Islands in the Sky

above: a skyland unicorn, Retortunus caelumterrus (sky-land, twisted-together-horn), surveys the world beyond its cliffside home. It dwells on the edge of monolithic monument that dwarfs even the largest land animals ever to live on the world of birds and forms one of the most spectacular environments of the late hothouse.

Spire forests in the late hothouse have adapted to the changing ecology of the world through remarkable means. Survival became most likely if new cementree seedlings were cultivated within range of their parent colonies. In this way, the parent could lend protection and the resources to build a protective spire for years before the new tree was mature and able to extend branches out of its shelter and into the sunlight, far above the height of the mega-browsers. It became rarer for colonies to form on their own independent of their elders due to heavy browsing pressure from both short and tall wildlife in a highly competitive environment meaning most dispersed seedlings died before maturity. 290 MPE, the spire forests remain across Serinarcta, but they have changed appearance dramatically.

These forests now are extraordinary superstructures, immense symbiotic colonies hosting trillions of individual ants and thousands of individual trees, each one genetically distinct from the rest, grown from seed and not clonal division. For millions of years now, many spire forests have remained where they first grew before the evolution of gantuans, spreading up and outwards and becoming immense monolithis structures, the largest organic constructions ever to exist on land. They have built up layer by layer upon the bases constructed by their ancestors, gradually elevating the forests to thousands of feet above the surrounding plain through the gradual deposition of new cement-like material by the ant colonies, and through the formation of soil deposited by bird droppings, dead leaves, and airborne dust caught in their crevices. These formations are functionally a type of mountain, built by plant and animal activity, and can occur as isolated examples only a few tens of feet in width to ridges that extend unbroken for hundreds of miles and reach heights of up to two miles above sea level.

Known as sky islands, these elevated spire forests are also a type of reef, the only one to have ever evolved in a terrestrial, rather than aquatic, setting. Like a reef in the sea, they are much more productive than the surrounding environment. Mowerbirds and other flocking animals which nest and roost on the peaks of the islands deposit incredibly nutrient-rich waste upon the summit that breaks down into a nitrogen-heavy soil which is incredibly fertile. This supports the growth of not only the cementrees, but thousands of species of smaller vines and undergrowth that occur among them, many not found outside this habitat - and these plants provide food and shelter for many other animals. Far beyond the reach of any land browser, these forests grow freely up in the air as high as city skyscrapers, and often lack any adaptations to make themselves less palatable that ground plants may have evolved to defend themselves. For the few animals which can reach them, these mountain glades are a safe, food-rich habitat with fewer competitors or predators than on the ground. This is the home of such mythical creatures as the skyland unicorn, a nimble cliff-climbing thorngrazer descended from the hillhopper, which is notable for the twisted sinus horns of the male that have intertwined into a single crest. Far beyond reach of ground hunters, unicorns cling to these steep cliffs with specialized concave hooves that work like suction cups and dance along nearly vertical rock faces to graze on isolated outcrops of vegetation. Safe from most hunters, they must still beware of giant birds that can fling them from the rocks to the ground below, and from climbing repanthors - an ancient enemy that has followed them from the ground up to new refuges.

Sky Islands are more common in the northern hemisphere, but are widely distributed around the world at 290 MPE, wherever suitable sandy sediments exist for the trees' symbiotic ants to utilize to build the individual spires that eventually form into the rock-like base of the islands. While cementrees can pop up almost any place, as ants can transfer sand grains great distances over time, they reach their largest scale along the southern coasts of Serinarcta where beaches provide an unlimited supply of raw building material. When combined with the cellulose from abundant beach grasses, the hempcrete-like material can be amassed here into immense mountains that form ranges and reach incredible size. These particular sky island formations may be referred to as seawalls. The largest seawalls exist in northern serinarcta, some stretching for over 5,000 miles. But the most biodiverse one is located in south central Serinarcta along the east coast of the Nexal Peninsula, where there is no polar winter. Here can be found the Great Barrier Ridge, which stretches for over 1,000 miles and climbs up into the clouds: its highest pinnacles are over a mile above the sea. It is home to an especially large number of endemic species, though in places is less than thirty miles apart from adjacent seawalls, and so many larger animals which are widespread on other sky islands are also present. 

