of all time. They were like upright, meat-eating, fast-running elephants. It was a scene of immense and ferocious carnage.

Meanwhile the diplo herd was fighting back. The adults, bellowing in protest, swung their huge necks back and forth over the ground, hoping to sweep aside any predator foolish enough to come close. One of them even reared up on her hind legs, a vast, overpowering sight.

And they deployed their most terrible weapon. Diplo tails lashed, all around the herd, and the air was filled with the crackle of shock waves, stunningly loud. A hundred and forty-five million years before humans, the diplos had been the first animals on Earth to break the sound barrier.

The allosaurs retreated quickly. Nevertheless one of them was caught by the tip of a supersonic whip-tail that crashed into her ribs. Allosaurs were built for speed and their bones were light; the tail cracked three ribs, which would trouble the allosaur for months to come.

But the attack, in those few blistering moments, had been successful.

Already one great leg had collapsed under the male diplo, its ripped tendons leaving it unable to sustain its share of the animal's weight. Soon his loss of blood would weaken him further. He raised his head and honked mournfully. It would take hours yet for him to die- the allosaurs, like many carnivores, liked to play- but his life was already over.

Gradually the crackle of whiplash tails ceased, and the herd grew calmer.

But it was the big matriarch who delivered the last whiplash of all.

When the allosaurs had attacked, the orniths, suddenly united in terror, had fled the clearing. Now Listener and Stego skulked side by side in the forest-edge scrub, their unused weapons in their hands, their hunt thwarted. But it wasn't all bad news. When the allos were done feeding there might be meat to be scavenged from the fallen diplo.

Then came that last whiplash. The huge diplo's tail landed clean across Stego's back, laying his skin open to the bone. He screamed and fell, tumbling out into the open, his mouth agape. The slit pupils in his eyes pulsed as he gazed up at Listener.

And one of the allosaurs, not far away, turned with glassy interest. Listener stood stock still, shocked.

With a single bound the allo reached Stego. Stego screamed and scrabbled at the mud. The allo poked him curiously, almost gently, with her muzzle.

Then, with astonishing speed, the allo's head shot forward and delivered a single clean bite, all but severing Stego's neck. She grabbed him by the shoulder, lifting him high. His head dangled by a few threads of skin, but his body twitched still. She carried him to the edge of the forest, away from the herd, where she began to feed. The process was efficient. The allo had joints within her jaw and skull, so that like a python she could open her mouth wide and position her teeth, the better to consume her prey.

Listener found herself staring stupidly at an allosaur track, a three-toed crater firmly planted in the trampled mud. A hunter without her mate is like a herd without its matriarch A hunter without her mate is like a herd without its matriarch: The ornith proverb sounded in her head, over and over.

The big matriarch diplo swung her head around to stare directly at Listener. Listener understood. The orniths' antics had given the allos their chance to attack. So, with her whiplash, the matriarch had exposed Stego. She had given him to the allos. It had been revenge.

The matriarch turned away, lowing, as if contented.

Something hardened, a dark core, in Listener's mind.

She knew she would spend the rest of her life with this herd. And she knew that the matriarch was its most important individual; providing protection to the rest with her sheer bulk, leading them with her wisdom acquired over long years. Without her the herd would be much less well coordinated, much more under threat. In a way, this matriarch was the most important individual creature in Listener's life.

In that moment, she swore vengeance of her own.

Each night the orniths retreated to their ancestral forest, where once they had hunted mammals, insects, and the nests of diplodocus. They scattered in little pockets, and surrounded the area with heavily armed sentries. That evening, the mourning was extensive. This ornith nation was only a few hundred strong, and could ill afford to lose a strong, intelligent young male like Stego.

Even as the cold of night drew in, Listener found it hard to rest.

