The Polar Basin

In the hothouse, 290 million years PE, Serina's north pole is a large freshwater ocean, left behind by glacial meltwater filling deep ruts in the ground left by the slow movement of the ice caps over millions of years. Despite its great age, the basin has remained freshwater, for though rivers bring sediments and minerals into it constantly, it periodically overflows its boundaries into the surrounding landscape, a vast matrix of swamps and wetlands known as the upperglades, and so is partially drained and refreshed, never getting the chance to accumulate salinity. Myriad remarkable and specialized life now lives in this immense water system at the top of the world. During the summer, stretches of of the sea become carpeted in just a few weeks by thick mats of floating vegetation, thick enough in some places to stand on, and it is for this picturesque visual that the basin is best known. Yet in winter, the sun dips  below the horizon for months on end, and all this plant matter dies off, surviving as dormant buds and seeds that endure months of total darkness.

Dozens of large rivers drain into the polar basin, which is just over 1,200 feet deep at its greatest depths, and so many of the animals which can do, like the waterhorse - a grazing dolfinch - so will migrate into and out of this sea seasonally to avoid the long-dark winter as their food supply dwindles. Even more fliers come and go with the sunlight, flocks of many species of pteese and handstander tribbats sometimes darkening the skies as they come north to nest and then return to southern latitudes with their young in the fall. These in turn are hunted by enemies such the boltbills - fierce, pack-hunting skewers. River inlets circulate the water near surface, breaking apart the vegetation into many large islands closer to shore. These are kept clear of greenery by the largest herbivores, arctic seahorses - tribbetheres each as big as a school bus. Gantuans are represented by the amphibious snippo, a gigantic swan-like animal that is small enough to move within the thicker mats of vegetation, reaching for submerged leaves with its serpentine neck. Skulossi are present too - relatives of gantuans, but generally shorter-necked, here the bad-tempered greater skuggernaut can be found skulking along the shallow shores of the basin.

Vast fish shoals in this inland sea support many predators; they range from the relatively docile, inquisitive carmine whiskerwhale to its distant cousin, the vicious, sharp-toothed darkshark, apex predator of the underwater realm and a capable predator of even the megafauna of the basin. Some hunters can move on land and water; arctic snagglejaws are the biggest of all foxtrotters, and skillfully dive below water to snag and haul-out dolfinch prey. Despite their frightening toothy gapes and great strength, they are social and easy-going among themselves, and do not hunt on land.

Plants are the powerhouses of this remarkable biome. Taking advantage of the summer's nonstop sunlight, they can explode into growth seasonally and produce an enormous amount of food for aquatic and semi-aquatic grazing animals that range in size from fairly small to outright colossal. 

The largest animal of the polar basin is also one of the most alien things Serina's biosphere has ever produced: the gigantic, superficially four-eyed arctic sea horse, an herbivore descended from the tribbocampus that is among just two large herbivores that don't leave this inland sea in the autumn to escape the long dark winter. A giant which is restricted by its bulk to open stretches of water where currents keep floating vegetation parted, it reaches a length of around 40 feet, weighing as much as 40,000 pounds, though this weight fluctuates drastically through the year. It is, unequivocally, the biggest tribbet that has ever lived and has become even larger than oceanic relatives because of the extremely abundant food available through the summer, and then a need to defend itself from large marine predators through the winter. 

Sea horses are all distinctive for their eyes, which are divided into two sections - this is responsible for the translation of the genus of the arctic sea horse, "four eyes", though there are actually only two very specialized eyes. A strip of skin tissue overgrows the middle of the lens, splitting them into two surfaces; each blinks independently and is only covered by one corresponding eye lid. This trait arose in the tribbocampus to let that animal see clearly above and below water at the same time; now each eye now has two fully divided pupils which can be focused in different directions, and two corneas. The brain of the sea horse receives four separate visual inputs that it puts together as a composite, allowing it to look in four directions at one time. With its eyes wide and bulging, the lower pupils always point downward and behind the animal, giving it excellent awareness of predators, while the upper pupils face forward and above, letting it forage for food while keeping an eye on danger. Both eyes work well underwater, but the upper eye is also acute for sight in air, as these animals mostly eat floating vegetation and so rest with their eyes - as well as their snorkel-shaped ears - just above the water's surface. Algae readily encrusts the thick hide of the sea horse in the summer months, sometimes forming a flowing green mane along its back that lends some resemblance to an Earth horse.

Arctic sea horses feed around the clock through the sunlit summer months, sometimes eating over 1,500 pounds of food a day and packing on fat so that they can survive the winter when the plants die out, and they must spend several months starving with only their reserves to sustain them, as they are far too big to leave the basin down its connecting rivers as other animals do. From summer to winter, a sea horse's weight may swing from a corpulent 40,000 lbs down to a thin 25,000 or even less. To endure the winter, they gather in vast herds in shallow water for protection from aquatic predators that hunt from the depths below. In winter, activity is reduced and the animals spend almost all of their time resting on the surface, clustered in formations so that their heads - which are armed with bony club-like extensions of the cheek bones to batter enemies - face out, and their fluked tails collectively serve to block the vulnerable calves from attack from beneath, keeping them at the surface and behind all of the adults. Calves, too little to fast all winter, are fed by both their mothers and other related adults in their herds with via regurgitation with a nutritious stomach secretion produced by the adults metabolizing their body fat during fasting, in a manner convergent with the distantly related marine molodonts of the Mid-Ultimocene such as the bonebreaker. 

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Far smaller than the arctic sea horse, and yet perhaps even more conspicuous among the basin grazers is the snippo. A gantuan descended from the soggobbler, this skuorc is one of the smallest at under 30 feet in total length, tail tip to beak. Though all members of this group share physical similarities, the snippo is not a cygnosaur, belonging to its own monotypic genus which has descended without other close relatives for the last 8.5 million years. Snippos represent the venture of the wetlands-associated soggobbler further into the waters of its habitat, while cygnosaur ancestors became more fully terrestrial, uplands browsers. It is now highly adapted to live in water with large webbed hind feet, a paddle-shaped tail, and reduced forelimbs that serve little role in the water and only are used for occasional, brief forays over dry land to move from one body of water to the next. Notably dimorphic, the female snippo is mostly grey with faint barring, but the male is extraordinarily colorful, and is banded with vibrant patterns of black, yellow, green, red and gold. Males have higher tail flukes, decorated with stripes, and used in display as well as a large fleshy dewlap and red knob on the bill. A harem species, males fight over breeding rights with female herds.  He is not an animal that tries to hide - he wants to be seen, from far and wide, his colorful patterns a signal of his fitness.