The seawalls are home to countless animals as well as plants and are extremely productive thanks to seabirds and tribbfishers which nest on their heights, depositing guano onto their cliffs and so transferring nutrients from sea to land. Forests cover their peaks, comprising both ant trees and non-myrmecophyte undergrowth. Different floral communities exist on both sides of the great barrier ridge; its seaward side is home to a sparser assemblage of salt-tolerant plants that cling to sheer rock faces where wind blows away much of the soil, while its sheltered side which is more distant from the water grows a rich tapestry of vines and small trees and forms a more lasting soil layer in crack and crevices. Grazers such as skybex thrive on the more vegetated cliffs facing away from the sea, while hardier creatures live on the more exposed ones that rise against the harsh sea winds. Predators of varied forms stalk both sides of the seawall, too.

Skybex are one of the most common sky island grazers in Serinarcta. These small, nimble thorngrazers evolved from hillhoppers, and now dozens of unique species are defined. The unicorns, though their horn structure is not shared by other genera, are themselves a group of skybex, a broader clade that includes a wide variety of animals in different shapes and sizes, able to evolve quickly in response to changing conditions and isolated habitats they may find themselves in. The larger seawalls provide a greater variety of such habitats along their surfaces, from the beaches below, to the lowest sheer cliffs on the sea-facing edge where salt spray prevents forest growth, to the heavily vegetated upper slopes stunted in size by heavy wind and storms, and finally the lush rainforests that grow on top. Large seawalls influence the weather and can even produce rainshadows on their land-facing edge as they block the movement of evaporated water from the sea, though none are present along the great barrier ridge, for it occurs on one side of a peninsula and rain also comes in from the other direction to wet its other side. Still, a wide variety of ecosystems is present here to support over 9 different species of skybex, four of them not found in any other range. These include the smallest thorngrazers of all, skyraxes, which form a sister group to the skybex and make their homes in small caves on the sheer cliffs. They also feature the tiniest true skybex, the scurrying skybex of the high peaks.

Scurrying skybexes are tiny ungulate-like animals with distinctly splayed toes and soft gripping hooves that let them run up vertical walls by catching traction on the most minute variations in the rocks' surface. They weigh less than ten pounds, and spring from cliff to cliff like a rubber ball, at high speed and yet with flawless accuracy. Lightweight and nimble, the scurrying skybex is less vulnerable to falls than heavier animals can take risks they cannot, bounding gracefully, even playfully over deadly drops. If it does lose its balance, its small size means its terminal velocity is low enough that a fall fatal to anything bigger may not harm this skybex, if it can avoid hitting the rocks and angle itself to drop into a patch of grass or leaves, even if the fall is hundreds of feet.

The scurrier sticks close to the edges of the seawall, but is a creature that lives between two worlds. It spends much of its time climbing up into the crowns of the trees that grow at their pinnacles near the drop-offs, and browsing the leaves they find there, retreating down the trunks and over the edge of the cliff if threatened by terrestrial predators, and in turn racing up and off the edge and into the forest if spotted by flying ones. It lives in groups, sometimes very large ones, as many eyes provide many chances to spot danger before it's too late. Males are brightly colored but not territorial; this is a lek species, like many thorngrazers, and so males display in groups without fighting, allowing females to be in charge of mate selection. Indeed, female scurrying skybex will only be stimulated to breed by a large selection of displaying males. The calls of the males are rapidly rising and falling whistles, produced from the small, forward-curved nasal horns, and the song is accompanied by an energetic back and forth hopping dance. Females seem to be enticed by a sense of danger in a potential mate's performance, and several contenders may be selected to engage in an additional degree of competition by doing their displays on steeper and more risky terrain; the one who shows the best balance and grip, and doesn't slip up, will win her favor.

