295 million years P.E. the world is changing fast. Where once were polar forests are once more tundras and snow, and even tropical regions are now dominated by dry grasslands, the rainfall no longer enough to sustain groves of trees. Changes to the world were already beginning to occur 5 million years ago, as global sogland, a sprawling wetland biome, was replaced with savannah with dry land and scattered trees. Serinarcta's primary biome becomes the flatlands, a continent-spanning steppe landscape, maintained by fire and low rainfall. The flatlands are so named for they lack distinguishing landmarks. Cementrees, though not extinct, are now less common; most sky islands that once towered over the land are now extinct and eroded away, the rains inadequate to keep them alive. Virtually all hills formed before the hothouse from the brief volcanic resurgence of the great thaw have worn away. With much of it now lacking even in isolated trees - for taller plants now thrive only along water courses and in low-lying remnants of lakes and the collapsed remnants of caves - this is truly a flat and featureless world. But it is still early in Serina's decline, and life has had time to adapt. The flatlands may appear sparse, but they still support abundant animal life, especially in herds of grazers and those hunters that still chase them in the never-ending balance of predator and prey. Life becomes harder than it was, and ferocity and tenacity are useful traits to have. But intelligence and cooperation, the hallmarks of Serina's most complex life forms, are not going anywhere yet. 

Life, in all its ups and its down, still goes on in the final stretch.

Most life that cannot shelter below ground for the worst of the dry season now travels the landscape in endless migration to follow the diminishing rains.

Brindled birdbears are one survivor species which has come through the end of the hothouse. They belong to a groups of gravediggers that became firmly adapted for constant upright bipedalism, with nearly vertical spines and long legs that lend them an uncannily human resemblance, especially at a distance. The wanderwalker is a litttle shorter and less robust than its hothouse ancestor, adapted to survive on limited food in a more arid climate, but it is by no means small. Its six-foot height lets them watch the horizon for food or for danger, peering over grass and scrub and spotting distant wildfires in time to flee. Strong claws are used to good effect for self defense, but the wanderwalker's first response to danger is to run; able to reach speeds of 25 miles per hour on their hind legs, they are not as fast as many animals, but like humans the have especially good endurance and can maintain their maximum pace for long periods of time. With a head start, they can outrun many predators that rely on shot bursts of speed and ambush to bring down prey, and they can also use this to their advantage to catch prey on the open steppe where it has nowhere to hide, chasing it down over hours until it is exhausted.

Wanderwalkers are omnivores with both specialized and generalized ways to find food. They still hunt and kill vertebrate prey, but are also more opportunistic ant-eaters than their ancestor, using their talons to break open nest mounds across the flatlands like their earlier but less fortunate relative the barebilled birdbear did in the hothouse forests. They are protected from stings by thick feathers and scaly bare skin. Plant foods eaten include seeds and roots and tubers dug from the ground; the nose of the animal is also attuned to the faint scent of water, and it is a keystone animal for its ability to detect and dig up deposits of hidden groundwater to open up small waterholes in the landscape which can be used by other species. Wanderwalkers have a high need for drinking water, for they also use it in a novel way to keep cool. Wanderwalkers have evolved sweat glands from the follicles at the base of each feather. In heat the feathers are fluffed out and sweat is transported up along the length of each hair-like plume through capillary action and evaporates, cooling the air near the skin as it does so. To help ensure it has enough water to spare for this purpose, the animal can store up to three gallons of water in its crop, a pouch below its throat, swallowing it over time to survive up to five days without access to a water source.

Though their uncommon upright stance may suggest the wanderwalker is a sapient animal, these animals lack such complex cognitive capacity. The limit of their ability lies somewhere between bears and great apes, with their social behavior having some things in common with both. They are social but often restricted in the size of their groups by limited food resources, and most often occur in pairs with or without a single young, that stays with their parents for years to learn necessary life skills. Their memories are excellent, letting them recall sources of water on the endless landscape they travel, and they are capable of tool use like their predecessors, though it is more often limited to use of pre-made items, such as throwing stones at prey, and less often involves making their own tools. Culture exists in the form of hunting and foraging methods taught to their offspring and passed down through generations. Wanderwalkers lack a sense of territory, and so are neutral to other individuals except around kills, which they will defend from interlopers if the food is in short supply. Larger kills, however, may be shared with a submissive stranger in an example of affiliative behavior, in which one wanderwalker will share with another under expectation it will return the favor if they meet again.

~~~

Flutterfoxes were among the very first creatures seen in the final stretch. Some face the global climate change at the end of the hothouse better than others. Grassland-dwellers survive with ease, whereas forest-dependent species now struggle, with most unable to adapt to the flatlands and pressed into increasingly fragmented refuges. Now as plains expand across formerly wetland and jungle regions, pixies, whose ancestors recently flew over the seaway to the north, experience a population explosion as they follow the new grasslands far and wide over Serinarcta. It isn't the grass that they eat, nor its seeds. No, pixies are predators - fierce enemies of insects, such as crickets and the larvae of beetles, which eat the grasses. Each of these animals is a ravenous eater, able to consume more than its own body weight in prey each day. Yet as this tiny species of flutterfox weighs only .75 ounces - so small that three pixies could sit comfortably on one finger - the total quantity, per individual per day, is modest. 

But pixies don't usually live alone. They are highly social, living in family groups which are nomadic, following temporary booms of insect numbers across the land. They are strong fliers, able to cross expanses of unsuitable habitat in search of food, but they forage near the ground. Climbing and clinging to the stalks of plants, they scour them root to shoot for bugs which they snatch in their narrow jaws and chew up well before swallowing. Feeding peaks at dawn and dusk, with the little creatures seeking shade at midday and roosting through much of the night, tightly bunched together in grassy tussocks near the ground.

Though an average pixie clan is three to ten animals, they are well-adapted to make the most of increasingly seasonal rains which can transform a dry plain into a meadow of green leaves and flowers in just a few days. As soon as rains begin, the pixies gather to breed explosively. They pair up and begin to weave complex basket-like balls of dried grass leaves suspended about 10 inches off the ground, intertwined with the living grasses. It is in these nests in which they raise their young. Pregnancy is just 19 days, with litters of up to eight young born naked, hairless, and no bigger than a lima bean. But the babies grow extraordinarily quickly as both their parents make non-stop fetch trips to collect caterpillar-like grubs and swarming winged crickets, which they chew, swallow, and regurgitate as a slurry which is easily eaten by the tiny kits. 

The litter leaves the nest within thirteen days, fully-furred and with nearly-developed wings, and thereafter they make longer and longer forays each day until by 20 days of age the kits take their first flights. They are fully weaned by 35 days of age, at which time their mother will have given birth again if conditions remain favorable, having as many as three consecutive litters before the grasses go dry, the insects move on, and so too must the pixies. Older litters help to feed younger ones, and the family crowds together into increasingly tight nests during the night, which the male attentively expands as necessary until they are as big around as a cantaloupe and may hold some 30 roosting adults and juveniles of varied age. During the peak 6-8 weeks after the rains first begin, they form swarms of many thousands and their fluttering movements make the grass shimmer with iridescent color, with flocks bursting up into flight as larger grazers pass by them. Predators now gather to hunt the young and unwary, forcing the horde to break up into much smaller bands as the nesting season ends, and by the next breeding season, only about 1/10th the numbers will remain to repeat the cycle anew. But pixies are far from the only swarms that fly across this new biome, and even in their absence, there are others to take their place in the skies.