Snippos are small enough, with narrow bodies, to move through the floating vegetation that larger animals cannot. This lets them reach the best grazing, and provides some cover against large predators. Newborn snippos, though, are not strong swimmers at all - they are long-legged and more terrestrial than the adults, and don't live within the basin itself. They somewhat resemble the chicks of cygnosaurs, but are bipedal and well-adapted to run on their hind legs. They live first in the wetlands of the outlying upperglades where they catch small invertebrates, and become both more aquatic and more herbivorous over their first two years of life. Adults, when they walk over land, are quadrupeds due to the fact that their body continues growing after their legs stop, but can rear up for short periods to look around their surroundings.

Like the cygnosaurs, the adult snippo is mainly an herbivore, but also consumes animal prey in the form of small fish and invertebrates. It feeds by dipping its long neck below the water's surface to grab seaweed but rarely dives, preferring to tip its tail up and dabble from the surface, reaching plants up to eleven feet underwater, as well as to graze grass and browse low trees along the edge of rivers.

Widespread over northern serinarcta, the snippo is common in the polar basin ecosystem but not restricted to it; it is a summer visitor, migrating south in the fall to avoid the dark winter, and where present it is limited to near-shore waters. Its main predator here is the fearsome darkshark, which restricts its presence in the basin to the weedy shallows. The undisputed apex predator of the basin, this powerful whiskerwhale is also the most significant threat to the arctic sea horse.

Skuorcs - in the form of the whiskerwhales - have become a major marine tetrapod lineage in the latehouse, and a unique one, for they use their tails to propel themselves instead of the flippers and feet of almost all other aquatic birds contemporary and extinct (eargills, a distant relative, being the major exception.) Though the more aquatic squotters - which had already begun to evolve fluked tails before the end of the ice age - died out in the rapid warming event, their living relatives fell back into their roles almost immediately afterwards. Now they swim worldwide waters, with not only strongly-forked, horizontally-moving tail fins but stabilizing dorsal fins. Like dolphins, icthyosaurs and sharks before them in the tree of life, whiskerwhales have adopted a streamlined, fish-like bodyplan that makes them swift and agile swimmers. Their jaws are long and lined with sharp tooth-like keratin projections, like the beak of a merganser duck or a penguin (and precursor to the teeth of dolfinches,) and used for the same purpose to grab struggling piscine prey. The eyes of these hunters are large and in some cases appear massive, well-adapted to pick up the faintest traces of light in deep waters where most species find their food, diving many thousands of feet below the surface to depths where sunlight may no longer shine at all. Even when the environment becomes pitch black, and the light is gone, they can still hunt effectively by relying on another sense to navigate, using a new integument to do so.

Whiskerwhales are mostly without scales, though some small scutes may still be present near the jaws of some species, where they provide protection from biting animals or from the rocky sediment as these creatures forage for food on the sea floor. Their bodies are smooth and featherless, but they are not bald entirely. Specialized bristles have evolved along the faces of all species, each one connected to a small muscle in the skin and to a nerve. The muscle lets each one be moved independently forward and back, so that they can be extended to feel ahead of the jaws while foraging and pressed back against the face when swimming to reduce drag. The nerve means each bristle extends its owner's reach of touch substantially around its face, letting it navigate near the sea floor without hitting obstacles and also sensing minute vibrations in the water that give away the movements of fish nearby. These bristles aren't feathers but rather a new structure evolved from its facial scales that develops more like the fur of a tribbethere - a simple strand of keratin, stiff and quill-like, and their entire use is to heighten the animals' sense of touch.

Usually, whiskerwhales are marine, but the vast size of the polar basin has allowed some of them to make an exception and become freshwater dwellers. Riverine whiskerwhales, which live in the shallow and complex environments of the basin's vegetated waterways where beaching one's self is a very real possibility, have evolved addtional whiskers along their bellies and down a line from their necks all the way to the tips of their tails. These hairs detect the direction water is flowing at all times and let the animal immediately evaluate the diameter and depth of shallow creeks before finding itself stuck in water too shallow to move freely in. Carmine whiskerwhales, which spend their adulthood in the polar basin and adjacent lakes, can freely dive to the dark, sunless depths of this inland ocean in search of prey and use their extensive touch sensitivity to find and pursue their food in total darkness and cramped, dangerous conditions in caves and rocky crevices near the bottom of the sea. 

The carmine whiskerwhale is also noteworthy for its remarkable color - bright, crimson red over the front of the mature male. Males use their colors to stand out to females during the autumn mating season as they jump out of the water and display their fitness and suitability as a mate. Yet the low energy waves of red light are the first to disappear underwater, rendering the hunter black and nearly invisible in the shaded depths as it hunts; the striking color becomes indistinct in as little as six feet of muddy water.

Unlike many skuorcs, carmine whiskerwhales care for their young. They travel upriver to give birth in calm, shallow, and relatively safe nursery ponds. The young are born in small litters of three or four and are precocious and able to hunt immediately, but rely on their mother for protection from predators for the first three months. After this time their mother departs, often having lost weight and needing to feed in deeper waters to replenish lost reserves. The the fully independent juveniles spend two to four years in shallow, warm riverine and marsh habitats before instinct tells them to head downriver and return north to the basin where they will spend the rest of their lives once they are less vulnerable to its larger aquatic predators - first and foremost, a larger, much fiercer distant cousin.