With no horns at all to speak off - except for their hollow crests - the tiny, demure, and athletic scurrying skybex is one of the least recognizable species compared to its burly and aggressive ice age and early hothouse ancestors. Yet it does have something in common with them, even after so much time. It is highly omnivorous, and eats as many small animals as it does leaves. 50% of the diet on average is meat in some form, and though most of this is insects, it even kills rat-like molodonts and the pups of nesting tribbfishers by stamping down on them with its front legs, as its jaws are comparatively weak. Its stomach is still adapted to make the most of a wide variety of food sources, giving this skybex a competitive edge over other small herbivores with more restricted diets as well as letting it supplement a vegetable diet with more nutritionally dense meals so that males in particular can spend less time grazing and more time attracting mates. Females put their extra calories toward a much higher rate of reproduction than most thorngrazers, giving birth to up to three litters of two small fawns per year.

~~~

Thorngrazers aren't the only herbivores to make a home on the cliffs of the sky islands - they are joined by birds, too. Murds are the only burdles with a cosmopolitan distribution, having crossed the seaway south to north a little over ten million years ago by rafting. Their diversity on the northern continent is less than in Serinaustra,  due to the more aggressively competitive ecosystem and in particular the influences of molodonts which compete for the same food resources and have prevented the evolution of as many large, nutritious seeds as in the south, but they are present. Many of the Serinarctan murds have expanded their typical seed diets to a broader plant diet that includes more leaves and grasses, and some have been pushed to outlying habitats where few other animals were already established to eat those things, places such as cliffs. The steepest upper ledges of these mountains, difficult for larger herbivores to traverse, have become the home of the caprichel, a lanky species of murd that evolved from an ancestor close to the jirdbirds, but now fills a niche somewhere between a mountain goat and a sloth.

The caprichel, once a fairly energetic seed-eater, has here become a slow-moving herbivore that relies on camouflage to avoid detection on its steep territory high on the sky island cliffs. Moving with utmost deliberate motions, it searches for small footholds that it can rest its claws on and frequently climbs with a sideways, horizontal movement with its belly scraping the rock and its back, mottled with a varied grey, brown, and green pebbled skin that closely matches the weather worn and mossy surface of the cement. There aren't many seeds here, so the caprichel eats mostly moss and liverworts that cling to the rocks, scraping off the layers with its blunted beak which grows continuously to compensate for the heavy wear. Moss is not a nutritious source of food, being low in calories, and to conserve energy the caprichel's metabolism has slowed and it is capable only of very short bursts of energy and cannot really run. Its eyes are high on its head and when clinging to the cliff it can see around and above its head, letting it spot enemies at a far distance. It freezes to hide from flying predators - its most common enemies - and can even hold its breath for five or more minutes if being watched; its variegated pattern breaks up its outline, especially in the foggy or low-light conditions when it is most active, and allows it to disappear in plain sight. Yet if it is still seen, the caprichel isn't wholly defenseless. It is too slow to flee, but it can turn and rake attackers savagely with its claws, seeking to gouge out their eyes. In a life or death scenario it will even jump off the cliff, tumbling straight down with its limbs tucked up against itself in a ball-like shape. It may seem delicate, but its bones are solid and extremely robust, and it can survive falls from heights fatal to many similarly sized animals by rolling down the side of the mountain and coming to rest safety in a patch of cliff-side vegetation, out of view.

Caprichels retire to caves or thickets of trees during the midday, emerging at dusk to feed except on very cloudy days where they may be active through the day. Many individuals may share a roost without fighting, going their own separate ways to forage. The only social bonds are between a mother and her young, born in a small litter of three or four, which follow her out onto the cliffs after ten days of sheltering in her den and receive protection for about a month afterwards. Mothers will defend their young by feigning injury to draw predators' attention away from the chicks, then the entire family, starting with the young, will drop down the cliff to escape.

Caprichels are joined on the cliffs by molodont grazers, only very distantly related to the climbing thorngrazers. Known as starrybaras, they are are a family of small molodonts descended from seed-snatchers that have evolved hugely powerful jaws to gnaw burrows through the structure of the reef and there find shelter from enemies. They are most abundant on the seaward side of of coastal seawalls, where the rock is coated in mineral-rich salt spray and from this this animal can acquire large deposits of iron over time which it transfers into its teeth as they grow, lending them increased durability and a bright red appearance. These tribbets feed on the cliff-clinging grasses that manage to keep hold along the wall and especially upon their seeds, mostly emerging to feed after dark. They have evolved an extra-sensitive sense of touch that lets them more easily navigate the steep and dangerous world outside as well as their narrow, dark burrows in the rock thanks to elongated feelers at the tips of their ears - bundles of fleshy tentacles similar to the nose of a star-nosed mole. Made entirely of flexible cartilage, the starrybara swings these fancy ears around to tap everything around and ahead before it steps forward, ensuring it doesn't tumble off a sheer cliff, or squeeze down a tunnel too narrow for its entire body width and get trapped.

