Friday, November 14, 2014

Prehistoric Warfare Episode 3: Allosaurus vs Stegosaurus



Now for something different. In 2004, Animal Planet showed as new series called Animal Face Off, a series reconstructing conflicts between coexisting animals. While the execution was clumsy and lacking, the concept is strong and I think easily applied to prehistoric fauna.  Ideally, there would be professionals discussing the situations, but unfortunately, you have only me. First I will compare the animals, and then depict their behavior, before concluding with the final battle.  The outcome will be my personal opinion; and there would be many times when the outcome would be decidedly different. This is not a scientific consensus, but one researcher’s opinion.

We all love dinosaur battles. They’re always a high point in a film. It’s childish, but it’s just plain fun. So, I’m hoping to use this opportunity to use this almost-universal appeal to get people thinking and talking about ecology, biomechanics, and behavior. Only one or two of these stories will be based on actual fossils-the rest are likely possibilities that must have happened sometime or another. In real life, animals usually don’t fight on even terms, but it does happen. Sometimes prey turn the tables, sometimes predators quarrel between themselves, but it can happen. I hope you enjoy this. Again, first I will have two scenes, one for each animal showing them in their habitat and showcasing their particular skills, then finally concluding with a battle between the two.


I MUST WARN THAT  THIS WILL BE VIOLENT. IF YOU HAVE A PARTICULARLY VIVID IMAGINATION, OR HAVE AN AVERSION TO GRAPHIC NATURALISTIC VIOLENCE, I STRONGLY SUGGEST NOT CLICKING ON THE CUT




The last time on this feature, we saw the emergence of a new, large predator and its reign over the American West.  It’s been 37 million years since then, and that’s a long time in terms of even evolution. To put it this way, 37 million years ago, elephants were the size of ponies, horses the size of Labradors, and our ancestors were similar to langurs or colobus monkeys.  In this time, an evolutionary arms race has continued and intensified. Dilophosaurus was made obsolete by bigger, stronger, more intelligence predators. Sarahsaurus has been dwarfed by its successors, who grow in response to bigger, better defended plants and the aforementioned predators.  Dinosaurs have become spectacular.

This is the Morrison formation, 155 million years ago. It’s warm and seasonal , as before, but the similarities end there. Lakes have given way to vast rivers and a sea in Alberta intruding from the north, huge evergreen forests with 60-foot trees come and go, and between the rivers are great plains. This is before grass, so the main plains plants are cycads and ferns, with rushes and horsetails along the riverbanks. 

Right now, it’s the beginning of the wet season in what is today Colorado, on a flat plain where the Rockies will rise. Great rivers flow through it, and the recent rains is making them swell again. With the rains come the greenery, and that brings the herds.  Already a herd of Diplodocus is here, their long necks allowing them to both rake the leaves off the giant pines or practically vacuum cycad and fern fronds.  The secondary forest has already suffered greatly from the herds, but it still stands strong, allowing for other forests to regenerate from previous defoliation. 

The diplodocus hooting is joined by another, different bellow.  Another sauropod herd, this one of Camarasaurs, has joined to feed on the new growth. They are followed by swarms of ornithopods-ranging from the large, advanced Camptosaurus to the medium-sized racer Dryosaurus, to the tiny Othnielosaurus. They feed on both the plain and the forest, and as the Camarasaurs continue their slow and stately march, the ornithopods spread out to feed. Only a few will follow the Camarasaurs to their destination to feed on whatever scraps fall from their chomping jaws. 

The next day, another, smaller herd arrives. It’s a mixed group of Barosaurus and Brachiosaurus, two very different, very rare sauropods. In Portugal, Dinheirosaurus and Lusotitan form similar groups, and  in Tanzania their sister species Torneria and Giraffatitan act the same way. The heavy-necked Barosaurs don’t have the same flexibility in their neck as their relatives Apatosaurus and Diplodocus, so unless they rear on their hind legs, they typically browse lower growth. Meanwhile, Brachiosaurus can stretch their necks 35 feet over the ground to chop up the highest leaves. 