The darkshark is an apex predator of Serina's polar basin in the late hothouse, a pelagic sharkittty whiskerwhale that grows to a length of up to 15 feet. Closely related to the oceanic black snipper, the darkshark is a rare example of an oceanic whiskerwhale living in freshwater. While riverine whiskerwhales are common here, and better adapted to navigate shallows with whiskers all down their length and more flexible bodies, darksharks descend from the chance wandering of early sharkitties like the snipper. Its ancestors probably reached the basin by swimming upriver for hundred of miles, likely by accident, as little as two million years ago. Once there the species grew greatly in size to take advantage of the seasonal abundance of prey it found in the isolated inland sea during the summer. Now too large to leave the basin and its associated waterways and return to the ocean, darksharks are stuck there year-round and must endure the dark winter when the migrating herbivores such as waterhorses and snippos have left. 

The darkshark lives in two worlds with the changing seasons. In winter it is solitary, diving thousands of feet deep, to seek out the basin's large freshwater fish. Its eyes are huge and round with wide pupils in low light conditions, each bigger than grapefruits, and give it a cute appearance despite its great size and formidable nature. With them it can detect and make use of even the slightest trace of light in deep water conditions no human could see in, but in the depths of winter nothing reaches these depths, and so the darkshark relies on its many long and highly attuned whiskers to locate the slight vibrations of fish swimming nearby. It has keen hearing too, which can detect the clicking and popping noises produced by certain fish as they communicate amongst each other with their swim bladders.  Occasionally it preys upon its distant relative the carmine whiskerwhale, as well as other relatives that don't leave the basin in the fall.

Come spring, the darkshark changes its behavior and begins to spend more time near the surface. It also adopts a change of color, its skin becoming lighter and dappled with tan streaks that help obscure its shape from above. Wide eyes recede to sinister slits in the sun, and the darkshark becomes a deadly ambush predator. Throughout the summer it feeds mostly on visiting large herbivores, taking them by surprise in vegetated water. Its jaws are lined with serrated triangular teeth like a shark's, and its jaws open wide to get a grip on prey bigger than itself and leave devastating wounds. At this time as the population becomes concentrated near the herds, it hunts in loose packs which find benefit in targeting prey together and helping one another isolate targets from their groups. They attack suddenly and with great ferocity in packs of five or more, churning the water red and spinning in death rolls to tear chunks of flesh from the hapless victim that can do little to defend itself. Feeding frenzies result in which every darkshark around gathers around the commotion and then begins trying to snap up as much meat as it can, often missing the mark and grazing each other with their teeth. This leaves most specimens marked with jagged white scars over time, which heal quickly and are only a superficial blemish.

Darksharks can, at times, threaten nearly anything living in the basin. But they are not the primary enemy of all the aquatic herbivores. Some are simply too well-defended to regularly take down. One such example is the bloop - a massive, fully aquatic trunko descended from the shucklump. It swims along near the surface, propelled with kicks from its flipper-like feet and steering with the mobile fin-shaped upper flanges below its eyes, each of which is armed with a folding switchblade-like spine used to stab predators like the darkshark that attempt to go for a bite at its head. The flanges of the bloop and its close relatives are the most derived of all the sealumps, with skeletal elements lending strength and cartilage joints connecting them to the bones of the skull giving them a wide range of movement. The four flanges, which evolved in the first sealumps as flexible lips to help pick up food, have here become additional facial limbs in their own right, joining the small trunk in letting these trunkos navigate their environment and manipulate food with exceptional ease.  

Yet, the bloop is not an aggressive hunter itself, and though it aggressively defends against its enemies, its diet is made up of far, far smaller creatures. Nonstop daylight atop a deep, highly circulated body of water with upwellings of benthic sediments results in a massive flush of seasonal plant life. The very first photosynthetic organisms to appear after the dark, when the sun is just beginning to shine over the horizon, is floating single-celled green algae that turn the surface waters green almost overnight. It takes advantage of the delay higher plants have in taking advantage of the first morning light, for as they must assemble bodies for themselves with stems, roots, and leaves, this algae can simply multiply cell by cell at an extreme pace to make full use of it before competitors appear and it is out-competed for resources. These algae feed tiny microrganisms and zooplankton, such as insects and the larvae of fishes, but they are too small for most large vertebrate animals to graze on as they do the higher plants. The bloop is an exception.

The bloop has evolved an incredible facial structure from its flanges, the first pair now shaped like nets and lined with thousands of bristles that serve to sieve this algae and the small animals that feed upon it from the water in mass quantity.  For half the year they gorge on the flush of plants, starting with the green water of the spring and then transitioning to the thick clumps of algae and floating plants of the summer, all swept into their wide mouths with in and out pulsations of their huge flanges that pull in mouthfuls of anything around them, not just plants but all the small fishes and invertebrates hiding within them.

Bloops are named for their short, low-pitched calls which pulse through the water as individuals keep in touch with their herds. They are extremely gregarious and rely on group organization to fend against predators - though at up to 10,000 pounds and 25 feet long, they are bigger than any which coexist here by a wide margin. The bloop is the basin's second-biggest full-time resident animal after the arctic sea horse - but it's a distant second - and it is also too large to leave the basin by route of river in the fall. As the basin turns brown in the autumn and the plants die back, the bloops - now up to 1/4 heavier than in spring from their gluttonous summer feasting and carrying thick deposits of fat - transition to a carnivorous diet of crustaceans and small fishes that come up from the depths to spawn in the arctic night. This food source is irregular, but high in calories, and the bloops get through the dark times by feasting and fasting in equal measure as the prey populations near the surface rise and fall. Too buoyant to dive far, they are slow swimmers. They don't run from predators but turn to face them as one, stabbing them with their flange-spike and kicking out with sharp clawed hind legs to defend their chicks from enemies in the shadows. Their vision is good, especially in low light, but their sense of touch is even better. Every bristle in their nets connects to a nerve, and together form feeling organs sensitive enough to detect the tiny movements in the water that indicate a predator at a distance way before they could see. The vibrations produced by animals like darksharks, with fast-flicking side to side tails, are distinct from those made by their own kind and allow the herd to assemble in defensive organization well before the hunter can strike. 

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In another polar basin animal, an even more heightened sensitivity to movement in the water allows a smaller animal to locate not enemies, but food sources, in total darkness. The ness, a very strange dolfinch, dwells far away from most of the basin's birds and tribbets, finding its food in the depths of the murky water where sunlight is absent not just in winter, but all year long. In the deepest, darkest waters of the polar basin, monsters lurk. Their presence on the surface is nearly nothing: a ripple that might have been a fish, or a small splash... just a solitary wave? Rarely, a pointed beak pokes up for just a fraction of a second. A breath of air. And again, it is gone.