But the starrybara isn't invulnerable. Hunters lie in wait along the mountain to catch them as they pop out of their tunnels, and the more dexterous among them try to reach down inside and rip them out. Skyheels - a species of long-snouted springheel that spends its life crawling along the ridge - reach into their tunnels with their talon-tipped tails and try to drag their prey out to kill it in their serrated jaws. Colored brown and grey like the cliffs, they stalk patient and quiet up to a mile over the crashing waves, staking out over the many tunnels dug by the starrybara which mark the cliff in abundance. When they pick up the sound of prey coming near to the edge of the tunnel they freeze motionless and wait for it to come near enough to swing their tail down the tunnel and snatch it. Yet the starrybara is not defenseless - those jaws evolved to chew through cement can easily chew through the bones of a skyheel's tail, and so the hunter must always catch its prey by surprise and pull it out with such speed that it cannot react. Even with the most careful attention, many older skyheels will show signs of injury from prey fighting back, including the loss of one or more claws. 

 Another feared enemy of the smaller alpine herbivores across all the northern sky islands is the superb sky serpent, which can not only reach them in the small crevices in which they may hide by day, but pursue them at high speed as they flee, even between cliffs. A gliding, nearly legless skuorc, it is a species of primitive skuwyrm, and so distantly related to the woozle and other skuzzards which evolved in the earlier hothouse. The Sky Islands, whether or not they abut the sea, are a difficult environment to navigate, filled with sudden drop offs, wide distances to cross, and dangerous cracks, crevices, and loose terrain that can give way, sending an animal tumbling to the ground far below. It is not a surprise, then, that these habitats favor the evolution of gliding capabilities more than perhaps any other biome. By first taking control of their inevitable falls by parachuting with some rudimentary airfoil to slow their descent, animals can then adapt to glide over horizontal distances on purpose, enabling normally grounded creatures to cross gaps between suitable surfaces by taking a shortcut through the air. Most gliders evolve different variations of skin patagium, turning their bodies into fleshy kites to catch the air and ride it from point A to point B, as all animals have skin, and it's an easy way to make a very large airfoil when you have legs to spread out to support it. But what does an animal do if it needs to glide, but has hardly any legs at all? Sky serpents have solved that problem by evolving a flight surface not of skin but of feathers, albeit laid out very differently from their distant flying ancestor birds. These animals are snake-like and elongated, but have not lost any of their legs entirely, having four small but sturdy claws that are used to grip the cliffs and spires of their habitat and give them traction in a steep and difficult to maneuver environment. They move in a way different from most skuwyrms, but utilized by some of their ancestors, with inchworm-like undulation, by pulling the hind claws forward to meet the fore ones and then extended the front of the body forward again, repeating the cycle. 

The heads and bellies of sky serpents are scaly, while their backs support a mane of especially long, sharp feather quills which lay folded tightly backward over their bodies, being longest and most dense at the tail. Initially, the role of such a thick feather coat isn't obvious to an observer, and only seems it would slow down or encumber the serpent as it forages actively for small prey hiding in the crevices of the reef. This venomous hunter doesn't sit and wait for its prey to come by, but seeks it out in its hiding places by squeezing into tight spaces with its extremely thin, flexible body and cornering it, and so not being overly hassled or restricted by its fairly slow manner of moving and its long feather plumage as it might if it had to chase its food down at speed like some of its relatives. And the purpose of all that feathering becomes apparent as soon as the serpent comes to the end of a cliff, or the top of a cementree with no others close enough nearby to reach over to. While other skuwyrms would be forced to make the long descent down and then up again on the other side of a chasm, the sky serpent can pull off a remarkable feat. By leaping into the open air with a push of its tail, it extends the many layers of hair-like feathers along its back into an overlapping airfoil, taking on a roughly oval shape from above or below. Using its tail to steer, it careens at a slight downward angle through the air for up to 75 feet and comes to land on the other side with ease. Once landed, the feathers fold up again out of the way, and the hunter goes along the business of seeking out more food at a comfortable pace, knowing well that its prey can hide, but once it knows where they're at, they can't run. And with its deadly bite to protect it, it fears little from other animals that might try to turn the tables and make it the prey; bold black, yellow, and orange markings advertise the danger that the superb sky serpent poses, and when alarmed it raises its feathers and shakes them to produce a distinctive rattle that says, in no uncertain terms, "I am dangerous." The biggest species, the neurotoxic bite of this four foot long animal also the most virulent, strong enough to kill several men in a few minutes and to dispatch molodont prey in just one or two seconds, preventing these potentially dangerous animals, with their powerful jaws, from injuring their attacker as it comes for them in their hollows. 