~~~

Mowerbirds have long had countless enemies, yet they were so successful through the hothouse that their numbers were hardly impacted. Through the entire period, there had always been enough green food to support their great flocks of billions.

But the hothouse age is over now, and those days have gone. Drought, chill, and increasingly unpredictable weather mean that the booms are now followed by terrible busts. Birds adapted to endless food resources now find that things don't last. They form super-flocks that travel thousands of miles over the plains in search of green leaves and seeds to sustain themselves, sky-darkening clouds that take days to pass by. They descend like a plague, eating everything in their wake and stripping the ground bare. Once a keystone species that improved biodiversity, in this climate, their wide-ranging search for rare greens is now damaging to the environment. They rip the vegetation they find up by their roots, letting fertile soil be blown away in the wind with nothing to hold it in place, leading to desertification of the land. In the end, hundreds of millions of the birds may still starve if they can't find enough to last until the return of the spring rains, leaving behind only desolation in their wake as less mobile animals lose their food sources and cover vital to their survival. In the final stretch, the mowerbird is a force of destruction. 

But nature doesn't typically allow an organism to be this way for long. The concentrated, migratory nature of these late-surviving mowerbirds means that its difficult for predatory animals to depend on them; they may be here today, but 500 miles away tomorrow. It is so that for some mowerbirds, their biggest threat now comes from within. When the swarming mocust gets too numerous without enough to eat, they start to hunt their own kind.

The swarming mocust first appears to be a typical final stretch mowerbird, its colors much more subdued than earlier species due to the drier and colder landscape being much less green. Typically it is a grazer as an adult, while chicks are fed insects. Always social, they disperse and form smaller breeding flocks when conditions are good but gather in shockingly large numbers when they are not, like locusts, and begin traveling to find resources. Breeding occurs sporadically and not annually, only when the rains come at the right times and produce widespread flushes of green grass to feed the adults, and a few weeks later grass-eating insects to feed their chicks. As long as chicks get enough to eat, they grow up into herbivores, which are extremely gregarious and spend most of their time not spent feeding in close contact with others: allopreening, snuggling, and roosting in physical contact at night. But sometimes, there is a failure in the food supply during the nesting cycle, and many younger chicks begin to starve. Those which get enough to survive, but less than they need for growth, become more aggressive almost immediately, after as little as a day of calorie restriction and if this stress continues for just a couple of days, striking behavioral changes begin to occur. From any time from as young as 5 days of age to as old as 16,  nestlings deprived of adequate food begin violently attacking weaker nestmates and shoving them down to the ground, so that ultimately only one single largest chick remains in each nest. This first increase in aggression occurs purely to reduce competition for food brought by their parents. If by removing their rivals they find themselves well-fed again by them, then this may be as far as it goes; they can regress back toward a more docile demeanor, and develop into typical herbivore adults.

If they remain stressed for as little as four days of food shortage however, chicks that have started undergoing the behavioral change due to insufficient supplies of their traditional nestling diet will begin to develop permanent, physical adaptations. These chicks will begin changing from the typical appearance of all young nestlings, with small plant-cropping beaks, and very quickly develop enlarged, sharply-cusped bills with long "teeth." This transformation is a result of epigenetics; different expressions of genes that occur under varying environmental conditions; prolonged food stress and crowding serve to turn the mowcusts into violent killers. From the moment they are able to fledge the nest around 2.5 weeks of age, these fledgelings now begin seeking out chicks in nests besides their own, and kill them directly, rather than merely pushing them out of the nest. They target them with a savagery that may stun onlookers, biting their violently along the head and chest until they are bloodied and torn. New fledgelings like this still cannot feed themselves, so this behavior serves only to remove competitors further: unrelated adults will likely feed the adolescent killer if their own chicks have disappeared, and so it can exploit multiple sets of parents in addition to its own. The young carnivore progresses within just another week or two to true hunting, however, as its beak hardens and it learns to dismember and feed on its victims. It will continue to beg food from any adult as long as it can, but from four weeks of age it is both able to fly and capable of fending for itself. Its fate is now set in stone: it will from then on out be a cannibal. 

When the flocks leave the nest site and become nomadic, these carnivores stay with them. As adults they are about 20% heavier and have larger beaks, but these differences do not seem to be obvious to the rest of the flock, which do not regard them as strange. And the carnivores don't draw attention to themselves during the day, either. They fly along with the group, and they land when they feed on the grass. But with the ridges on their bills sharp and hypertrophied, they can't cut leaves. While the rest graze they may catch insects or the odd small animal, but mostly are biding their time until the flock goes to a tree to roost for the night. Then, while most of their fellows clump together in tight clusters on the branches to roost, the carnivores keep their distance, both from the herbivores and from one another. They are both behaviorally and physically distinct, and are repulsed by the close contact and social affection their kind normally enjoys. They hiss and peck others that try to push in close, ensuring they have a pocket of personal space all to themselves, and then they wait for darkness to fall, and for the flock to fall asleep. Now they will do their hunting. Carnivore mocusts have larger eyes than the typical form, sometimes by as much as 30%, and see well in the dark. They quietly leave their perches and approach the others as they sleep, grabbing them by the throat and pinching off their airways to silently kill them. They gorge every night this way, each carnivore taking one or two of its own as prey, before returning to their solitary roosts before dawn, the survivors none the wiser to where their peers have gone.

Carnivore mocusts can survive droughts and scarcity that cause massive population declines in their herbivorous counterparts by eating meat instead of plants, and this may be why the alternate genetic expression that produces them evolved. But they can also prevent famines by serving as a predator that can prevent overpopulation in the first place. Mocust populations as well as individuals are healthiest with a small percentage of carnivores among them, which target the old, weak and sick, as does any predator. The ratio of the two morphs to one another typically rises and falls opposite of the other, as more carnivores are born during conditions with limited plant food, and these then hunt the remaining herbivores until the population is more in line with available food resources. A small number of carnivores in the nest colony improve the survival rate of chicks overall by culling the weak ones and driving away other nocturnal predators, but when they become too numerous in the flock relative to the others it becomes harder for them to hide in the crowd, and their surviving prey becomes better at detecting and defending against them. In these ways, the carnivore's life strategy only works if there are only a few of them in the population, and past a certain threshold, the carnivores will no longer find it efficient to hunt within the colony and be forced to pursue other prey, or else begin to fight amongst themselves for food and frequently kill each other, lowering their population again until the cycle begins anew.