The ness is probably the weirdest dolfinch that has ever or will ever live. 20 feet long, more than 3/5ths of its length is made up of a stiff rod-like neck - an extraordinary outlier in its group, most of which have short, compact necks. This animal is a descendant of the ploose which has grown to an incredible size in this special place unlike anywhere else on Serina now or before. It is found in several large river systems in northern Serinarcta, but its distribution is centered upon the inland freshwater sea in the polar circle where its ancestors have lived for over 10 million years. Here it forages in dark, murky waters for small fish that it surprises from afar with its neck, which is so long as to obscure the body behind it, and then snatches in its long serrated beak. Unlike many modern dolfinches, this one is a predator. It dives to depths of up to 1,200 feet - the very deepest recesses of the sea - to hunt its quarry, holding its breath for more than 100 minutes at a time. It stores a supply of air in its incredible neck to help it endure long periods away from the surface, like a diver's oxygen tank - and to compensate must consume stones for ballast to help reduce its buoyancy.

Ness hunt in places without enough light to see by. Whether deep underwater or in the mud-choked depths of rivers, vision is all but useless to find food in its choice of habitat. So over time these birds have lost their eyes altogether - not even a remnant remains visible in the adult, though chicks are born with small eyes faintly visible below their skin, which become buried in muscle tissue as adults. They don't need to see their food to catch it, for they can utilize a special sixth sense in the form of electrosensitivity. The sensitive beak of the ness's platyporp ancestors already held the first hallmarks of this new ability and helped it to locate small animal prey hiding in muddy sediments. Ness have hypertrophied this sense, their beaks being covered in highly sensitive tissue pitted with hundreds of thousands of electricity-sensitive pores. Using a side-to-side motion of their heads, ness gauge the direction and distance of their prey by registering the electric charges its muscles make as it swims. Without eyes, the visual center of its brain now controls these new sensory inputs; in its own way, the ness may literally see in waves of electricity, even in a world without light.

 But the ness is not limited to passively sensing electricity produced by the movements of other animals. Its immense neck is able to generate a weak electric field, with an electric organ originating from its syrinx - its vocalization organ - that vibrates to produce a weak electrical charge. It is probable that these now-specialized  muscles' production of small amounts of usable electricity first originated from vibrations that  the organ produced during echolocation calls, and that electrosensitivity later usurped this method of finding food by being more effective. By projecting electric fields around itself from pits running down its neck as it forages, it has even finer sensitivity to detect anomalies produced by the muscle movements of other animals close by. 

Ness are social; pair bonds are the primary social structure, with mated couples cooperating to herd and capture fish. Though communication between pairs is primarily vocal in the form of high-pitched whistles, there is some degree of electrical communication. To avoid jamming each other's signals, for example, pairs in close proximity release electrical pulses at different speeds so as not to overlap. These specific frequencies soon become signatures consistent to each partner, and so instantly recognizable to one another versus strange ness or other types of animals in the environment.

Ness may be without eyes, but they can detect light with the pineal gland on the back of their heads. In this way they can track seasonal changes as they come to the surface to breathe. In winter, when the sea is dark throughout the day, they follow the deep water fish into the surface waters and can forage in much shallower levels than they do in summer. They give birth in winter to 2-3 relatively large chicks, which both parents tend to and provide food for until they become more capable. As very young ones cannot dive like their parents, a winter birthing season allow their chicks to hide in the shallows, cloaked beneath the safety of the polar night.

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Another animal that can only be seen in the shallows of the polar basin in winter is the springler is a common but rarely observed sawjaw widespread across the upperglades. Standing only twelve inches tall and weighing four pounds, this is one of the smallest sawjaw species, though relative to its body length, it has one of the longest tails of any - over 1.5 times the length of the rest of the body, which they use to catch prey. Descended from the springheel, it is just one of many descendant lineages of that species which have evolved to survive in many different habitats in northern Serinarcta in the late hothouse. Allied by their hopping locomotion, most of them are quite small, and though they evolved in plains, most are now animals of thickly vegetated habitats. Some climb trees, other stalk forest undergrowth. But the springler is a specialized fisher, a shy, nocturnal hunter known for taking up silent, immobile vigils along the shores of the basin and its tributaries after the sun sets. Many of these solitary, secretive animas live year-round in more southern wetlands, but the thickness of the vegetation makes spotting them far more difficult. Along the basin in winter, they may be seen to emerge onto open beaches - taking advantage of a seasonal lack of their own predators - and they may even gather in loose groups to hunt the fish which come up from the depths when the sun disappears. Waiting patient and unmoving, they suddenly snatch unwary fish out of the water with rapid strikes of their tails when they come within range. It devours its mollyminnow meals with a somewhat atypically long set of jaws that no longer interlock in a sawing motion, making this one of the most derived sawjaws. The mouthparts now operate like a simple beak, holding slippery prey between the two serrated teeth before it is consumed.

Though they do not absolutely depend on them, springlers have exapted the ear tufts of the springheel, used only for display, into a practical and novel organ used to lure fish into striking range. Like their tails, their ears have become immensely long, most of the length being a simple rod of cartilage which is very flexible and whip-like. By lowering one ear at a time and skittering the furry tuft at its end along the surface of the water, it imitates an insect larvae or a small injured fish, and eventually draws the attention of prey which comes to investigate and is promptly captured by the animal's tail. The tail is so long and flexible that it can be suspended up above and ahead of the body, so that it strikes toward the mouth, rather than away. This causes fish to flee further toward shore, rather than into deeper water, and improves its hunting success significantly by giving it a second chance to snatch up fish with its jaws that it missed on the first try with its tail. Occasionally, an over-eager fish might injure the springler's ears and bite off the lure. But tribbetheres have a high capacity for regenerative wound healing, and the tips will regrow within a few weeks. In the interim, the clever springler may make use of alternative lures, sometimes holding a small grass stalk in its mouth to fill the same role. The smartest members of the species will take this simple tool use to a more impressive level, and have the forethought and planning to collect small worms and insects and use them as live bait to draw in an even greater number of their own prey. 