~~~

Gliding is such a useful skill to have in the sky islands that it has evolved many times. The spireflyer is a small bumblebadger, a kitten-sized animal that has softer-looking features than most species - including a rounded face, big eyes, and a short beak - due to its smaller dimensions. It is also the most arboreal species. Indeed, this dainty animal, weighing about two pounds, will never touch the ground on purpose. It is adapted well to cling to vertical cementree trunks at the peak of the islands and the cliffs that frame them, with a low-profile body that hugs the surface closely, and a camouflaging blotched tan pattern that lets it perch inconspicuously in the twilight and early night hours when it is is most active.

Don't be fooled - despite its small stature the spireflyer is just as carnivorous as other bumblebadgers, and is an efficient killer, as much if not more than the sky serpent. It emerges from the safety of small crevices in the trees at dusk to hunt other arboreal animals such as molodonts that also scurry along the cliffs. It is a member of savage gravedigger descendants which form a sister group to kittyhawks, the stoatshrikes, which have mostly specialized as burrow-hunting ratters that use their small stature and a collapsible ribcage to slip into narrow tunnels in the earth to hunt prey such as smols. The arboreal spireflyer, though, uses these adaptations to squeeze into holes within the cementrees to reach hiding prey. However the spireflyer has proportionally very long arms compared to other stoatshrikes that hunt on the ground, to the detriment of its ability to chase animals deep into their tunnels in the trees. Using its long, inflexible wrists and sharp talons, it instead goes fishing, hanging in the entrance by its toes, and seeking to pull them out of their holes and then kill them outside, where it has more space to maneuver. It has fast reflexes and can kill animals even heavier than itself by getting a choke hold on their vulnerable throats with the fang-like projection on its beak.

The reason for the spireflyer's long arms is evident when it needs to move from one tree to another. The spire forest is often discontinuous, trees growing up near older trees in clustered pockets, and the next patch may be tens of meters away. To quickly and safely bridge the gap, this gravedigger glides on membranes of skin that extend out from its body to the tips of all four limbs. What these animals lack in flexibility of the arm - which is effectively an immobile rod, as in all bumblets - they make up for with a shoulder joint which can rotate 360 degrees, letting these strange birds spread their wings wide and take flight - or at least, to fall with style, over distances of at least a hundred feet. By climbing to the top of one tree, parachuting to the base of another, and repeating it throughout the night, the spireflyer can cover several miles in its search for prey on a minimum expenditure of energy.