Both morphs reproduce in the same colonies and even interbreed, as reproductive drives can overpower predatory ones and allow pair bonds to develop between carnivores and herbivores they would otherwise kill. Chicks born from carnivores will default to being herbivores again unless also subjected to overcrowding and food shortage early in life, as the carnivore morph is not a directly heritable trait but rather an alternate expression of genes present in every individual of the species. In this way a single species can be perpetuated through two very different ways of life, which can give rise to the other as conditions require, letting the species overall weather difficult, changing circumstances year to year.

~~~

Though in some ways made less apparent by the highly dramatic adaptations of survivor species such as the swarming mocust, the ongoing aridification of Serina after the hothouse is still causing another mass extinction of plant and animal life. Forests have receded rapidly to tiny fragments of former range. Lineages which evolved in the long, stable hothouse world often struggle to adjust to these changes - a recurring theme in the story of life upon Serina which repeats again in the final stretch.  Many formerly dominant groups are in spiraling decline, especially those which were the largest, as they now struggle to find enough food to support themselves.

But there are always others waiting in the wings for the mighty to fall - the smaller, more adaptable species that can take their place in the sun only once their long-time rivals fall out of power. In the final stretch, the mighty giant aukvultures - the largest carnivorous birds ever to fly the skies - have lost out. They became victims of their overspecialization, namely their huge sizes that relied on abundant large prey. Later species were often so large and robust that they were poor hunters and relied mostly on stealing carrion from land-based predators; when it became scarce, they dwindled. In their stead, a new scavenger now soars the global skies: caracudas, vulture-like tribbats evolved from the aeracuda lineage. These tribbats, the most morphologically conservative dividopterans, persisted throughout the hothouse in limited diversity in the shadows of far bigger fliers, but now find room to reach higher.

Caracudas are among the biggest tribbats of the current era, with wingspans of seven to eight feet, though they are much smaller than hothouse giants like the seademons. They have long wings suited to catch updrafts and soar at a height over the plains, crossing continents in their travels, looking for the carrion which makes up most of their diet. Their eyesight isn't exceptional, but their sense of smell is unparalleled; they have evolved a pair of specialized nasal crests unlike any other animal which enlarges the sensitivity of their nose to pick up isolated scent molecules on the wind substantially. This crest is comprised of two enormous nostrils that connect with an open septum, allowing air to flow in one and out the next over a damp mucous membrane. Muscles control the direction of each crest to finely pinpoint the direction a scent originates, as well as to flatten them down on the snout when needed while flying to clear their view, and to seal them off while feeding to keep out blood and flies while reaching their hairless heads into carcasses. When anything dies on the grasslands the caracudas are always the first to know; they gather from miles around and descend upon it, shrieking and snapping and tearing into the corpse with ravenous delight. They eat only the soft parts, tearing out the organs and viscera with their long, toothy jaws and gobbling up what they can before more powerful sawjaws and other terrestrial carnivores arrive and finish cleaning up the harder pieces. These fearsome-looking tribbats might seem vicious, but are in fact meek and remarkably benign. They flee a kill as soon as a stronger animal appears, and won't risk a fight that could easily cripple their fragile wings. Occasionally they arrive before an ailing or wounded creature is dead; they are reluctant to attack anything that can potentially defend itself, and so will often gather silently in an apparent vigil around the ill-fated beast until its last breath assures it has passed on. For this unusual behavior, they gain their latin name; the angel of death.

~~~

Some flutterfoxes are also long-distance travelers. This second flying tribbet group, they are distinguished from tribbats like the caracuda by their wings, which are supported by three independent digits lined with zipped-together bristles, and resemble feathers with a shaft of bone. Flutterfoxes evolved in the hothouse jungle, but as we saw with the pixie, some species have adapted to a world with far fewer trees, becoming stronger fliers and more competent at moving over the ground, which they do by hopping on their single hind leg, in contrast to the tripedal tribbats. While this is a fairly unstable manner of movement, flutterfoxes' small size and very lightweight bodies make it functional, and by fluttering their outstretched wings for balance, they rarely trip even at high speeds.

The most-adapted flutterfoxes toward life in the new, unpredictable global climate are not pixies, whose numbers rise and fall dramatically, but another group called rovers. They are omnivores which feed on nearly anything small that they can find, including seeds, fruit, insects, molodonts, murds, and small flying birds, and they have long legs with which to spring across the plains to find food. They are also powerful flyers, able to maintain sustained flight for long distances, and many species are strongly migratory. Common rovers have a very wide range, for they breed in the antarctic circle upon the tundra south of the austral swamp, taking advantage of the short, productive summer season. When fall arrives, they fly north across the seaway to "winter" in the flatlands of northern Serinarcta just as the seasons shift and spring returns to that hemisphere, effectively skipping winter entirely.

Breeding pairs of the common rover, which is lifelong monogamous, nest alone on the tundra in a simple scrape in the ground in which the female initially rears her pups, usually born as twins. Both parents feed and take turns guarding them, covering the nest with grass if they must leave so hide them from sight. They are strong enough to run along after their parents across the ground at 2 weeks of age and begin practicing for flight soon after, though their wings are not well-enough developed for it until five weeks of age. By the time the short polar summer comes to and end, they are nearly the size of their parents, and strong enough to follow them north on migration, at which time rovers gather in large flocks of thousands for safety as they travel. They mature quite quickly, and even yearling common rovers begin pairing up and reproducing as soon as they return back to the tundra in their spring, at an age of just nine months.

~~~

It's not just rovers that fly to more favorable climates. An exodus is underway, as animals from north and south migrate to more hospitable equatorial zones; some instead descended downward into low-elevation craters, the remnants of drained wetlands - but now become marooned there as the outlying landscapes dry up and become uninhabitable for them. Even so, for now hothouse life can persist in these places little-changed, but for those unable to adapt soon, the end is now in sight, as these havens will ultimately shrink, fragment, and break down over the next five million years.

There are some animals naturally faring better in the aftermath of the hothouse than others. The fliers - birds, tribbats, and the flutterfoxes - can most easily cross the vastness of the world and find new homes as old ones become unsuitable. Where grounded animals may take many years to cross continents, even many generations, some fliers can do in a matter of days. With everything becoming unpredictable, there is a growing selective pressure to be more mobile in the event that a migration becomes necessary. Flutterfoxes, once creatures of the jungle, rapidly develop longer wings to carry them on lengthy journeys. But now they are not alone in their rapid ascent into the skies. Just a few million years after their first tentative flaps in the air, they are followed by another. A lineage of birds which lost all capacity for flight over 40 million years ago has done something never before seen: they have regained the ability, just in time to face the end of the world. Those birds would be the skungarus - part of the widely successful skuorc radiation that took the world by storm over the hothouse. Flutterfoxes have flown for just ten million years, yet they are not the newest lineage to evolve flight anymore. There is another, making the great leap so few have managed, and doing it with hardly any time left to spare.

The pteroo is a very remarkable bird, for it flies on wings with no feathers, but instead a membrane of skin, like a tribbat. It is the direct descendant of the kangglider, one of two such divergent lineages that have exaggerated the gliding ability of that ancestor. The other specialized as a glider, maximizing its lift surface, and careening from cliff to cliff. This one, though, remained on the open plains. To maximize its distance in the air between leaps, its bounding ancestors learned to flutter their wings. Their third digits elongated, giving them greater lift with each thrust. Sometime around ten thousand years ago, the first pteroo was born with a sufficiently long wingspan that it did not need to rely on the wind currents alone to carry it. It could flap its wings and truly fly. And fly it did, crossing the world far below, its descendants ultimately leaving the flocks stuck down on the ground far behind. Today, they have spread worldwide in several populations, each one having found its own hospitable patch of refuge that those not gifted with the means to fly may have not been able to find. Now, each of them one is started on its way toward speciation. 

But there is a catch to the pteroo's newfound freedom of flight. It is a fleeting gift available only to the young. Pteroos can only fly for the first ten to twelve months of their lives. After this time, they become too heavy to achieve proper lift-off with their lack of a keel bone to support larger breast muscles, and can from then on only glide shorter distances in order to increase the length of their stride, like their parent species, which they eventually grow to closely resemble. Their chance to escape hostile climate change thus depends on their ability to quickly rear offspring. If things become rough, it will be they, and they alone, which will be able to escape it and move on without their parents. In this way, the flying adolescent mirrors the life history of such widely unrelated birds as the rasps. Like them, the different life stages of the pteroo differ also in their niches. Adults are heavily vegetarian, and graze the plains for a leaf-heavy diet, while the winged young are active insect-hunters.

As the world shifts and the hothouse world becomes a forgotten memory, the pteroo now stands a much better chance at staying in the game of life than most other land animals - as long as they can continue to find hospitable habitats before each individual's time in the sky runs out.