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Most animals of the polar basin live their lives in reverse of the ness and the springler. For them, summer - not winter - is the time to arrive, to have young and to feed. The basin draws immense numbers of migratory birds as spring returns to the north pole and allows plant life to revive and cover the surface of this massive inland ocean. Seraphs, including the descendants of pteese which have in this era filled many of the niches of waterbirds, are among the most numerous. Tens of millions of such birds descend here in the early summer, gathered to feed and to breed on the seasonal abundance. Other animals in turn take advantage of the migration, yet in very different, sometimes unexpected ways. The basin boltbill does so in the most expected way. It hunts them, and is a large skydart that has specialized in taking down large flying birds. With a wingspread of up to 7 feet, it is an imposing figure. Despite its wingspan, however, it is lightly built and weighs only around ten pounds. Wings are as light as they can be, compensating for a head and neck which is exceptionally robust and heavy for a flying bird, as it is adapted to endure great concussive stress. Like their small ancestors, boltbills kill prey by ramming it from above in a dive and skewering its abdomen with their rostrums. Though basin boltbills are slower than their precursor - they reach a maximum speed of "just" 90 miles per hour in a less steep dive - they are also pursuing slower flying prey which can also put up a stronger fight than songbirds. Like ice age skystrikes, whose niche they have effectively taken over in their absence, they are brightly colored with shimmering blue plumage above which serves to reflect sunlight and blend in with the water below, reducing their visibility to even larger hunters, while their underside is stark white and helps make them harder to spot in both sunny and overcast skies.  

This skewer is remarkable for its extremely social nature, and it is an obligate cooperative hunter, which can only feed effectively in a group. As such, social bonds are strongly developed, and the species lives in very stable packs which work as a team to single out, catch, and dismember their prey without ever leaving the air. Intelligent and cunning, a group of hunting basin boltbills often position themselves in a close formation far above their prey, so that they are just below the sun from their prey's perspective, and so rendering them very hard to spot in the glare that reflects from their own feathers. Their eyesight is extremely acute; the pupil can contract to an almost invisible slit to block that same glare, and so they avoid hindering their own vision. The pack singles out a single individual from the edge of a flock, communicating their choice with a series of high-pitched pinging calls that are above the hearing range of their target, and then in an instant the group begins to drop from its "hiding place" in the sunlight and closes around their quarry from all sides. Immensely agile, the boltbills can turn on a dime with their narrow wings and long forked tails, and they can even turn upside down momentarily to get below their prey and prevent it from diving down to safety on the water below. The method of killing their food is different from earlier, smaller skydarts in that no one individual hooks the bird on their beak and carries it; rather, each one stabs it through the abdomen and retracts its bill in short succession, causing rapid debilitation. Just before the dead or dying bird hits the water in free-fall, multiple boltbills hook it through the patagia of its wings and carry it together as the rest of the clan swoop in and rip open the carcass with their radulas and greedily gobble up the flesh, letting the bones fall one by one from the shredded remains until little is left. Those who carried the carcass then let go, letting what little remains drop to the waters below, and fly up close below the others, who regurgitate chunks of their own meals and so feed those who made the whole meal possible in a reciprocal gesture. No fewer than three boltbills can successfully hunt in this way, and most often groups are made of up four to ten.

The larvae of the basin boltbill feed on the refuse of both seabird and tribbfisher nesting colonies, which is where females deposit their clutches of eggs. Though there is no recognition of offspring, juveniles may be fed by any adult which they come across in a remarkably altruistic system of species-wide communal childcare. This is only supplemental, however, as the juveniles are competent hunters of smaller birds themselves and so can find most of their food without this additional assistance; clans will recognize individual juveniles which seem to be spending too much time begging for scraps, and will only feed them occasionally so as to force them to still be self-reliant. Exceptions to this occur during the fall migration, when juveniles join the adults in trekking far south following the migrating birds, during which time the young may be unable to hunt for themselves for several weeks, and so are more heavily reliant on the adult's generosity.  

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Another bird of the polar basin has a very different dependence on the migratory seraphs, for it is tiny - far too little to hunt even their youngest. Further, it cannot fly and has no wings at all. And this is why it needs these far larger birds: as transport. But we will return to that in just a moment.

The seaskipper is a tiny trunko evolved from the sogstepper which makes its home on the arctic basin. One of the tiniest of rhyncheirds, this animal weighs just barely over three ounces, and is barely bigger than the domestic canary it evolved from some 290 million years ago - except for its huge feet. Each toe of the seaskipper is nearly as long as its own body and covered with extensible fringe-like scales that allow it to do the seemingly impossible: run on water. Though it spends most of its time scurrying across floating vegetation across the polar sea, if startled - or to catch an unsuspecting small fish or swimming insect  - the skipper can dart across the top of the water itself so long as it steps quickly enough and with enough force that its wide-splayed toes don't break the surface tension. As long as it doesn't stop running, it can continue this for an indefinite distance, literally skipping across the sea between patches of plant life on which it can rest.

Seaskippers eat a variety of insects and small vertebrates. Many of them are caught in the water and on the surfaces of the floating plants. A fair amount of their diet though comes from a more unexpected source: the pests of other birds. Flocks of millions of large seraphs come to the arctic basin in summer to feed and breed on the temporary boom of plants. In many places, the flocks float on the surface of the sea like islands in their own right. As they rest periodically throughout the day, they tuck their heads in their wings and sit idle on the water in droves, digesting their food for a bit before returning to their foraging. Now the seaskippers come from all around. They make quiet, soothing peeps that the seraphs respond to, and as they spread their wings and fluff their feathers, the skippers hop across their backs, probing their feathers and picking out lice, mites and worms that bother the flocks. The arrangement is of course mutually beneficial, and the seraphs seem to enjoy the attention as the birds work them over, even climbing on top of their head and picking their nostrils. When the time comes for the flocks to disperse and feed again, the seaskippers climb off and return to the vegetation.