Spireflyers nest in the same tree holes they hunt their prey in, often taking over a nest after killing and eating its original owner. Both male and female cooperatively provide food to the chicks over several months before they begin to make clumsy trips out of the nest to climb on the outside of the spire. The young are dark grey, a color which hides them in the shadow of their nest, but by the time they fledge will be a similar color to the adults. 

~~~

The sky islands are a perfect setting to encourage biodiversity and the speciation of plant and animal life, often being highly isolated from one another much in the same way as islands in the sea. While many animals on water islands cannot easily swim away to another and so the populations upon each begin to diverge in form from one another without mixing, so too do many animals of the sky islands have great difficulty in crossing the miles of open grasslands that divide them. Some long-legged animals like the unicorns or highly mobile species like the sky serpent and the spireflyer make the treks with less difficulty, and so remain a single population over a wide range. But for tiny tree-climbing birds and molodonts, not to mention even less mobile creatures like tree lumpuses, they can find themselves marooned on the high peaks with little hope of ever migrating beyond them, sometimes for millions of years.

Another branch of the skuorc family tree represents the diversity that can form quickly from a single common ancestor in the sky islands in just a short period of time. The chamarmotoos are a single genus of about 50 skuorc species, most of them highly distinct from one another, that descend from a common ancestor living about 5 million years ago. They are extremely arboreal, and in this way have commonalities not only with skuossums but also some skueasels. Their actual closest relatives, however, are the skuzzards (that have some outward similarities) and skuwyrms (that don't), though these lineages split from one another early on, about 16 million years ago. The chamarmotoos have short, sleek feather coats over their heads, torsos, and upper half of the tail, with scaly extremities. The beak has become very short but the mouth wide; they are energetic hunters, spending hours running along narrow vines that they grip with opposable fingers and toes, and catching insects and smaller birds by shoving them down their throats whole with their arms. Wide eyes give good night sight, and a rounded, slightly concave face helps channel noise to slightly asymmetrical ears that let it locate hidden prey in the dark by the noise of its scurrying in the manner of an owl, though more primitive. In addition to live prey, all chamarmotoos also eagerly sip nectar and take fruit. 

They live in social groups,  and this is in fact the most strongly social group of all skuorcs, for they all not only care for their own young but those of others in their clan - and even males take part. Clans consist of bonded individuals, not random gatherings, which stay together and share food and territory. The females give birth to small litters of three to five babies at an earlier developmental stage than is typical, and these young can cling to surfaces but are slow and uncoordinated. They are put onto the back of the adults and carried around safely for over six weeks before they are fully independent, and during this time all adults in a group will take turns carrying them and giving them pieces of food. The young remain with their elders for longer still, sharing a common roost in a crevice in the spires or a hollow in a tree. They disperse to new groups around six months of age and can breed soon after; lifespan averages four to six years.

All species of these unique little animals are small enough to be held in one hand - tiny and vulnerable to all manner of predators if they leave the thick canopies of the sky islands. So with almost no exceptions, chamarmotoos never do. Some species have lived on islands as small as one square mile across for hundreds of thousands of years, and on larger ones a few tens of miles wide for millions. Most species diverged before the islands had formed at all, as the earlier, more widespread spire forests became broken up by increased large herbivore activity over the plains, with dozens of small populations left unable to meet as the trees were reduced to localized pockets that would later build up and out again into the sky islands. Very rarely, once separated islands will converge again through their growth over millennia and populations meet again, now too different to recognize each other, and generally avoiding interbreeding. This is common to the larger ridges, which have formed from the union of a number of smaller ones over many, many years. Smaller forests, some alone on the plains with no nearby neighbors, usually support just a single endemic species that is found nowhere else; if anything were to happen to its single home, it would die out.

This is true of the clown chamarmotoo and the leaf-crested chamarmotoo, both a species endemic to single sky islands. The former is wider-spread in comparison, and occurs over a single highly insular chain of sky islands over 300 miles and an ocean crossing away from any other on the real-island of Zarreland, which was previously connected to the mainland by a land bridge when the first members of the genus evolved. The latter, however, lives on a single island barely one square mile in size, and occurs entirely within the leafy crown of a single cementree colony located on the most outlying isle in the Trilliontree archipelago before reaching Trang Island. Both species have been rendered very different by their isolation, though they still fall into the same genus.

 The clown chamarmotoo is notable for its wide color range that includes multiple very different morphs. As the longest-separated species, more than four million years isolated from any other, it has evolved some distinct behavioral quirks not seen in other members of the genus including a very highly evolved song-like call in the males which are used to defend territories and attract mates. Clown chamarmotoo males are less directly involved in child-care than in other species, perhaps because Zarreland has even fewer predators than sky islands elsewhere, and males of this species spend more time displaying outside bonded female groups. Their routines include agile demonstrations of fitness in the form of jumping, twirling dances that bring attention to their bright blue tails. The males of this species usually display in groups of brothers, with one dominant one mating with the females and the others helping him drive off other males and keep the females' attention. This lets the subordinate siblings stay on their territory and avoid the dangers of dispersing, while not catching the strongest male's ire. These wingmen will likely eventually take the role of the dominant male when their brother dies, which he is more likely to do than them, for he spends the most energy on his performances, and is the least wary of any possible threats while doing so.

Living on the top forest of only one single sky island reef, the leaf-crested chamarmotoo is the most restricted species of its diverse genus. Yet it is a younger species than the clown, for it has only been here for three million years. Despite this, it is one of most distinctive species and looks very, very different from almost any other chamarmotoo. The single colony of cementrees it can be found in forms a small and completely insular sky island that reaches a maximum height of 250 feet, which has come to cover almost the entire tiny landmass it is found on from one shore to another over about 500,000 years. In that time has had little to no introduction of genes from off the island, meaning it is one of the most genetically isolated cementree stands in the world. This low genetic diversity, with all trees closely related, has produced a distinct phenotype in the trees, which have evolved characteristic white leaf veins and petioles not seen in the same species elsewhere. Inbreeding depression has also made the leaves of the trees here weaker and prone to developing distinctive dead patches, which begin as a yellow blotch and gradually turn brown from the outer edge in.  Living nowhere else and just as isolated as its tree, natural selection has driven the single form of chamarmotoo present here to evolve rapidly into a very different animal than its relatives and, even more fascinatingly, to converge in more recent times on the appearance of this specific tree population. 

Leaf-crested chamarmotoos are the smallest member of their genus, growing to only seven inches in length, half of this being their tails, and weighing one ounce. They spend their entire lives in the canopy of their island, feeding on insects and clinging to narrow branches. Their only predators here are birds, mostly small sparrowgulls, which are strongly visual hunters. This species has thus evolved very effective camouflage, coming over time to match the patterns of the leaves it lives in exactly, down to the white veins and dead brown spots. Though very active when hunting, the leaf-crested's sole defense against enemies is to freeze when it detects danger nearby, erecting a mane-like crest of feathers that almost doubles the height of its body to resemble a large leaf while spreading plumes on its tail that resemble a smaller one branching off. It takes note of the wind conditions, and even sways gently in the same pattern to completely blend in to its surroundings so that most hunters pass it on by. 