~~~

The pteroo is fortunate, for even if its flight is a temporary means to travel, there are very many animals, even those who once flew, that are no longer capable of aerial journeys. And so these are the earth-shakers, the vast herds that migrate over land. They come in all shapes and all sizes, but it is the giraffowl which are doing especially well in this new era, one in which most of the fast and agile thorngrazers that darted all across this land just five million years ago have vanished - or been changed irrevocably, as has occurred with some of the unicorns, now fierce carnivores very unlike their ancestors.

The dromanary is a giraffowl native to the dry plains of southern Serinarcta in the early final stretch. It is one of the most perfectly grasslands-adapted species of its clade, many of which have died out with the shrinking of the forest, and is a mixed feeder that can both browse low woody vegetation and graze low-growing herbs and grasses. With long legs and high endurance, dromanaries partake in long migrations  - sometimes over 100 miles in a single day - to follow flushes of greenery that follow unpredictable rain, which they can smell from a long distance away. They are hunted by a variety of hardy predators but are not easily killed, being better at defending themselves than they would seem. Both sexes have only small, forked bill crests but use them to good effect; by twisting the neck and lunging to the side, they can stab enemies, using their solid bony horns like a mace.

The dromanary belongs to a lineage of giraffowl with completely flightless chicks and descends from the fowlpaca; it shares an ancestry with similarly-adapted crownprinces of the hothouse, and with other related and contemporary species that also live on the flatlands. Fowlpacas were already pre-adapted to cooler, arid grasslands, for they evolved on the firmament, a biome that resembled the new flatlands. When the firmament eroded, the fowlpacas easily colonized the ground below at a time where most of its native species struggled to adapt. They became a success story, and now they have diversified.

Their real key to success is their parental care and protection. Their young are incubated in the ventral pouch of the female, so that they are not threatened by cold or by predators, and emerge from their pupal sacs with vestigial flight feathers which fall out in a few weeks. Instead, the young remain in the pouch and feed on a nutritious oily secretion produced by skin glands there for several weeks before they begin to climb out on the female's back; the consistency of this material is similar to butter, and it originates from oil glands that helped to keep the pouch lubricated and moist for the developing pupa, which evolved to produce an excess of this grease as a way to feed the young a food high in protein and calories while keeping them close by the parent for safety. Chicks continue to intermittently re-enter the pouch to feed on "pouch grease" for several months, before they eventually wean fully onto a plant diet; because of this high dependence on the mother for resources, broods are very small in the dromanary, just two or three chicks once a year. Adults can survive food shortages by storing fat in a camel-like shoulder hump, which can last them several months without any fresh plant food or allow a female to raise her litter to independence even on a very poor diet, if she was able to feed well the year before.

~~~

Capricocks are relatives of the dromanary, though they sit much closer to the crownprinces. That they don't depend on trees for food, like those most often did, is their main advantage; with short, robust necks, these birds had already evolved to feed on ground-level vegetation back in the hothouse age, before the reduction in forest coverage pushed them out onto the plains of a colder world. Poor-flying young, already competent at running on the ground from infancy, and which could learn to stick close to the adult for protection and warmth were another. All of these traits are present in one of the descendant lineages of these small, pugnacious birds, the capricoxen (capricox, for singular.)

Climactic capricoxen are sturdy, bison-like giraffowl which dwell in large herds on northern flatland and tundra habitats. They have short legs and huge heads and necks, making them low to the ground, difficult to push over, and incredibly strong. Both sexes have wide, rounded bill horns, as they are used as shovels to push aside snow from the ground over long winters in order to graze. Through the winter and the spring, and partway though summer, capricoxen all look alike, and sexes lack differentiating external features. But toward the end of the growing season, when the first fleeting chill of winter's not too distant approach fills the air, some males begin to undergo a rapid change. They molt their thin summer plumage first, gradually shedding their pale feathers and replacing them with a longer, dark, almost black coat with sharper white highlights on the face and underside. Then comes changes to their bill, as it flushes a bright shade of red and begins to grow additional sharp prongs and tooth-like ridges. Within just six weeks, such males are transformed; the forward-most spikes of their crests elongate into pairs of wicked, spiked barbs, as small serrations on their bills become grossly overgrown until they resemble the fangs of some terrible carnivorous beast, lending it a vicious, slashing bite. But the male capricox, as it enters breeding condition, does not gain a taste for flesh. It becomes incapable of eating anything at all. As a descendant of the annual morph of the pronghorn capricock, male climactic capricoxen will go through only one breeding season in their lives. Relying on energy stored as fat throughout the earlier spring and summer, once males enter this state, their bodies are in a race against the clock to breed before they starve to death, as their beaks - sharp and deadly in a fight - now inhibit them from feeding.

It takes three to five years for a capricox male to be large enough to undergo the tranformation into its terminal breeding phase, and this is largely dependent on nutrition. Until that time, males and females are almost identical and don't behave differently. Once it does occur, however, the male's entire temperament changes into a ferocious, hormone-driven ball of rage, and males see red, becoming utterly intolerant of one another in any context. Immature males are effectively invisible; the breeding males don't pay them any attention. But as soon as any begin showing red on their beaks, they begin to fight, and by the time the transformation is complete, they are often already bruised and battered. The males fight violently over control of the herds of females just as they begin to come into season themselves, locking their horns together in contests of strength that can last for hours and slashing at one another anywhere they can get their beaks on. It is gory chaos, because when everyone dies at the end, there is no reason to hold anything back - and they don't. Many of the first males to finish their transformation die well before starvation gets them from the savagery of later-maturing males which take advantage of them in their already weakened state and attack them as they are distracted in combat with each other. The spectacle of the capricox breeding season, which lasts less than four weeks, draws in the attention of predators and scavengers from hundreds of miles around, which need do nothing except sit and wait to eat the dead and dying losers of these contests as they are flung to the edges of the ring.

When the number of breeding males relative to available females is reduced through bloody combat to somewhere around one to twenty, the violence dies down as the competition over mates becomes minimal, and the surviving males lose interest in further aggression. These are the winners, a small fragment of the former herd, those which have proven themselves against the strongest of the strong and come out on top. They have the genes the females want for their offspring, the genes of survivors. The females now accept them, and they now enter a mating frenzy that will last as long as another two weeks, ending in their eventual death from exhaustion. Between 20-30% of all males in the population die in this way annually, timing the end of their lives with the arrival of winter, when food becomes scarce and the females - gestating their chicks in their abdominal pouches - need all that they can get. By removing themselves from the population at this time, they increase the resources available to their mates and their young.

~~~

The capricoceros is the single sister species of the capricox genus. Both clades descend from the pronghorn capricock, which split into multiple species as a result of increased variation within the males of the species, which were divisible into slow-growing, long-lived morphs, and morphs which grew rapidly but often died after mating. Capricoxen carry more genetic contribution from the annual male, and are known for the dramatic transformations undergone by males in breeding condition, which is followed inevitably by their death from exhaustion and starvation. The capricoceros, meanwhile, evolved primarily from the perennial male, and does not undergo significant seasonal changes in appearance. The split of this species was driven by differing female preferences toward one type or the other, and their eventual separation into different habitats after the hothouse.