This symbiosis with large flying water birds is beneficial in summer for the extra tidbits of food that their parasites can provide. It becomes their lifeline, however, in the winter when the basin grows dark and uninhabitable. They are tiny and flightless, but their summer habitat near the arctic circle is only inviting to them for half the year. When the plants die off in the autumn, the seaskippers have to leave. They could never run the distance twice each year from the productive arctic summer to the soglands hundreds of miles south where they must spend the winter - but if they stayed, the plants they walk upon would die and sink, and they would drown. The seaskipper has found a solution to this predicament in an incredible way: it hitches a ride south on someone who hasn't lost their wings. The toes of the seaskipper are very dexterous and can grip tightly on the feathers of the seraphs. Just as the polar night descends and the plants wither, the seaskippers move in with the flocks full-time, perching in small groups on their backs as they glide over the water. When the last food is gone and the time comes to fly south, the seraphs take their little companions with, clinging tight to the feathers on its shoulders. They carry them down to the soglands, past the reach of the longdark night, and there they go their separate ways for a few more months. Come spring, however, the skippers meet the flocks again and ride them back north. This unusual arrangement suits both parties - the seraphs can always count on being clean, and the seaskipper can make use of the incredible boom of insect prey that emerges in the far north for just a short period each year, which would otherwise be beyond their reach. 

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During summer, one of the most important plants for the survival of the seaskipper is a giant floating clover known as the giant pontoon lily, for its adult life stage provides a vast raft for this small trunko, and other birds, to live far out at sea even though they are not strong swimmers, letting them take advantage of abundant food such as surface-dwelling insect larvae that they could otherwise not access. This plant is notable for its two very different life stages, an adaptation to the dramatically changing seasonal environment. Pontoon lilies live just one single spring and summer season, yet in that time, thanks to the constant daylight, can grow from a seed no larger than a walnut, into a colossus twenty-five feet across and weighing some 500 lbs. They begin their short but impressive lives as seedlings, which take root in the dark of the winter along the shoreline, and there establish a sturdy root system with their energy reserves, so that come first light of spring they are primed and ready to send out long green shoots. These shoots float out onto the water, held aloft by clusters of three hollow, air-filled leaves, each of which grows from a node on the stem which also sends down roots to absorb nutrients and anchor it, if the water is shallow enough. The juvenile plant grows quickly, as much as six inches per day, until it has become a vine as much as 25 feet long and has floated into water too deep to root down into the sediment from the surface.

Now the plant begins to undergo a change. Its terminal bud, from which its vine has grown, dies, and instead its most recently-developed leaves begin to enlarge. Over the next few weeks it stem rots away, and with it its oldest foliage, while one to three of its youngest three-leafed clusters and the single nodes each is attached to break away and become independent, free-living plants of their own. They float out deep into the lake, to places their seeds could never have taken root, by angling their leaves up from the water in the direction of prevailing winds, like sailboats - and now they are used as such by birds such as the seaskipper, which makes its home on the plant and forages for food along and beneath its edges, always drifting to new territory in the wind, and so always floating to new hunting grounds so food is always abundant. In this way they can travel hundreds of miles from shore. Each adult plant has just three leaves for the rest of its life, which continue to grow as long as it lives. Filled with air, they become as large as rafts until the plant is an unsinkable monster big enough to support the full weight of several adult humans. The node sends out a long taproot, lined with hair-like roots that take up nutrients from the water column; this root, which may grow to some 100 feet long, serves to balance the plant upright and prevent it from blowing over in high winds. Once grown it can also serve as an anchor, grasping the sea floor if it blows toward land well before the water is so shallow that the floating part of plant becomes beached. This gives it time to angle itself again so that the winds, as soon as they become favorable again, will push it back out to sea.

Adult giant pontoon lilies appear delicate from above. Their dorsal surface is smooth and semi-transparent, allowing sunlight to enter inside and hit the photosynthetic tissue that lines the interior surface of the balloon-like leaves. Yet from below these plants are armed to the teeth with spikes and thorns up to six inches long which cover the underside of each leaf, while the taproot is lined with irritating barbed hairs, all to deter the sea's abundant aquatic grazers from trying a nibble. Animals nonetheless utilize the huge leaves in other ways, with some taking the smooth tops as resting places, hauling out on top of the rafts, and smaller ones hiding below them in the tangles of spines from larger predators. The spines of the pontoon lily also serve to push away and sink competing water plants as it grows, especially when the lily is still small. In spring the waters of the arctic basin are covered in many smaller floating plants, while the pontoon lily is still in its juvenile growth form near shore, but by midsummer the adult pontoon lilies in some places have grown so large that they cover the water's surface and block out much of the light to other floating plant species.

Adult pontoon lilies spread quickly even after their own leaves are fully-grown, doubling their own body mass every three weeks as they clone themselves. A baby pontoon lily, produced through this vegetative process, is genetically identical to its parent and produced on a runner from its node. Skipping the juvenile life stage, it can become fully grown in as little as four weeks. This clonal reproduction allows pontoon lilies to quickly cover the arctic basin by the end of summer. Yet it does not help them in the event of pathogens or environmental changes if the entire population is effectively one big organism, all with the same genes. So as fall approaches and the days become shorter, the lilies are triggered to flower. Small blossoms are born from the node, which push inside the hollow leaves and there open, protected from water and weather. Small symbiotic pollinator beetles, their larvae being aquatic, emerge just in time to find them, flying out across the sea and honing in on the buds. They chew their way into the leaves, making pencil-eraser sized round holes near the center, and there feed not on nectar but on a portion of the very abundant, very protein-rich pollen that is produced by the blossoms. As they move from flower to flower, the plants are fertilized, and soon set their large seeds. As the longdark winter comes, and the plant begins to die, it can no longer control its movements by the wind. Over the next few months, the dead, but still very bouyant leaves of the pontoon lily are blown back to shore, carrying their seeds with them. There they then decay and drop their seeds in the shallows, where they soon take root, and begin the cycle all over again.

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The pontoon lily's large surface provides nest sites to some types of birds during the summer. The snail-eating skewer is strongly associated with this plant, using it both as a platform on which to make its nest, and a surface on which to hunt its favorite prey. An outlier among daggerbills, this one's diet is composed entirely of only one sort of food: snails, which just so happen to be very common on the leaves of the pontoon lily, where they scrape the algae growing upon it.  