Later that week, a herd of Stegosaurs join the feast. They are low-browsers, eating younger trees  by the edges of the forest or  grazing in the plains between the forest and the river. They’re ready to mate, judging by the pink flushes on their maroon plates.  High-plated bulls and long-legged cows flash their plates, in a visual equivalent of a bird chorus.

The forest thins in some places-sometimes it’s the younger sections outgrowing from the main group, or the older groves that have barely survived the relentless munching. This is ideal for the Camptosaurus and Stegosaurus as they can rear up to eat the saplings or simply plod along cropping the cycads and ferns.


It’s also more dangerous.  The denser forest is too dense for large predators to hide, and the plains provide no cover, so this medium growth allows for ideal stalking cover.  The most successful predator of the past 5 million years will exist for another 5, and continue a worldwide legacy.  This is Allosaurus. Specifically, a 30-foot female at the beginning of maturity. She’s had enough experience to know how to hunt large prey, but is still agile and energetic. Allosaur minds are demanding-they’re not quite bright enough to play, but they still require stimulation. If she can kill a large prey, she might attract a mate. Likewise, she can simply wait for the smell of carrion, which can mean a male is hunting nearby. Either way, she puts her nose in the air. The mixed scents of the forest reveal many small animals, but they would be only prey for Ornitholestes or its more primitive cousin Coelurus. She’s eaten them in turn, but they’re hard to catch and they’re only a mouthful. 

More promising scents waft over. Sauropods…she’s killed some youngsters before, but has had enough times where the adults chased her off. Right now she can’t smell any subadults that aren’t mixed in with the adults. They might segregate as more herds join in, but it doesn’t look like she can pick off any today.

The wind shifts, and so does she. She’s spooked prey on accident when the wind changes, so when she can’t smell them anymore she walks around until she can again. This time she smells much nearer prey. Stegosaurus-they have younglings too, but they’re dangerous. Sometimes adults can be taken late in the season when illnesses begin to take their toll and when Allosaurs hunt in mated pairs. 
She pivots her head to peer towards the direction of the scent. Stereoscopic vision is not found on large theropods as of yet-instead they have large obstructing horns and crests above or behind their eyes to attract mates.  Her horns are soft blue-those of a male would be bright red.   She can make out the familiar colors of her prey. The brown-green bodies tipped with maroon, red, and pink are the Stegosaurs, but among them are the black forms of Camptosaurus, with bright red markings on their heads and tails and white stripes on their backs. 

Camptosaurus are interesting prey-they’re common due to their very efficient teeth and jaws allowing them to eat more and faster. They’re fast-not as fast as smaller dinosaurs but as fast as any adult Allosaur. They have no weapons against larger predators other than their speed and maneuverability, but it’s enough. More problematically for Allosaurus, they tend to herd with Stegosaurus, which are much slower but very well defended. She’s seen other Allosaurs with large, infected puncture wounds-she doesn’t know how the wounds were delivered, but the large tail spines speak for themselves. She’s been lucky-all of her scars are from falls or from fighting other predators.
She’s hungry, but she’s patient. She’s going to wait for an opportunity to present itself. As long as the wind doesn’t shift again, she will stand there behind the cover of trees to peer at the herd. A hyperactive mammal mind would get bored, while a primitive crocodile mind would simply stay at the spot for days. She can wait a few hours, but hopefully she won’t have to.

Her luck kicks in-she sees movement. A Camptosaur cockerel has wandered off from his harem of pullets to browse on new greens. His jaws made short work of the spiny, tough cycad leaves and he peeks in to get at the juicy seeds. His beak slices through the leaves and cracks the husk to get at the soft fiber underneath full of oil and sugar. 

