Cold-blooded Killers of the Late Hothouse

The late hothouse climate has made it unnecessary for some animals to retain a warm-blooded metabolism, as the environment is generally consistently warm. Predators in particular tend to lose their endothermy, if they had it at all - it is a very successful life strategy to sit and wait, then ambush passing prey animals, and such a lifestyle does not require a lot of energy. Skuorcs, those generalized tailed quadruped birds descended from ornimorphs, had relatively slow metabolisms to begin with. They have thrived in the global hothouse world 290 million years PE, diversifying into the widest range of forms of any hothouse bird order. Cygnosaurs and skullosi are the biggest of all, but other unrelated lineages exist which have also grown to formidable scale. And unlike even the fiercest gantuans, some are obligate carnivores, eating nothing but other animals.

The skuagators are a genus of huge, almost featherless skuorcs whose protective facial scales have migrated over the entire body, forming a thick and almost impenetrable armor of overlapping keratin scutes. Their only feathers are now limited to very short hair-like plumes between the scales on their bellies, and sharp quills under the throat of males which form some small display function. These scutes provide protection from one another, for these animals are incredibly territorial, but also from their very dangerous prey: skuagators, growing to 25 feet long in the biggest species, now primarily feed on gantuans and their relatives. Widespread, they occur over most of Serinarcta along with their prey, but are always associated with water.

With sluggish metabolisms, these animals have lost the ability to maintain a warm body temperature metabolically because in the current climate it is not necessary. They thus spend much of their time basking on mudflats in the soglands, where they can retreat to water quickly when they eventually need to cool down again. Using the environment to adjust their temperature, they can save energy significantly and afford to eat much less than similarly sized endotherm birds. Yet every so often, every two weeks or so, skuagators do need to find something to eat. They scent the air with one of the best senses of smell in Serina's animal kingdom, scanning the wind for traces of nearby prey with their large tube-like nostrils, the inside tissue of which is heavily folded to maximize surface area. Though they resemble alligators and share an inspired name, skuagators don't lie in ambush for days or weeks in the water and wait for food to come to them. The hothouse is so warm that they can, in short bursts, be just as active as endothermic predators. And when they get hungry, skuagators chase after their food.

They are active land-based hunters, targeting large skuorc prey that cannot run quickly away. With short limbs and a long body, they can hide themselves in tall grass growing along the continent's many rivers, lakes and wetlands, as they slowly approach the herds. When close enough, this hunter charges at a surprising speed, seeking to grab one of the animals alone by surprise as it grazes; if it misses its first lunge, the herd will assemble tightly together, strike out with their tails, or even turn and try to stomp on their attacker as a mob, and targeting one then becomes nearly impossible. Gantuans, even adolescents, are difficult prey; they fight furiously and as they grow they can eventually even smash right through the skuagator's plates, making it imperative that this hunter can only target those which it can physically overpower. The skuagator's primary strategy is to clamp its jaws on the throat of its prey as quickly as it can and lock them tight with a specialized joint, eventually suffocating its prey or causing it to collapse as blood flow is restricted to its brain. Yet this only works quickly if the bite is perfectly placed; often the prey struggles for a long time, and if it escapes the first bite, the skuagator may circle with it, keeping it from fleeing back to its herd, and so battle for hours. Occasionally an additional skuagator may arrive and attempt to take over the kill from the tired original hunter; this is likely to result in the two fighting one another viciously, for skuagators do not share; sometimes the prey may use this opportunity to escape. Smaller prey - thorngrazers, trunkos, and the like - are also hunted, but only opportunistically; they can easily outrun these hunters unless surprised at close range.

A successful kill is dragged into water and guarded by its owner, where it is fed upon for as long as two weeks, even as it becomes thoroughly rotten. Powerful stomach acids digest bone, hair and hide and neutralize most bacteria that would kill other animals, so that skuagators may also consume horrifically decomposed carrion whenever they come across it. Using their size and relatively impermeable armor, these animals readily steal from other predators, only being readily driven away by the largest sawjaws.

Young skuagators are independent from birth, weighing about two pounds and measuring 26 inches long. They are more aquatic than the adult, and hide in water to avoid their own abundant predators until they are several years old. These animals are highly cannibalistic, and their own species are the primary enemies of adolescents; most young will not survive except when an older adult holding nearby territory has died, when one lucky, big young one will eventually take its place by killing all of its siblings and rivals.