Most daggerbills are known for their fierce looks and violent behavior. These skewers are often large and aggressive, using their lance-like mandibles to stab other birds or tribbetheres and then eating them from the inside out with their tongues. They are usually woodland-dwelling and arboreal, and hunt in the dark, relying on the shadows to let them sneak up on their prey. But the snail-eating skewer is not like most of its family, for it is mostly diurnal, fairly shy, brightly colored, and a specialized eater of molluscs in open, freshwater habitats. 

Snail-eating skewers barely resemble other daggerbills; their beak is short and has no ridged crest nor any prominent fangs. They are long-legged and terrestrial, perching only occasionally, and instead using their long, splayed toes to distribute their body weight while striding across muddy ground and floating vegetation. And they are very colorful, having replaced mottled browns and blacks with a varicolored plumage of red, blue, and green. The colors are all non-iridescent - very rare among birds with blue coloration - because they aren't produced by the refraction of light through structural coloration. Snail-eating skewers are the only birds known which utilize pigment alone to produce blue feathers; it is a unique copper-based pigment related to but not identical to that used by some trunkos to produce green pigments, and is derived from the copper-rich hemocyanin blood in molluscs that they prey upon. Different ways of metabolizing this pigment internally produce all three of the snail-eating skewer's primary feather colors.