Capricoceros live further south than their counterparts, in the dry, temperate plains of central Serinarcta. With less severe winters than the poles but milder radiation than hits the equato here, it is a species of the final stretch "goldilocks zone", that range of latitude is most habitable in this period.  Because the male capricoceros doesn't devote all of its energy toward one single, spectacular breeding season, it can afford to grow more slowly than its relative, only being sexually mature around five to six years of age, and also to reach a much larger adult size. This species can weigh over 1,200 pounds, and is both longer and more low-slung, a grazer of grass and near-ground vegetation, including thorny, hostile plants that few other birds will tackle, thanks to the facial protection it is provided while feeding with its huge cropping bill. Its niche is similar to that of the large, Mid-ultimocene thorngrazers that differed quite a bit from their current descendants.

Capricoceros are large enough, and well-defended enough with their huge, forward-swept bill crests, that they can afford to travel in much smaller groups than their crelatives, and males are primarily solitary outside of mating. Females live in small herds of five to fifteen, which collectively guard the vulnerable young, one of only a handful of giraffowl which have no power of flight even in their infancy, and which are born without wing fingers - though they are present in development, they are reabsorbed before the chick hatches from its pupal sac and leaves its mother's pouch. Male capricoceros gather to fight over breeding opportunities seasonally in the autumn but these contests are not nearly as deadly as in the capricoxen, for males are generally long-lived and so have a limit to how much they will exert themselves before retreating from a fight; most likely, they will get another chance the following season. Males continue to grow until at least eight years of age, and so the oldest males ultimately have the greatest reproductive success.

~~~

There is a rare phenomenon sometimes observed, where their ranges overlap, of a hybrid between the the capricoceros and the climactic capricox, which can still interbreed despite significant behavioral barriers that usually prevent it. Only a few million years separated, living offspring can be born from unions between male capricoceros and female capricox (the opposite combination does not occur, as the very large female capricoceros will not accept a smaller mate.)  Hybrids are sterile, but their size exceeds that of both parents as a result of hybrid vigor and a lack of size-influencing genetic factors normally provided by the female capricoceros, and so hybrid males can weigh almost 2,000 pounds. These males start life with a docile temperament, but will eventually turn monstrous and deadly, for they inherit the mating behavior of their smaller parent, but reach enormous sizes before then, producing animals that as adults are exceedingly violent and destructive. So ferocious and abnormal is the male of this rare hybrid, that it is distinguished by a name of its own: the "calamitous capricox." 

While its female counterparts exhibit gigantism, they are otherwise not distinct, nor especially aggressive. The male, however, is astonishingly aggressive at maturity. Unable to actually sire offspring, the sterile calamitous capricox shows courting behavior that is a confused mixture of both parents, and so generally are repulsive to females of either species. These males may take as long as seven years to be mature, but eventually will enter a rut which then lasts until the end of their lives, during which they become among the most aggressive, and ultimately most dyfunctional, of all animals ever to live. They are transformed into mindless killers, compelled by a massive surge of hormones that drives them to fight with even greater abandon than the capricox. They kill other males in droves, easily winning all contests by their sheer size alone, and attempt to to forcibly mate with anything that moves. An overabundance of testosterone causes physical changes as dramatic as their behavioral ones, causing a massive, out of control growth of their beaks and horns. And this is where this animal's existence becomes as tragic as it is horrifying: in the late stages of their rut, they are unable to even close their grossly overgrown mouths, let alone to eat, and frequently splinter their own jaws apart into bloody shards in their hopeless efforts to do so. Such animals must spend the ends of their lives in agonizing pain, and may be blinded as their horns extend down over their eyesight, or even grow into the flesh of their faces.

At the end of their rut, the calamitous capricox will eventually die like the climactic capricox male, but their larger size means they take much longer to succumb to starvation, and their reign of terror may last six months. Blinded in more ways than one, as its condition progresses, the the hormone-fueled violent sex binge of the hybrid may (mercifully) be cut short by its indiscriminate attempts to mate with anything even vaguely similar to a mate, including predators and larger, stronger herbivores that will have no hesitation to turn around and kill it. But most of the time, the animal does not find such a "kind" end. After a few months of aggressive combat and attempts to breed, it merely wanders around in increasing disorientation as its condition deteriorates and it becomes confused and increasingly disabled by the trap grown out from its own body, becoming a zombie-like shell of its former self that can no longer anticipate anything else in life but the arrival of death.

There is perhaps no better example to show that hybridization between related species is not always beneficial; in the case of these pitiful animals, it is now nothing short of a disaster. But this is not always the case. In other instances, hybridization can not only be favorable, but hold the key to survival.

As the continent dries after the hothouse, a lot of Serinarcta's wetland-adapted species decline, becoming restricted to isolated low-lying refugia that are the last to dry out, if they survive at all. But some hold on in the world beyond, thanks to a combination of useful pre-adaptations, and good, old fashioned tenacity. This is true for the golden humpo, one of the largest trunkos still extant, and a descendant of the riparian swamp wumpo. Though its world now, of dry grassland, drought, and aridity, is very unlike the world its ancestors knew, it has survived nonetheless thanks to new genes it has acquired from ancient cross-breeding with the genetically diverse and behaviorally varied swarm wumpo. It has come to resemble, in some respects, one of its earlier ancestor species, the desert wump. The small hump on its back has increased in size, allowing it to store fat during temporary periods of abundance and so to endure months of famine; this fat can be metabolized not only into energy, but also a not insignificant quantity of water, allowing it to go for over ten days without a drink. But the humpo also retains a derived trait that it gets from the swamp wumpo in the form of its dewlap, which still aids it in keeping cool as the animal stands against the wind and this blood-rich flap of skin is chilled as it passes over its surface. The nasal cavity of this species is very expansive, almost balloon-like, and is densely lined with hair-like filaments which filter dust from the air as it breathes, with the additional effect of collecting water vapor from its breathe and preventing it from being lost. 

Golden humpos are social, but like their ancestor, to a lesser degree than many wumpos. A herd of eight is considered large, fifteen is massive, and most groups are only of four to six. Food is not typically available enough, in the dry equatorial areas they live, to support long-lasting gatherings of larger size, though the memory of the humpo is very good, and relatives may meet each other at annual gathering sites near permanent watering holes and mingle together for a few scarce weeks before going their own ways once again. Bonds are strongest between mothers and their male offspring, as this species is matrilineal, so that adult females tend to leave their mothers' groups while males remain.

A single chick is raised by the females alone, with males not partaking in incubation roles; fathers may or may not be present within the same herd as their mates, but males which are present will provide some parental care toward any chicks by protecting them from predators and teaching them foraging techniques, such as how to dig out roots and access underground water sources.

~~~

As more and more life succumbs to the climate, or flees to shrinking remnants of wetland and woodland, the plains grow emptier, even with the remnant herds. There is now an absence of truly gigantic species, for by now the last gantuans, giants needing huge quantities of rich food, have fled to the last places they can find to still support them; they are trapped, and these relictual habitats will continue to shrink until one day they too disappear. But for the hardier creatures that remain on the open plains without them, their world has now become more peaceful.

The ridicupines are descendants of the troxupine which have adapted to the changing environment, and continue to thrive despite it. They are hairier now, with little exposed skin to chill in the night, and they live in smaller groups, since there is both less nutritious food available and fewer dangers to threaten them. The ring of horns along their sides now sweep down and curve up at their tips, protecting the legs and belly completely from enemies when sitting down, like its own personal security fence. The second set of horns on top of the snout is long and lance-like, useful to strike at predators that come from above. Yet without large numbers of cygnosaurs to fend off, their defensive spines - a structure unique to monstrocorns with traits of both hair and horn - have taken on a role besides defense. They are now flattened into disc-like plates that can now be moved in tracts to spread out or lie flat, letting the animal trap heat against the body in cold conditions, and to fan itself to keep cool it in hot weather. While these plates are no longer especially sharp however, don't be fooled - the long hairs which grow between them are, and still easily dislodge into skin if the animal is provoked.