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Not all cold-blooded hunters are giants, and not all have had to lose their endothermy. Lumpuses, too, are thriving in the hothouse age. The only surviving non-tribbethere tribbets, these frog-like tripods are cold-blooded by default and relatively inactive, lending them their common name - they often sit around, lump-like, blending in to the environment with drab camouflaging colors. Though toxic species still exist, many have become relatively harmless as their diets have changed and broadened. Some lumpuses now climb trees or tall rocks, and others live in the water, but most plod along the ground, usually at night, and spend the day burrowed into soft soil. Most lumpuses are carnivorous, and while some are active hunters in the warm nights, they more often catch their food by surprise by hiding in this way with just their eyes exposed, leaping on it with toothy jaws as it comes too close.

There are no lumpuses with bigger jaws than the toothtoads. A genus found across tropical Serinarcta 290 million years PE, these creatures have evolved to resemble living bear traps, hiding in the dirt and lunging to bite and kill animals as they stumble upon them. Compared to skuagators, they are puny, but among lumpuses they can reach substantial sizes, much  bigger than their toad-like ancestors. They show strong sexual dimorphism, with males being relatively small and quite mobile while females are enormously fat and nearly immobile as adults. The males of these species weigh no more than two pounds, and move frequently in the dark, scurrying across the soglands to find prey insects, and regularly settling into a new hiding place almost every day. Females, however, are huge and rotund, up to 30  lbs, and rarely move at all. Digging a comfortable hole in which to live, they spend their lives mostly buried in dirt. They are big enough that insects do not suffice; their diet is vertebrates. The tips of their ears have become highly elongated and are twitched above the soil surface as lures, mimicking a small worm, to attract the attention of small predators. Sparrrowgulls, snifflers, foxtrotters, poppits, other lumpuses, are drawn in this way and eaten whole, grabbed by the head and shaken to death; other, bigger animals are grabbed by a leg with an inescapable grip. Prey as big as thorngrazer calves that wander within range incidentally can also be killed by the toothtoad in this way, pulled down and dismembered in their shark-like mouths bite by bite, while bigger animals may have large, bloody chunks cut cleanly from their legs and live to tell the tell with a nasty scar.  A single large meal may sustain the female for more than six months, though she will eat more often - as often as she can -  using excess calories to produce more offspring.

Male toothtoads travel widely in the night not only to find their own smaller food, but also to identify sexually receptive partners. They find them by scenting airborne pheromones released by females in breeding condition, and a spongy crest-like growth around each nostril helps to gather these molecules from the air so the male may detect them. Yet even once he finds a female who has advertised, he must exercise incredible caution - toothtoads are cannibals. His ears are even longer than hers, yet he doesn't use them as lures, but rather feelers. From a safe distance, he approaches where he has scented her to be, and taps softly on the ground. She will then make herself visible, rising slightly from the soil, and he will come closer and gently tickle her back with his appendages until she leans to one side and positions herself to mate. If she does not respond favorably to his massage it means she is hungry, and instead he makes his escape.

Like all tribbets, toothtoads give live birth and nourish their young in utero. Toothtoads meet rarely, so females can store sperm after one mating for up to a year. They have large numbers of offspring in a year due to superfetation; multiple pregnancies, all in different stages, so that she may give birth to one or two small young every week, almost all of the time. The babies are fully independent from birth and run off into the tall grass, being highly mobile and nomadic like the adult male for their first year or two. Females eventually settle down into a comfortable dirt patch, eventually growing much bigger and living far longer than the more vulnerable males. Though they are lucky to live six or seven years, she lives for twenty, and sometimes even thirty. 

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The following text and illustrations were provided by Troll Man! 

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Of course, there are predators around Serinarcta that are much, much bigger than toothtoads. And there are predators even larger than skuagators. With the end of the ice age, the warm climate has had a massive cascading effect on all life on Serina. With the constant precipitation and waterways that riddle the continents, plant life flourishes like never before. With the plant life flourishing for the last 20 million years, the herbivores that feed upon it now grow to immense proportions and numbers. With herbivores in great size and population, the predators too have grown to match them. No prey is larger and more numerous now than the skuorcs, the gantuans and skulossi which tower to dimensions greater than anything that has roamed Serina in previous eras. And so predators have reached scales like none seen before in order to hunt them. Skuagators can only tackle smaller, or partly-grown gantuans and skullosi prey. But there is one cold-blooded killer that can kill even grown giants.