Cycads have been fighting a battle against herbivores-they’ve grown tough bark to deter Permian herbivores, grown higher to foil dicynodont tusks and beaks, and armored their seeds against sauropods and their ancestors. However, a combination of dinosaur size and an increasingly more powerful beak have rendered their defenses obsolete. Poison and sharp fronds will develop in turn, but armored heads and necks and more sophisticated stomachs will defuse those in turn. 
Camptosaurus is equipped to deal with this era’s cycads, but the tall thick fronds hamper his vision even with his strong short forelimbs shove them aside and his wide set eyes give a very wide scope.  This is the moment Allosaurus has been waiting for, and she makes her move. 

Allosaurus are not that stealthy, and she crashes through the growth in her charge. The noise alerts the herd, and most of them pause and look away from their food. Her foot splinters fallen branches, and that gets the skittish Dryosaurs racing away. The Camptosaurs scatter. The Stegosaurus fan out.
It’s too late for the target bull, however. He’s fast enough to have avoided many allosaur and ceratosaur attacks in his lifetime, but his moment of distraction has caught him off-guard. He has to rear up to push away the fronds of the cycads, and only then does he see and smell his attacker. His mind switches from feeding to alarm to flight and he turns to run.  He’s got good acceleration in open country and has outpaced many allosaurs with his stamina, but he first needs to clear the foliage.
No sooner than he breaks into the clear than Allosaurus is on him. She’s got the running start, and while her stamina is limited compared to Camptosaurs, it’s enough to get the job done.  It’s then when his luck runs out.  During this whole affray, a smaller armored dinosaur has been grazing nearby. He’s a Gargoyleosaurus, the first in a long line that will succeed the Stegosaurs and foil the Allosaurs. He’s only the size of a pygmy hippo, but his head and body are armored with bone plates and spines. He’s even slower than Stegosaurus and has no weapon to counterattack, but he’s too small and heavily armored for any predator to consider him with the tackle. At worst they break their teeth and scar their faces. At best they only have enough food for a day.  While meatier than Dryosaurus, ankylosaurs are even less worth it. 

Right now, though, Gargoyelosaurus is about to help out Allosaurus. The panicked Camptosaurus doesn’t pay attention where he’s running, and he crashes past a cycad and right into Gargoyelosaurus. Both tumble. Gargoyleosaurus rolls over, but is light enough to keep rolling until he lands feet first rather than landing on his back and becoming entirely helpless. Camptosaurus flips over, crushing ferns as he goes. He’s on his feet, but it’s too late.
Disoriented, rears up and swings his head around to see where the predator is.  From a stooping run, Allosaurus opens her mouth as she runs in alongside.

Allosaurus’ skull is light but sturdy. It’s like a box made of metal pipes making up the lines and cardboard between them. Against other allosaurs, she rams them with her horns. Against prey, she goes in for the kill with her open mouth.  Her mouth gapes wide open to expose her broad, curved, serrated teeth. They’re not as sturdy as a Tyrannosaurus’ teeth-they’re not bone-crunching. Instead, they are like a saber-at high speed they slash at prey with the sharp blade and long cutting surface, slicing through skin and muscle.  Her head is light enough not to slow her down as she charges, allowing her to catch up with her prey, but sturdy enough to withstand the violent collision.  As she hits, she opens her arms so that her strong, curved talons can pierce into the prey. Her left claw hooks into the side of Camptosaurus as her teeth shred the flesh behind his shoulder.  In a second he’s down again.

He slams down on his side in shock from the combination of the blood loss and her powerful swipe. Allosaurus nearly skids past him, slipping on his blood, but she manages to stop with a powerful stroke of her foot. They’re parallel to each other. Camptosaurus looks up to the left to see his assailant, his legs and tail flailing in panic and pain.  Their eyes meet-his bulging in terror and confusion, hers dilated in as adrenaline propels her killing.  Now she bites into his neck. Her bite is relatively weak compared to later predators, but she’s not breaking his neck, but cutting it up. Arteries, veins, and windpipe are severed as she closes her sawing teeth on him and gives it a short, strong shake with her powerful neck.  Terror and agony end for Camptosaurus.