The ridicupine feeds on anything it can scrape up from the ground with its undercut jaw, much like the ice age thorngrazers long before it. Its teeth are stained red, as it incorporates iron from the ground into their structure for strength. Roots and tubers, grasses, and any small animals it stumbles upon are all acceptable fare, as is the bark of isolated stands of surviving trees, which by girdling in this way it now contributes to the decline of. If food is scented too deep below ground to shovel it up in the jaw the ridicupine has evolved long claw-like hooves and is now an accomplished digger, able to unearth rich buried food resources such as nests of small animals seeking shelter below ground from the sun. Like many animals sharing this environment, it also uses its claws to break into the abundant tower-like ant nests that now dot the plains, but it doesn't waste time licking up just the bugs when it's easier to eat the whole contents that spills out wholesale - dirt, larvae, honey, and all.

The landscape has shifted a lot in just five million years, and will do so even more over the ages to come. But the ridicupine is among the few animals that is ideally suited to keep going, and to see what the future yet holds. The hothouse now over, their lineage will be the longest-lasting of the thorngrazers, and after biding their time in the shadows of bigger things for millions of years, the world is theirs to claim once again. But it isn't all theirs, for there are still other herds on the plains, very different in form and in function, but no less well adapted to the flatlands. For some species, there has been almost no need for major anatomical changes to continue to thrive.

~~~

In a world of trunkos and metamorph birds - only speaking for avians,  the sparrowgulls stand out as the odd ones out for being morphologically primitive and, for the most part, little changed since Serina's beginnings. The basic perching bird form, as well as the even more ancient shorebird and ratite-like body shapes, remain effective for survival now as so long ago, and sparrowgulls continue to survive the ever-changing world they live in more through behavioral changes than stark physical ones.

Most of the time.

Some sparrowgulls are outliers. Though they are inevitably still more "bird-like" than many contemporaries, not all sparrowgulls have remained small "ravens" and "gulls."  A few lineages of these birds have, over the eons, managed to lose their powers of flight and reach substantial sizes; pretenguins, for the most part, have held records for both the aquatic and terrestrial extremes of size. 295 million years PE, though, a new sparrowgull takes the claim for tallest species, the 14 foot high horstrich of the southern plains of Serinarcta. A descendant of the carriageoose itself evolved from the early hothouse chariot, the horstrich is, despite its height, an omnivore that eats mostly grass, slicing it with ease with a sturdy serrated bill. Social and more intelligent than their smaller lookalikes on Earth, horstriches live in herds in which a sentry is always alert for predators with its eyes high in the sky, while its fellows dip their heads down to the ground to feed. The thighs and lower legs of the horstrich are featherless, which helps keep them cool in the heat, but their heads, necks and upper bodies are feathered, and so shade these exposed parts from the harshness of the sun. Both sexes of this 900 pound bird are somewhat colorful, females being a mossy green with a pale lilac head, while that of the male is covered in deep blue feathers.

Horstriches have several unusual adaptations that are not seen in other sparrowgulls, but which are built off of common adaptations seen in all species to carry their eggs. They have lost the plumage of the lower wing and evolved a more mobile featherless "hand" which resembles a mitten, and can curl up and inward from its tip like a short tentacle thanks to a lack of ossification in the finger bones, which allows it better dexterity when picking up and holding its eggs. The alula of the wing is also fleshy and supported with a cartilage rod, forming a thumb with a concave "thumbprint" that provides additional grip on the egg. These birds have lost the need to nest or incubate their eggs on the ground, and females brood their clutches of two eggs by holding them against a bare patch of skin on their chests, where they are insulated beneath long plumes which grow from below the neck. The arms of these birds are very long and muscular, yet are specialized entirely for these roles, and the bird does not seem to use them for anything else; a specialized locking tendon in the elbow lets them hold their eggs up against their chest for many hours at a time without expending energy.

Female horstriches incubate their eggs, but it is the males which take over childcare as soon as they begin to hatch. Unlike the female, he has long, very stiff "flight feathers" along his upper arms, which point upward and when pressed against similar upright tail feathers form a basket-like accommodation on his back in which he places his newborn chicks with his beak, gripping them by a loose nape of skin on their backs. Males may have multiple female partners, and so can raise up to eight chicks this way, though three to five is typical. Despite the resemblance of the adult to an ostrich, the altricial chicks of the horstrich are unable to walk for weeks after hatching, and in this way are more like those of other sparrowgulls and the ancestral canary bird. They are wholly dependent on their father for everything for at least a month, and are fed a regurgitated milk-like fluid produced in his stomach until they are able to digest a coarser diet of grass and insects that they will begin hunting when they learn to run on the ground around 4 weeks of age. Young will continue to seek shelter on top of their parent for as long as three months before they are too large and are denied further access; they remain with him for at least nine months, trailing close behind on the ground, and are well-tolerated by him even after he begins raising a second, younger brood. Though the females in the herd will provide sentry duty and alert the chicks and the males of predators, they do not protect their babies, and this job falls entirely on the male. His speed protects him from most of them, and even with chicks on board he can reach speeds of 45 miles per hour. The horstrich has only a single toe on each foot, covered in a protective nail, and has lost both surrounding ones over the eons to facilitate the most limited contact with the ground with each step to maximize its speed. If running is not an option, however, the horstrich can kick its enemies with over 1/500 pounds of square force per square inch, easily enough to break bones and cripple unwary hunters. These birds kick out forwards in a rapid series of alternating strikes, each one coming in at some 200 miles per hour; thanks to its massive leg muscles, its kicks are about as damaging as those of a horse, even though it is a lighter animal.

~~~

Other derived birds still persist after the hothouse too. Though the forests are retreating in the final stretch, replaced by more drought-tolerant grasslands, the scarreots are one group of woodland creatures that have come through the changes so far relatively well. Thanks to their behavioral flexibility and their remarkable beak structure, not only larger scarreots like the carnacaw and the trowelfowl of the craterlands have survived, but also small species like the bludgerigar, which were already adapted to live in more open, savannah habitats. Among its descendant clades are the bonkkeets, ground-dwelling scareakeets adapted to get on just fine even without trees to nest in.

Bonkkeets, like their ancestors, are small, mostly carnivorous birds, and they use their beaks like short-distance slingshots to punch prey animals and stun them with concussive force. These birds can still fly, but do so only when pressed, and primarily hunt on the ground. They have developed shorter legs and squatter bodies, adaptations that allow them to enter molodont burrows and prey upon the inhabitants. Their prey can do little to fight them in the confined space of their tunnels, in which any approaching will be struck head-on by the bonkkeet's spring-loaded bill. Instead, the molodonts have learned to defend themselves by attempting to collapse their tunnels if the bonkkeet enters. They may hope either to hide themselves from its sight by sealing themselves away from their enemy, or they may try to to kill it by burying it alive and sealing it within a central tunnel of the burrow. But the bonkkeet, in turn, has become a better digger in its own right, able to move earth with its beak like an excavator, so that this may only slow it down - if the prey are lucky, for just long enough for them to evacuate one burrow and escape down another.