~~~

Not all chamarmotoos are isolated species, though. Cliff chamarmotoos are effectively the opposite of the leaf-crested: they are both the widest-ranging members of their genus, occurring across much of south and central Serinarcta rather than a few isolated islands as with many other species, and also are the biggest. This is because cliff charmarmotoos are the least arboreal species, and have instead adapted to live their lives on the steep edges of the sky island environment rather than the forest peak. Their thumbs are non-opposing, better to cling to vertical cliffs than grasp vines, and they are fairly large at over three times the size of the clown charmarmotoo, weighing two and a half to three pounds and growing to lengths of up to 32 inches. Their greater size, helpful to avoid enemies, also provides better endurance and lets them cross the ground more readily, resulting in its very wide range over thousands of years.

These skuorcs, like the rest of the genus, are mostly insectivorous, scurrying over the walls and ridges of the reef to snatch bugs that run over the same surfaces in great numbers. But they are big enough to hunt small birds and even molodonts too, and frequently do so, able to creep close with their mottled camouflaging coats and pounce at the last moment, swallowing all prey whole without chewing or dismembering and later regurgitating pellets of the indigestible bone and fur or feathers. They are mainly crepuscular, doing most feeding in the dawn and dusk hours when the flocks of birds arrive and descend from the cliffs they roost upon. 

Though individuals hunt alone, food sharing is well-developed and child-care is communal. Young animals kept protected in the den at first, but will later cling to adults outside it, and those adults which have not fed well on their own are fed by other members of the group via regurgitation after the evening and morning hunts. The relative abundance of food in such a colony and the strong parental instincts by all individuals, not just parents, are exploited in a novel instance of brood parasitism by another related species from the forests above the cliffs that, within hours of birth, transports its young to the vicinity of a cliff charmarmotoo's dens in the rocks and abandons them. As they resemble those of the host at such a tender age, they are often collected and adopted into the fold and put with their own young and there raised, saving the real parents' time and energy.  