In the swollen waterways of Serinarcta, there is an inland predator more massive than any other, built to dispatch such immense titans in one bite. Longer than a school bus and nearly twice as heavy as an elephant, this is the undisputed ruler of Serinarcta's wetlands. It is the imperious river dragon, a vast, ferocious eelsnake. Jaws up to six feet long contain huge spike-like teeth and a bone-crushing bite, their primary weapon of choice against its preferred prey, the vast multitudes of animals coming down to the shore to drink. A varied diet of such beasts as large trunkos, thorngrazers, skuorcs, giraffowls, and cutthroats, or anything else that moves. Like a crocodile just below the surface, it waits for the regular arrival of the endless herds, easily hidden by just a few inches of murky water above it, despite its gigantic size, and with one lightning strike it snaps up an unfortunate victim. Once clamped tight around its quarry, nothing escapes its jaws. Prey up to to three-hundred kilograms in weight can be swallowed whole after capture, and writhing and coiling its sinuous body allows it to easily tear apart larger animals, especially when working in tandem with other feeding river dragons.

Art by Troll Man 

Although they can reach gargantuan proportions, few actually reach such sizes due to the structure of their social hierarchy and physiology. River dragons live in territorial clans which stake out large swathes of habitable land, defending it viciously and persistently from neighbouring clans. Within these clans there is a dominant breeding pair which actively suppresses the growth of the other clan members through ritualistic biting and aggression, preventing them from ever reaching full size until either the alpha pair dies or the smaller individual leaves for its own territory. This bullying extends down the ranks of a clan, and individuals at the bottom of the pecking order may be only twenty feet in length. This helps keep the river dragons from competing with one another, as the smaller dragons will be limited to smaller prey and their greater underwater agility allows them to capture swimming prey that the larger adults, which specialize in large terrestrial prey, rarely bother with.

The river dragon is semi-aquatic, but not particularly swift on either land or underwater as adults due to their massive size. It travels over land infrequently due to being very slow and vulnerable to attack from terrestrial predators like subjugators. When threatened, it will defend itself from the front with vicious bites, while striking with swipes using its powerful tail from the back; being whacked by a tail able to launch a ten-ton carnivore off the ground can easily cause catastrophic injury. They are comparatively better swimmers, but they prefer shallower water due to being predominantly air-breathers, as they can simply rest at the bottom and lift their head periodically as necessary to replenish their oxygen, and have an inefficient body shape for sustained underwater locomotion. It does often haul out along the shore to bask and allow small birds to pick parasites from out of its skin, however, sometimes several at once.

This preference for shallower water limits their presence from large bodies of water like the Polar Basin and the Centralian Sea to occasional vagrants, which is perfectly fine when they prefer to prey on land animals, although they are also occasionally known to forage along the coast in brackish waters. Murkier waters are also preferred, as it is much easier for them to ambush drinking animals. Juveniles are more wide-ranging, as they tend to disperse far and wide to establish their own territories or join the clans of foreign adults and have a diet heavier in aquatic prey like fish and snarks. Only the very largest, strongest, and oldest cygnosaurs or skullosi may be spared from the jaws of the imperious river dragon, as the gigantic eelsnake is will attempt to topple such huge prey by coiling its body over them to drag them down into the water with its body weight, often helped by others of its clan attacking together at once. The fear of a watery grave is one that dwells within the minds of every thirsty Serinarctan animal.. all thanks to the largest cold-blooded killer of all.

Art by Troll Man 

A pair of sub-adult regal skulossi forage for aquatic vegetation in the shallows along the fringe of a wetland region somewhere in the Central Soglands. Although they travel in large herds, they often disperse over a wide area to forage more solitarily, and these two have ventured away from the shoreline to try and find tasty, nutrient-rich rhizomes in the deeper mud.

In this age, skuorcs dominate the land, and include among their ranks the largest animals that have ever walked Serina. These huge skulossi are nearly fully grown, their adult colouration has fully developed, and they already weigh nearly ten tonnes a piece, but in this golden age of Serinan biodiversity, there still exist predators large enough enough to threaten them. 

This fact is suddenly proven true in a split second, as one wrong step awakens a leviathan lurking in the dark waters; huge, crocodile-like jaws, filled with teeth as big as railroad spikes, spring up with lightning speed to try and snap up the unwary skulossus. This is the undisputed apex predator of the Serinarctan waterways, a river dragon has evolved to gargantuan proportions specifically to hunt the giant skuorcs that now occur in great numbers. With the strength and ferocity to bring down the largest beasts to ever roam the lands, this is a hunter with few equals.