Bonkkeets are distinct from most scarreots for their strong degree of sexual dimorphism, which goes hand in hand with their lack of pair bonding. Males are brightly colored, sometimes with feather crests or other ornaments. Females are mottled brown, sometimes with subdued green or yellow highlights that provide them camouflage along the ground. These birds are solitary outside mating season, when the females seek out males as they display near their burrows, emitting low clicking calls and doing amusing bouncing dances. Though all bonkkeets live in burrows, only the aptly-named burrowing bonkkeet usually constructs its own; the rest simply take over those of their molodont prey. Breeding is somewhat risky for males of all bonkkeets, as females are also bigger than them, and can potentially cannibalize males that she does not deem worthy. More often, though, the danger is simply that she will see his burrow, decide it is better than her own, and take it for herself, evicting him outside. Burrowing bonkkeets avoid this issue altogether by constructing their own display burrow used exclusively for attracting the female. It is dug very deep, with a tightly spiraling, corkscrew-like entrance, and is ideally designed to provide a deep, safe shelter for the female to nest and hatch her chicks. The male now intends to give this burrow to his mate, and she judges his fitness partially by how well he has constructed it. When he finds a partner, he simply leaves it to her and returns to his own far shallower and more simple burrow nearby. There is still a risk, however, that another male might take over his living space while he is distracted, although at least if this occurs, males are more likely to be evenly matched, and he stands a better chance of reclaiming it than he would from a female.

Though bonkkeets are predatory, and are particularly fearsome animals in their size class, they do not indiscriminately kill anything they come across. Some species of mowerbirds seek shelter within their burrows and, astonishingly, the bonkkeet does not harm them or try to evict them. These two types of birds do not compete for food resources, for mowerbirds are more herbivorous while bonkkeets eat little else but meat. While the scarreot could simply eat its home invaders, it has more to gain by tolerating them as an additional set of eyes and ears to watch out for danger. Though a single adult bonkkeet may be well-defended and relatively safe from most threats, this is not true for chicks. Females young must leave them at least once daily to hunt for food, and during this time they are completely defenseless. By tolerating mowerbirds within their nests, their chicks gain protection when they are absent, and in return, the mowerbirds are provided a far superior shelter than they could dig out on their own. These relationships are long-term, and the two partners come to recognize each other specifically, so that not only will the mowerbirds recognize the bonkkeet in general, but will know their specific bonkkeet, and alert their own if an unfamiliar one attempts to enter the nest in their absence, which could result in the death of its young and the takeover of the burrow. Though the mowerbirds cannot harm intruding bonkkeets, they can slow them down and distract them long enough for the rightful owner to return and fight them off. In this way, truly mutualistic interactions have begun to develop in which each partner receives benefits that can ultimately be the difference between survival and death in this unpredictable, fast-changing landscape.

~~~

The sky islands are eroding away in the final stretch as the climate shifts. Forests which once grew at their summits are now stunted, shrubby outcrops growing on ill-maintained remnants of eroding spires whose symbiotic ant trees are dwindling fast. Many of the large animals that once inhabited them have moved down to lower elevations, to the flatlands, but some small, hardy creatures remain. Every so often across the flatlands, a spire rises on the horizon; these are the crumbling cores of the largest sky islands, not yet vanished. They are now dominated by the skyraxes, tiny cliff-clinging thorngrazers which can endure the rough conditions of this post-hothouse habitat by sheltering in crevices to avoid the intense sunlight and emerge at night to graze the remaining vegetation on the crumbling scree slopes too steep and unstable to support the weight of anything larger. Many of their former predators have left the islands - but a new one has ascended from the changing world below. 

As the forests recede away and the plains grow dry, finchworms are forced from the treetops back down to the ground. But the flatlands do not suit most very well, and they seek new high places to find shelter. These long-bodied stoatshrikes are excellent climbers, and with fewer trees to scurry up to seek prey and escape their own enemies, they turned to the shrinking sky islands. The sinuous body of the skyken now lets it hide deep within the structures, squeezing into narrow cracks and fissures which form as the mountain slowly falls apart in the weather without ants to maintain its structure with repairs. Their small size, meanwhile, lets them clamber over the surface of the cliffs of the mountain without setting of rockslides. Thick, pale feathers protect their skin from the sun's radiation, while dark patches around either eye absorb light and keep glare from its eyes as it hunts its prey in broad daylight. They take advantage of the skyrax's need to hide away the day to corner them in their dens deep in the cliffs and kill them. These birds have almost snake-like flexibility in both vertical and horizontal planes, with entirely unfused spinal vertebrae, allowing them to squeeze through narrow spaces and access even the most inaccessibly tight and twisted tunnels their smaller prey may try to find shelter. They strike fast and deadly, avoiding horns and sharp jaws to get a bone-snapping bite to the back of the head with their sharp tooth-like beak serrations. Prey is rarely eaten in place, but rather dragged out and taken away to its own den, where if it is not immediately hungry it will store it away for later deep in the rockwork where it will stay cool and delay decomposition. 

The skyken hunts alone but lives in mated pairs which cooperatively raise their young. Adults are territorial against same-sex rivals, but tolerate other adults if food is plentiful. Chicks are fast-growing and learn to hunt beginning at five or six weeks old; they become independent at six months of age, but don't have to leave their parent's territory until around a year of age, and until then may return to their parent's den to sleep, though they will be expected to hunt on their own by this time. Skykens don't disperse long distances over flat terrain, limiting their range to around a single island, and as it has become more eroded, populations began to become reproductively isolated and to differentiate into subspecies that may now differ in both coloration and size. The largest ones, natives of the westernmost islands of the flatlands, became the best at crossing the ground until they began to meet other subspecies on other islands that have begun to evolve in other directions. Now in some places two forms of the species are contemporary again, with the larger ones hunting near the base of the mountain and the smallest spending their entire lives inside deep rocky tunnels near the summit; they now rarely cross paths and mate, even though their differences are more superficial than genetic, as their habitat preferences now have little overlap, and if they do meet the larger form may cannibalize the smaller.

~~~

The largest land predator of the early final stretch is a roughly one-ton subjugator called the chimera. Named after a beast of legend, the chimera was said to be a fire-breathing beast with the head of a lion, a snake for a tail, and the head of a goat emerging from its back. The serinan species is, of course, only vaguely alike. The chimera, descended from the sprinter subjugator, most clearly shares in common the "snake tail" trait, for it has evolved an extensible membrane near the end of the claw-tipped tail that resembles the hood of a cobra and contains two large black eye spots, using it for visual communication with others of its species. Chimeras, like other sawjaws, are well-inclined to lash out at prey with their tails, hooking it with the sharply recurved talons, and in this way, it can appear so swift and fierce as to be attacking under its own will, as if a second head, as the animal also lunges with the deadly jaws from its other end. Chimeras do not really resemble lions - the maned manticores are a much better match - but they do fulfill a similar niche on the now vast, seasonal grasslands of the dry, cooling world. Hunting abundant but highly migratory herd animals in small packs, these subjugators have survived the extinction of most gantuans that their ancestors fed upon remarkably well, by switching entirely to a diet of smaller prey species. Crested thorngrazers are the bulk of its diet; its choice of prey is small and easily killed if caught, but is extremely fast, so that the chimera's primary method of hunting is to have greater endurance and wear out the oldest and weakest, snatching them from the edges of the herds as they fall exhausted. Chimeras find distant prey by scent - their nostrils have become one singular open hole to best detect scents coming from any angle, but this orifice can be closed if necessary with a lip-like muscular flap to keep out the cold.