There’s many other Allosaurs in the area as the herds migrate to these lush pastures, and the riverside has its own dangerous predators, so she eats fast before the scent can reach her rivals. With powerful tugs of her neck and slashing bites of her jaws she carves him into chunks, her talons manipulating the 2- ton corpse so to eat more efficiently. She is the apex predator of the Jurassic-no other is as powerful, versatile or efficient.   She will mate soon and bear many children before she passes from food poisoning from rotten meat. 

As the Allosaurus feeds, a herd of Stegosaurs makes their way to the river. Their huge size means spreading out into small groups or individuals to find food, and it takes a lot of foliage to power five tons of muscle. The lush horsetail forests by the rivers provide a banquet, and they eagerly tuck into the short plants. Longer shoots are shoved over by their shoulders and elbows to bring them down to mouth level.  The crocodiles resting nearby shuffle into the water, no match for the giant herbivores and reluctant to become trampled.

 Crocodiles, however, are not the only predators here. There are two theropods here. Allosaurus rules the plains, but the lowlands and rivers belong to two different, specialized theropods.  One is the rare giant Torvosaurus and the more common but still second-rate Ceratosaurus.  Ceratosaurus are smaller, lighter predators, but still dangerous. Their maxillary teeth (the top row) are bigger than Allosaurus’ and the Ceratosaurus aren’t picky.  They lurk in tall horsetails and rushes for dinosaurs to go towards the water. If they’re really hungry, they will snack on the crocodiles and fish, pursuing them into the water. Allosaurus don’t hunt near the river in the wet season-the lighter Ceratosaurus are more maneuverable and run circles around them, and in the flooded rivers the smaller theropod can turn the tables. 

They also hunt in pairs. Sometimes it’s a parent and their offspring, but most often they’re mates. Right now, one mated pair is watching the river. A Camarasaur carcass once washed downstream to their beach once and provided them with food for weeks.  Last week they caught not only an unwary dryosaur that tripped in the mud but also a wounded Allosaur that had been mauled by a rival. They’re not smart enough to be picky and dangerous enough to afford that kind of generalization.
The Stegosaurs provide an interesting challenge. They’ve tasted Stegosaur before. The male once scavenged a carcass with his previous mate, and the female once was lucky enough to kill a juvenile. They know their food, and Stegosaurus are food. Cooperative hunting has just evolved-the most sophisticated they can get is to flank the prey as they attack. The duo won’t last too long-they mated just a week ago and soon they’ll depart to find other mates, chowing on fish in the meantime.
Right now, they intend to eat something big.  Two Stegosaurus bulls are rubbing shoulders eating the same clump of horsetails, and quickly antagonizing each other in their hormonal stage. They flash their plates at each other,  shouldering each other with their powerful upper arms. They neck wrestle, hormones finally kicking into gear.  The rest of the herd spreads out, avoiding the fracas. This is the opening the Ceratosaurs have hoped for.

One of the Stegosaurs, a gigantic cow, is the outermost.  An ideal prey would be her calf, but said calf is on the far side and dangerously close to two more adult stegosaurs.  Usually they wouldn’t do this. Usually they’d be patient. But this time their patience has run out.  More sophisticated theropods like birds can wait it out, like the birds perched nearby the scene.  Ceratosaurus, however, is an older design, one evolved for overpowering prey. It’s in this unique habitat and hunting style that Ceratosaurus is still competitive. They won’t dare venture too far in an Allosaur territory alone, or tackle a Stegosaur alone, but they see each other and smell each other, and that gives them courage.
The Ceratosaurus charge in-they have no strategy as it hasn’t been evolved yet. The killing tactic is brutal, bloody, and simple-charge in and use their open mouths like machetes. The stegosaur barely has time to react when the Ceratosaurs hit.  Fortunately for her, she doesn’t have to.  The broad, razor-sharp teeth slash at her hide, but it’s not a killing blow.  Her sides are peppered with tubercles and small bumpy scales, evolved to deal with flesh-rending teeth like those of Ceratosaurus. She’s in pain, though, and she lets out a loud bellow that alerts the rest of the stegosaurs.