Snail-eating skewers, as their name probably implies, are evolved to hunt snails, and this is all that they eat. They do this differently from heavy-billed, mollusc-eating scarreots that crush their food by instead sliding their thin and slightly asymmetrical beak into the opening, prying up the operculum that the snail seals to protect itself, and skewering their prey to pull it away from its shell, while stabilizing the shell with the tongue throughout the extraction process, which takes less than ten seconds. These skewers use several different strategies to catch their prey. In winter and early spring, before the pontoon lilies grow their raft-like leaves in early spring, they wade and catch their food in the mud of the outlying upperglade wetlands, finding it with their toes as they walk near the shore. During summer, the snail-eating skewers migrate north to the polar basin and live on its surface, hunting and roosting on the floating plant life. Here, as they live above much deeper water, they often dive to find their food, propelling themselves with their wings and collecting food in their talons which is carried out of the water and then shucked, with the beak, while on land. They breed when the pontoon lilies are at full size, compensating for a lack of any tree cavities by building their own nests from plant material that are positioned upon these wide floating leaves. In each nest, a single, ravenous, carnivorous larva is raised on an around the clock banquet of fresh snails and pupates just in time to fly south for the winter with its parents, when about 25% their size. The family winters together in the southern upperglades, where the chick stays with the adults until the spring migration and then goes its own way, having learned both necessary migratory routes. It will not breed until its second year of life, spending its second summer growing in its colorful adult plumage, which gradually replaces its mottled brown juvenile feathers.

~~~

There are large animals that migrate out of the basin in the fall, too - it is not a habit limited to flying birds. Waterhorses are plant-eating dolfinches evolved from surfscooters, which typically live their lives in very shallow water where their size - as much as two thousand pounds and sixteen feet in length nose to beak - lets them simply push the plants out of their way as they swim slowly around, often scraping their bellies on the sand as they feed. Such a habitat - weed-choked shallow water -  is hard for fast-swimming pelagic hunters like darksharks to navigate, and so as long as these animals remain there, they are relatively safe from it. They are very comfortable in water that many marine animals would risk beaching themselves in, for though they cannot really walk on land any longer, their four flipper arrangement lets them push themselves along without getting stuck even in water only around three feet deep, and so lets them also leave the basin by traveling upriver. Waterhorses indeed are notable for their migratory nature, making  twice-annual up- and down-river journeys to and from the polar basin, where they summer feeding on freshwater vegetation, and then leave again before the polar winter to winter scattered throughout Serinarcta's large river systems. Some waterhorses travel all the way to the sea-coast and back to the north pole every year, spending the winter foraging on coastal vegetation in areas far enough south to avoid the long period of seasonal darkness. These migrations are dangerous - though waterhorses may be safer than most from marine enemies, now they are hunted en route by shoreline predators. To avoid these foes, the porplets coordinate their migrations to an astonishing degree, with many thousands emptying out from the sea within just a few days to overwhelm potential predators with sheer numbers.

These porplets spend their entire lives in water, almost always at its surface, and rarely in areas much deeper than their own length. They feed continuously, favoring floating plants and those which they can reach from just below the surface with their somewhat elongated necks. They are effective chewers with an efficient grinding motion of the tongue and pseudoteeth in the upper jaw, and can consume hundreds of pounds of greens each day. They are social but not gregarious; small groups mingle and depart, though lasting bonds exist and friends who separate will meet again at a later date. Though they may seem simple-minded and only focused on food, the waterhorse is smarter than it might seem, with a very good capacity for memory of the best routes to take on its travels, which are both taught from older generations and learned by watching others. Waterhorses will also cooperate to help one another when they are in trouble, even aiding totally unrelated individuals - though they appear helpless and rotund, they are still sufficiently large to knock the wind out of their predators, and if a predator gets hold of one it must be quick to drag it onto shore, or its fellows may surround it and pummel it until it lets go. Waterhorses will even help other types of animals escape their own predators for seemingly purely altruistic reasons, including animals that do not closely resemble them or share relations. It is possible this behavior stems from an over-generalization of protective instincts normally reserved for their own small calves, which face threats the adults do not. It is not merely a hatred for all predator animals, for the same types of small carnivores nearby not engaged in predation will usually be ignored.

Male waterhorses display to attract mates in large groups during the fall, shortly before they leave the basin. They raise their necks out of the water and propel themselves up as high as they can get with their flippers in a spyhopping motion, while inflating their throats and a large hollow sac on their foreheads with air to increase their visibility. Females peruse the males, easily able to compare the best-looking of the group with them all next to one another. But this is only half of his job to win her heart. She shows her interest by inviting him to chase her as she weaves and turns and hides in the vegetation. Being bigger than her by as much as 20%, he should be able to catch up to her quickly and so demonstrate his speed and athleticism to escape predators. If he struggles to keep up, she rejects him and goes for another, smaller suitor who may not otherwise have caught her eye. In this way, more males ultimately are able to reproduce in a given season than with most lekking animals, and the species is selected not just for size and strength, but also the ability to better avoid predators. 

Arctic snagglejaws are the waterhorse's arch enemy. Looking like a Spinosaurus crossed with a bear, this species gathers in numbers along shorelines during twilight seasons, positioning themselves along the edges and standing in wait for their prey to come by. These large, polar bear-sized foxtrotters, the biggest of any, are specialized fishers and descend from the finfoot triyena. Now obligately aquatic, even though they still can walk slowly on land, they only hunt in the water, grabbing prey in their huge clawed hands and biting on with long, toothy jaws with a prominent notch to hold tight on squirming aquatic prey. Their fingers and toes are lobed like a grebe's, allowing fast swimming but also not reducing their dexterity to hold onto food, and a large back hump provides muscle attachments for their heavy neck and massive shoulders, allowing them to haul prey up from the water that weighs as much as themselves - a weight that can range up to 2,000 lbs. For more reasons than just its intimidating size, the arctic snagglejaw is one of the Polar Basin's most remarkable animals.

By summer the arctic snagglejaws feed singly, foraging alone along the shores of the polar basin ambushing more widely dispersed prey. But as the seasons change, and the basin's herbivores begin migrate, the snagglejaw gathers in great numbers along the river inlets around the basin and there socialize together. Waterhorses have evolved to migrate all at once to overwhelm their enemies' appetites, with their entire populations coming together and leaving the lake within just ten days time and repeating the process again in the spring. As the hot, wet climate makes saving any meat all but impossible, the snagglejaws gorge themselves. They make the most of the temporary abundance, a sort of celebration, where old relatives reconnect before their lives take them down different paths once again. Males and females breed in the autumn run and females store fat to help nourish their young during pregnancy; they then rely on the spring run to get their newborn offspring off to a strong start.

Snagglejaws are social at all times of year, though, and don't limit their interactions entirely to the seasonal migration of their prey. They evolved from animals with complex, rigid social structures, but have mostly abandoned these rules for a looser, less defined gregariousness; food is not scarce in the polar basin, and it can support a lot of these predators without them conflicting. As each one is so large, they simply hunt most effectively alone, and so they are relatively solitary, not living in organized clans at all. This doesn't mean they are truly solitary, though -  the arctic snagglejaw regularly meets up with others - perhaps relatives, maybe just friends - and enjoy each other's company for durations ranging from a few hours to several days. These meetings are done with intent, and strong social bonds exist; a snagglejaw may travel for several days to where a friend is known to be just to see them, ignoring other snagglejaws it may pass on the way but does not personally know. The strongest of these relationships may be females and their grown young from many years, who keep in touch and occasionally visit her and her younger, still-dependent cubs. Such visitors may bring their relatives gifts of food, and mothers will allow their grown offspring to take their new, younger cubs on outings so that they may have opportunity to rest - even though great distances of time and space may separate them most of the year, these animals never forget their families, and have a great deal of trust in them. This sort of extended family, in which adults leave but return for short visits over many years, is not otherwise well-documented among non-human animals, and suggests the snagglejaw is especially intelligent, even among the standards of its era.

Snagglejaws are complex creatures, and their behavior cannot always be explained by survival instinct. A strong degree of cooperative behavior, food-sharing, and assistance in childcare are common and make sense in the context of animals living together year-round in packs or clans. Snagglejaws spend most of their time alone, and yet they still express these behaviors when they do meet - often to an even greater extent than in more social animals. Sure, there is perhaps some benefit to their genetic lineage to help out as long as their mother is bearing new offspring, for their siblings carry many  of their own genes too. But snagglejaws are very long-lived, reaching 90 years old with some regularity, but females typically stop reproducing thirty years earlier. And yet it is when their mothers (or other close relatives)  are older, and so becoming weaker, that grown offspring spend the most time visiting and helping them. Not only this, but the arctic snagglejaw does not always limit its social interaction to its own relatives, or even its own species. For though it is a carnivore, it is not an aggressive one. It doesn’t appear to take great joy in hunting, and its kills are uncommonly quick and efficient, even though most of its prey poses little danger to itself; mothers are strict with their young and don’t allow them to play with their food, so that this is learned early in life.  Scavengers are tolerated, and occasionally even encouraged if food is especially available, most of all if they are also foxtrotters, smaller species of which may be viewed through a lens like that between humans and dogs; something cute, which they might wish to protect - and snagglejaws are one of a handful of animals that will rarely even adopt other species’ young and raise them successfully, rather than lose interest shortly after. There is little other explanation except that this is truly altruistic behavior with no greater, evolutionary meaning except that it is what the snagglejaw chooses to do.

Snagglejaws engage in other behaviors that seem to have little to do with survival as well - they seem to have an appreciation for beautiful scenery for its own sake. Perhaps it is forunate, then, that this animal finds itself in one of Serina's most beautiful places. Summer brings beautiful days and a tapestry of vibrant green plant life on clear blue water for as far as the eye can see, and as the seasons change, night brings its own wonders. Come winter, snagglejaws may spend many hours staring at the night sky as they see the stars, planet, and swirling aurora borealis above them. For the adults, it is like the return of an old friend. For the young, it is a glimpse into a brand new world, and the sights can captivate them for weeks. Perhaps they just enjoy the color… but this is an animal with the capacity to remember their kin for many, many years even across great distances… is it so hard to believe that they might wonder what else might be out there in a world so vast? And it brings questions to the viewer, too: when and where does an animal become something greater - a sophont? The snagglejaw has no real language, except the simple communication abilities of all social animals, and it has no concept of tool use. It cannot, or does not, alter its environment in any way for its own benefit.  And yet it may be capable of understanding abstract concepts, and it has seemingly well-developed morality, something even sophonts can lack. In the hothouse, the arctic snagglejaw is one of the wisest of animals, and yet its great size and specialized diet are likely to limit it from ever becoming more than it currently is. But to look at this animal in its habitat - a beautiful land, in which it lives in greater peace than nearly any other creature - it doesn’t seem like it would want it any other way. 

For the snagglejaw, just the capacity to appreciate what it has may well be enough to classify it among the higher minds of the animal kingdom. Who is to say the hallmark of intelligence is to want to change that world?

For this one species at least, maybe the polar basin is a world already perfect as it is.