Chimeras live in pairs, sometimes in related packs of up to six if prey allows it, but groups are aggressive to unfamiliar packs, so much so that the most common cause of death is being killed in conflict by others of their own species. Fighting is frequent because chimeras cannot really settle and claim territories of their own - their prey animals are always on the move, following rainfall, and where they go is not predictable month to month or even year to year. To survive all chimeras must trail the great herds, constantly coming into contact with others, and fighting over every scrap. Larger groups win against pairs in fights, but require much more food to survive, and as such, both large and small groups have their own positives and negatives, and so both forms of social living persist. Larger clans do not produce more offspring, because in any size family unit only one dominant female will bear a single pup. But the pup's survival odds are higher with more members in its pack, as not only can they provide more food, but they can also alternate caring for it while other members hunt. Sitting on the back of an adult, a young chimera can easily resemble a second head coming off the adults' back - another allusion to its common name and mythological counterpart.

~~~

For most hunters, all the tools they need to do their job come with their bodies. But some hunters are made, not born. The eaglance is an extraordinary predatory bird known for its specialization toward tool use. A larger descendant species from the upland impaler, life on the firmament pre-adapted its ancestors toward the cool, dry world that was to come at the end of the hothouse. The eaglance, a bird standing 6.5 feet high and weighing 250 pounds, has left the firmament as it become uninhabitable, and is now an apex predator of the vast continental steppe.

Eaglances are nearly obligate tool users; they do not hunt without them unless they are extremely pressed. And the tools they create are more complex than the simplistic spears used by other bonebower for millions of years. Eaglances are extremely smart animals, particularly in regard to problem solving. They are now well into the stone age, and have adapted their spears to feature chiseled spearheads made from flint, improving their lethality and durability. Eaglances use spearing tools innately, but these improvements to their craft are learned and passed down culturally. The need for refined tool making has produced noticeable changes in the eaglance's anatomy. In addition to a permanently notched bill inherited from the impaler, this species has now developed markedly improved manual dexterity, with an elongated, flexible, independent thumb which can be pressed against a rough skin pad on the wrist (present in most sparrowgulls and originally adapted to carry their eggs.) Among sparrowgulls, only the horstrich has a similarly dexterous hand.  Like that species, the eaglance has no capacity of flight, but retains long and very mobile arms, for it uses its hands to manipulate objects in ways very few birds outside the skuorc lineage are capable, and with some help from the bill, it can even tie knots using natural fibers in order to attach long spears made from cane grasses to their spear tips.

The most remarkable tool use demonstrated by the eaglance, though, is likely the innovation of a spear-thrower, or atlatl. Probably the most complex example of animal tool use by a non-sophont animal - and indeed, so complex as to make it difficult to tell just what exactly defines a sophont animal - many but not all eaglances carry these tools, most of which are made by carving the bill casques of a common prey, capricox giraffowl. The crest shapes of several species are broadly suitable in shape to support a spear, and to provide greatly increased leverage when throwing it, so as to vastly improve hunting success for whichever genius individual originally gave it a try. A few species' head crests are functional for this purpose entirely unmodified, but always trying to improve their craft, eaglances generally modify them to the most efficient shape by chipping away at the tines with stone knives and their own bills. Eaglances throw their spears to the side, as they cannot hold the tool in a forward direction, and learning to do so with an atlatl is a complex skill that takes several years to perfect - pairs thus care for a single offspring for many years at a time, and so have a low reproductive rate. The neck of the eaglance is more robust than the impaler, better adapted to endure these high-stress, repetitive motions. The innovation of the atlatl gives this predator an incredible edge over others, for it has developed a long-distance projectile which can reach 100 miles per hour and be used to subdue prey animals more than 200 feet away. But this skill comes with costs as yet unknowable to these creatures, which are incredibly skillful crafters, but have not the foresight to understand that they now have the capacity to drive numerous other species into a rapid extinction.

Yet, the eaglance is not wholly without limits. Living in pairs that do not typically cooperate with other pairs, eaglances often steal tools from each other, and observe others at a distance to acquire new skills. Oftentimes this means that their own kind is another rival to worry about, and sometimes eaglances turn their spears against each other, too.

Though the eaglance is a very smart tool-wielder, there is another animal of the flatlands that shows tool use does not absolutely have to correlate with high intelligence. In some cases, it can become a simple and instinctual behavior. And for some animals, that's all they need to get by.

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As we have seen so far, many kinds of animals can still survive in environment of the flatlands even though it is less productive than just five million years before. Summer rains still transform much of the steppe into a verdant green landscape, and so life, most of it already adapted to grassland settings, persists in reasonable abundance given the circumstances. Among the more common lineages are even a few outliers, groups with little diversity but which have managed to hold on throughout the hothouse and now into the final stretch - groups such as the antlears.

Centears are one of the last antlear lineages, and the biggest species of this era. They are fairly large, horse-like tribbetheres with elongated skulls and enlarged nasal cavities lined with dust-filtering hairs. Their jaws are still typical of circuagodonts, being blade-like shears suited equally to crop low woody brush or, if the head is angled to one side, to quickly clip even very coarse, hard grass stalks. Durable and able to subsist on very poor foods, they have become somewhat convergent upon early thorngrazers at a time where that group is now only survived by two very different lineages, one very short and armored, most of the others resembling ungulates and now unable to survive on such poor quality food (some even being carnivorous.) But thorngrazers the centear is not - its huge antlers are an unmistakable key to its identity. Very mobile, these herd-dwelling grazers raise and lower them in long-distance codes of communication, as well as use them to defend themselves from certain enemies. Yet though these appendages look fierce, the three claws at the tip are not nearly as sharp they appear; like those of the far earlier woodcrafters, they are flexible and covered in a thick skin. They are manipulators more than weapons, useful to pull down the branches of rare steppe trees to strip the leaves, or to lift up their young to carry them from danger - but the centear can also use them to hold weapons.

The centear is overall an unintelligent species. It lacks the drive or the capacity to innovate, to experiment with new behaviors on purpose. Yet it is an innate tool user, albeit one with no ability to make a tool. Much like how a bird instinctively makes a nest, centears instinctively pick up heavy objects and carry them around. They use pieces of wood, bones, rocks, and even clods of soil as extensions of themselves to fend off enemies, throwing or beating with these objects, and so are very formidable animals to attempt to hunt. The origins of these object-handling behaviors may originate with nest-building tendencies in earlier, smaller ancestors. An animal surprised by a predator while holding a nest material could have an advantage in self defense over an unarmed animal, and so over many millions of years those more likely to hold and carry objects became commonplace in the population. Even now, though even newborn centears will carry sticks and anything else they find of interest, they don't naturally know to use them for anything. This is learned, but it is not taught by their parents, nor is it learned through intentional experimentation. A young centear learns through chance; anything which it randomly does and finds results in a favorable outcome it will repeat, even without understanding why it has worked. Much of this trial and error learning process occurs in play with other adolescents, which engage in "games" of hitting each other with sticks and rocks until one of them wins and the other retreats back to its mother - the winner learns what to do with its tools to fend off a foe, and the loser learns that whatever it did was not good, and to try something else next time. It is far less efficient than the investigative play of more clever species, but the centear is working with a small brain and a very low-energy diet. It is usually enough that by adulthood, most centears are capable of using their tools effectively, though as many as one in five never quite figure it out. The brightest minds of all, however, will even learn that tool use can be done offensively too, allowing them to open up very rare and highly nutritious meaty food sources such as armored animal prey. This is such a beneficial skill to learn that there is a great selective pressure to adopt it, and yet it remains rare. Unable to learn from imitating others, hunting with weapons may simply be too complex a skill for most centears ever to figure out.