They scatter as she pushes off with her right feet, turning 90 degrees and swinging her powerful tail. One ceratosaur, a red-horned male gets slammed by her 5-ton body and send tumbling into the river. The black-horned female scrambles backwards, nimbly avoiding the deadly tail not once but twice.  She roars and snaps her jaws in frustration.  The Stegosaurus walks to firmer ground where she can move easier and take away the Ceratosaurs’ advantage, but that allows for the male predator to right himself. 

The Stegosaurus moves inland, trying to keep her attackers on the same side, but they manage to flank her, even by accident.  She swings her tail-the deadly spines miss, but the muscular tail swats both of them and force them back.  

The physique of Stegosaurus is remarkable. The short forelimbs give her a low center of mass based on the thorax, not the hips. The femurs and humeri are much longer than the other limb bones, making the hips and shoulders the pivot point. This makes her able to quickly turn her forequarters or hindquarters or even both.   The tail bones are almost all the same size, supporting long powerful tail muscles and giving it a lot of flexibility. The spines on the vertebra closer to the pelvis are very tall for huge muscle attachments and augmented with prominent transverse processes to attach more muscle, giving the tail even more power. 

She digs in her forelimbs and strides sideways with her hindlimbs, then curls her tail inwards and then back out to swipe again. Both Ceratosaurus jump back again, their agility keeping them from harm.  They step forward together, but another flick of that deadly tail drives them back again.  The standoff ensues. The Jurassic dinosaurs, however, lack the stamina of their more sophisticated successors.  The Ceratosaurus must brave the defenses and charge once more, or flee one last time.
The duo chooses the former. Both charge at the same time, hoping to use their combined strength and weight to knock down the Stegosaurus and tear her apart. She does not cooperate; Stegosaurus, having secured her hindquarters, pushes off with her front feet and swiftly changes her position in a 90 degree rotation.  The last thing the male Ceratosaur sees is the tail spines coming at the right side of his face.  One spike pieces into bone right in front of the anteorbital (gaps in the skull to make it light, in front of the eyes) fenestrae in a nonlethal but extremely painful blow,  the other bone war pick ends the pain instantly by entering the postorbital fenestrae, stabbing through the jaw muscle and into the brain case. 

An equally powerful backswing not only pulls the spines out of the male’s skull but drives the opposite set of spikes into the abdomen of its mate.  No matter what species, a penetrating stab wound to the abdomen is horrific even if it’s not fatal. In this case, it impales 3 feet deep into the intestines.  She goes into shock and falls alongside her mate. If she doesn’t bleed out, she will almost certainly die of septic infection. Most likely she will die next to her mate, food for the scavengers.
Stegosaurus doesn’t care about their fate. She is safe, her offspring is safe, and her wounds will avoid infection with a little luck. The hormones cease, her heartbeat slows, and her body goes back into its neutral position. Alarm turns to hunger, and she returns to the horsetails with the rest of her reassembling herd.  She has survived predators before, and will instead die of a stomach parasite.

A generation passes. Forests rise and fall, expand and shrink. The herds come and go, along with their predators. The descendants of Allosaurus and Stegosaurus die or grow to maturity.  Eventually, they will meet.

The precipitating circumstance is a drought. The normal rhythm of wet and dry is sometimes disrupted by the fickleness of weather.  In this case, the dry season goes for too long.  Without the rains, the forest and plain shrink and the river dries up.  The Ceratosaurs, crocodiles, and Torvosaurs are the first to move upstream, with the herds of herbivores following them as the greenery dies.  In times of abundance, the herbivores spread out and thrive, but in this lean time they form vast caravans that stretch for miles on end.