She gazed up at a sky across which auroras flapped, steep three-dimensional sculptures of light, green and purple. In this age Earth's magnetic field was three times the strength it would be in the human era, and, as it trapped the wind streaming from the sun, the shining auroras would sometimes blanket the planet from pole to pole. But the lights in the sky meant nothing to Listener, and brought no comfort or distraction.

She sought refuge in memories of happier, simpler times when she and Stego, emulating their distant ancestors, had hunted for diplo eggs. The trick was to seek out a patch of forest floor, not too far from the edge, that looked apparently lifeless, strewn with leaves and dirt. If you put your sensitive ear to the ground you could hear, if you were lucky, the telltale scratching of diplo chicks in their eggs. Listener had always preferred to wait, to guard "her" nest from others, until the diplo chicks began to break out of their eggs and stick their tiny heads out of the scattered dirt.

For an inventive mind like Listener's, there was no end to the games you could play.

You could try to guess which chick would come up next. You could see how quickly you could kill a new emergent, snuffing it out within a heartbeat of its first glimpse of daylight. You could even let the chicks come out of their shells altogether. Already a meter long, with their flimsy tails and necks dangling, the chicks' only priority was to escape to the deeper forest. You could let a chick get all the way to a patch of scrub- almost- and then haul it back. You could nip off its legs one by one, or bits of its tail, and, crunching the little morsels, see how it still struggled, as long as its brief life lasted, to get away.

All smart carnivores played. It was a way of learning about the world, of how prey animals behaved, of honing reflexes. For their time, orniths had been very smart carnivores indeed.

Once, not more than twenty thousand years ago, a new game had occurred to one of them. She had picked up a handy stick in her grasping hand, and she used that to probe for unbroken eggs.

By the next generation the sticks had become hooks to drag out the embryos, and sharpened spears to stab them.

And by the next, the new weapons were being trialed on bigger game: juvenile diplos, younger than five or six years, not yet part of a herd but already a meat haul worth hundreds of embryonic chicks. Meanwhile a rudimentary language was born, of the subtle communications of pack hunters.

A kind of arms race followed. In this age of immense prey, the orniths' better tools, more sophisticated communication, and complex structures were quickly rewarded by bigger and better hauls of meat. Ornith brains rapidly expanded, the better to make the tools, and sustain societies, and process language- but there was a need for more meat to feed the big expensive brains, requiring better tools yet. It was a virtuous spiral that would operate again, much later in Earth's long history.

The orniths had spread all over Pangaea, following their prey herds as they crisscrossed the supercontinent along their vast ancestral corridors of parkway.

But now conditions were changing. Pangaea was breaking up, its backbone weakening. Rift valleys, immense troughs littered with ash and lava, were starting to open. New oceans would be born in a great cross shape: Eventually the Atlantic would separate the Americas from Africa and Eurasia, while the mighty equatorial Tethys would separate Europe and Asia from Africa, India, Australasia. Thus Pangaea would be quartered.

It was a time of rapid and dramatic climate change. The drift of continental fragments created new mountains which, in turn, cast rain shadows across the lands; the forests died back, and immense dune fields spread. Generation by generation- as their range disintegrated, and the vegetation no longer had time to recover from their devastating passage- the great sauropod herds were diminishing.

Still, if not for the orniths, the sauropods might have lingered much longer, even surviving into the great high summer of dinosaur evolution, the Cretaceous.

If not for the orniths.

Though Listener went on to take more mates and to raise proud clutches of healthy and savage young, she never forgot what had become of her first mate, Stego. Listener did not dare challenge the matriarch. Everyone knew that the best chance of the herd's survival was for the powerful old female to continue her long life; after all, no new matriarch had emerged to replace her.

But, slowly and surely, she drew up her plans.

It took her a decade. Over that time the numbers of diplos in the herd halved. The allosaurs too went into steep decline across the supercontinent as their prey animals became scarce.

At last, after a particularly harsh and dry season, the old one was observed to limp. Perhaps there was arthritis in her hips, as there evidently was in her long neck and tail.