One herd is the Stegosaurs. Among them are the three surviving offspring of the Stegosaurus we met earlier-a pair of males from the same clutch and their older sister.  They each have offspring, carefully herded in the middle away from harm. Their smells are familiar to each other, and so they stick together for comfort. Friendship takes advanced cognitive functions, but they know they’re related, and their herding instinct does the rest. They cannot suckle their offspring like mammals, so all they can do for the starving infants is to stay between them and whatever predators come.
They coast on their momentum, following the smells of green and water, growing stronger and stronger. They must be a few miles away. Then the wind shifts, the scent being replaced by another menacing presence and the agonizing bellow of a herbivore.  The Stegosaurs hustle, walking as fast as their stocky bodies can allow. Some look back and discover the source of the alarm.
Behind them is a Diplodocus, half-blind and lost from her herd. She is beset by a gang of Allosaurs. Allosaurus usually only stand each other’s company during the mating season as pairs, but as their prey form herds and leave a train of the dead and dying, the predators congregate on the rich pickings, In this case, a nearby Diplodocus herd is being tailed by the Allosaurs, and the wandering senior citizen makes for a tempting target.

She stumbles about, but her moments are few. Every time she takes a swipe of her neck or tail to fend off an attacker, another rips of piece of lean flesh off her. She’d be a better find if she was well-fed, but the Allosaurs will take what they can find, and her full adult size still provides plenty of meat. Later group hunters like mobs of dromeosaurs and creodonts or sophisticated hunting parties of dogs and cats and primates will turn this harrying into an art, but even this crude feeding frenzy will do the trick.  Diplodocus manages to slash several attackers with her whip tail and even crushes one with her front feet, but her bleeding, mauled legs finally give out, and she is quickly devoured.

The Allosaurs butcher the fallen giant with great bites of their jaws, and those left out turn to their crushed comrade to devour him as well. There is still one hungry Allosaurus, though. This is eldest daughter of the Allosaurus we met, and she’s used to getting her way. There’s just too many rivals to have her fill and too much blood in the air to calm down.  She can smell the food and see the corpses, but she is left out. The scent of blood and dead sauropod mingles with a new one. Yes, it’s Stegosaurus. She’s had some. Early in the drought she scavenged an old bull and she’s found that the calves are delicious if they can be picked off safely.  They’re food.

She pivots her head-sure enough, she can make out the shapes of stegosaur juveniles, ranging to half-sized subadults to tiny infants hatched late but still strong enough to make the journey. The herd is moving slow, but has just sped up. Allosaurus isn’t as fast as she could be, either, but she can outpace a Stegosaurus even on a bad day like today. She follows her nose and makes a beeline for the herd.

The problem with a Stegosaurus herd is the twitching tails. It’s an instinct to menace predators and it kicks in when the alarm signals go off in the brain, but right now it’s making it difficult for them to keep a tight formation.  As they spread out, it gives Allosaurus her chance. Now she can slip in among them to take a juvenile. She’s done this plenty of times. She might not have the eyes of an eagle or nose of a dog, but her senses are keen and trained through years of experience and millions of years of evolutionary specialization. 

There’s a small juvenile by one of the twins. She goes for it. The chase is slowed by hunger, but desperation adds its own speed. She’s blocked off from a rear approach by the older sister Stegosaurus, but Allosaurus tries to run around the male  from the front. He’s faster than he looks, though, and blocks her path. A diving lunge of her powerful jaws misses. Frustrated, she bites onto his neck as they race. This would kill a Camptosaur. This would stop even a giant sauropod in its tracks. But it does nothing against Stegosaurus, who wrenches himself free and shoulder-checks his attacker. 

Stegosaurus has what is called a Pixane in proper armory terminology-a mailed neck guard covering throat and collar. She didn’t hit him with enough force to pierce the bones. She’s not a Tyrannosaurus-Allosaurs eat prey defended by flesh, not bone.  

 Allosaurus turns to attack another juvenile, but she’s not quick enough-the little one rises to his hind feet and runs in a short burst. Only juveniles can do this-sometimes adults can stand as tripods but their mobility is limited.  She bites nothing but dust. 

 She turns again to the brother that checked her. This time she tries to bring him to the ground-her talons sink into his shoulder and bites into a neck plate to pull him to the ground.  The thin plate bleeds profusely as she sinks her teeth into it. Allosaurus bites with all her power and pulls with her sturdy, powerful neck. He’s starting to stumble and lean to his side, struggling to keep on his feet.  Something must give way- her teeth, his plate, or his balance.

It’s the plate- there’s a sickening crunch as she bites away the plate.  It’s nothing but thin bone, and not worth gnawing, so she coughs the bone out of her mouth, frustrated.  She’s drawn blood, though, and she’s not discouraged. If she can get a lucky bite, or leap onto his side, she can kill him. It’ll take a trick, and sometimes it doesn’t work but it’s her best chance to bring him down.

Then a collision interrupts the battle. The older sister Stegosaur has through a combination of accident and protectiveness rammed into the Allosaurus. The two crash into the dust on their stomachs, as the herd moves past them. It’s not an easy picking anymore. It’s not a chase anymore. It’s a duel to the death. 

They slowly circle each other, the Allosaurus roaring in frustration, Stegosaurus bellowing back and flashing her plates as a menace.  Losing focus and in a furious combination of rage and hunger, Allosaurus lunges, aiming bites at Stegosaurus’ neck and head. Stegosaurus ducks and dodges, and when Allosaurus finally bites down, her neck armor thwarts the theropod and breaks off teeth. 

Curved into a defensive posture-perpendicular to the enemy, with head and tail both turned to face the attack, Stegosaurus walks slowly backward.  A few feints from Allosaurus fail to do anything but move the Stegosaurus back. A flanking attempt only provokes Stegosaurus to move with Allosaurus. They’re matched in maneuverability.  The rest of the herd is forgotten. It’s no longer a chase, it’s a duel. Allosaurus feints, Stegosaurus swipes.  


The standoff leads to a pause, both panting in exhaustion. Stegosaurus changes position-she turns around to walk back to the herd.  Allosaurus seizes the opportunity. Even as she opens her jaws to inflict a mortal blow to Stegosaurus’ flanks, Stegosaurus swings her deadly tail. Before Allosaurus can sink her teeth into Stegosaurus, the spikes hit. It’s not a lateral blow-she twists her powerful tail muscles to angle the spikes and the tail swipe upwards. If Allosaurus was at a different position, her thighs would be the target and she would be crippled. Instead, the weapon stabs deep into her hips. One spike pierces her pubic bone, another finds nothing but flesh and goes right through the lower intestines. 

Allosaurus roars in pain as she crashes to the ground. Stegosaurus turns her head to see the results of her tailwork. After seeing the predator fallen, she turns back to the herd and walks off to rejoin it. Hopefully she can make it in time before more predators appear.  She doesn’t stay to finish off her nemesis-as long as she’s in no immediate danger, she‘s going to rejoin her group.  The search for food and water is far more important than petty revenge.

Allosaurus slowly gets back on her feet. It’s over for her. She could pursue, but the next blow could be pierce her neck or her chest. She’s not going to take more chances. The pain is too great. She’s too tired, too badly hurt, fighting off shock and bleeding badly. She’s not long for this world at any rate, although she doesn’t know it. She’ll make one more kill and have a few more meals before she dies, but within the next month, she’ll be dead. The horrible injuries will compound on each other-fecal bacteria already is entering the blood steam and spreading to the other wound.  The remainder of her life will be spent in agony-the bone has been torn, and instead of repairing the bone will swell and abscess.   She’s already bred-her descendants will rule the next million years, but individually she’s doomed
.
Perhaps the next generation will see another duel, or the next. All that is certain is that Allosaurus and Stegosaurus will continue to glare at each other across the millennia until both species are extinguished.  Next time, we shall cross the channel and see the descendants of Allosaurus and Camptosaurus  as they enter the Cretaceous.








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