By night family groups often play and socialize, with most sleep occurring in dens down deep mountain cracks during the daylight hours. These shelters, some of them going over 50 feet deep into the structure, are usually made in the first place of molodonts like the starrybara and then abandoned when their original owners were caught by predators, and are then passed down through the generations of cliff chamarmotoos in a family group. Cliff chamarmotoos are smarter than starrybaras and work collectively to spot predators like the skyheel with sentries, and to fight them off as a mob if they attack, which lets them take over these hiding places and hold on to them better than the animals that first made them. Yet not all enemies are easily kept at bay. 

When evening falls on the plains, the sky darkens first not from sunset, but the gathering of the mowerbirds from their grassland grazing grounds to the roosts atop the trees and cliffs of isolated sky islands - towering mountain-like structures built by cementrees over millions of years. These birds exist in numbers so vast that during migrations they can darken the sky above for days. But they are not immune to predation - far from it. The birds are at their most vulnerable as they enter and leave their nightly resting places. The cliff chamarmotoo hunts them as they come in to land, as does the skyheel, each jumping and diving to catch as many as they can in the short windows where they are most distracted and densely crowded, and for this short time these two enemies seem to forge a truce in pursuit of a common prey. Not everything that lives here has the willingness or capacity to do so, however - one of the most alien animals of all the sky islands is the bizarre and frightful cliff strikeworm - a highly derived pincerwing, and one of the biggest of all verminfan metamorph birds. 

Strikeworms, distant descendants of bumblebirds, are mostly represented by the large, neotenic female that grows to as long as 36 inches in length and never matures into a winged flying life stage. Instead, she is sessile, spending her whole adult life in a crack or crevice within the base structure of the sky island or within individual spire trees on its peak. She first holds on tight with two hook-like growths on the tip of her tail, later gluing herself in place, and stretching length-wise layers of muscles that cover her boneless body to strike out at passing prey, mostly small birds - and the chamarmotoo is just as edible as the mowebirds. She lunges out from her den at anything which moves and catches it in her sharply curved mandibles - structures that are derived from the wings of ancient ancestral birds. Once held, she injects a fast-acting protein-dissolving venom to quickly kill it, and retracts her body back into her hole, shortening her body to half its full extended length. There, safe from her own enemies, she chews into it with her  true jaws, located between her mandibles, and consumes it partially-digested by the venom she has injected that breaks the flesh down into a wet, pudding-like consistency to make feeding easier. Over 90% of the strikeworm's body - everything behind the tiny one-clawed hind toes - is comprised of the fleshy larval tail, which is hollow down most of its length and contains the stomach and some other organs of the animal. This coiled tail is what contracts and extends, effectively launching the small torso and jaws of the creature out of the burrow to snatch animals as they pass by like a sling-shot, and then reeling it back in. 

The female strikeworm is so large that she can't rely on passive skin respiration as her ancestors and the living juvenile larvae still do to breathe. She thus still develops a lung at maturity, but only one - her narrow, tube-like body cannot physically fit two. She doesn't acquire hardly any other adult bird traits, save for her gonads, and even remains completely blind to daylight, with her eyes nothing more advanced than a slightly light-sensitive bundle of cells buried in the flesh of her cartilage skull, the only ossified parts of which being her true jaws and her mandibles. She doesn't need her eyes to see, for the strikeworms have evolved something more effective for their needs. Four heat-sensitive pits are present along each of their mandibles that sense infrared light, letting them pick up the heat signatures of birds as they fly near their hiding places as far as three feet away - just enough time to launch themselves out in its direction and catch it. The strike occurs at about the same speed as a blinking human eye, fast enough to intercept the victim and bring it down before it leaves the small radius around its burrow in which the hunter can "see" it. The pits work by being lined with proteins that have become extremely sensitive to even the slightest increase in temperature, as when a warm body is just in front of them. When stimulated this way they signal nerves that connect to the strikeworm's brain, and induce the rapid decision whether to strike or to remain in hiding depending on the size of the heat signature (dictating whether it is prey or predator) and their own state of satiation; they will not strike if they have just fed. Though the minds of these birds are truly alien to other groups of life and developed very differently - and more simplistically - than those of other birds, the signals are perceived by the same parts of the brain that register visual input in other animals. Even without true eyes, the strikeworm can still see the heat signatures of its environment and of its prey, registering its world through a field of vision entirely limited to infrared - one most animals cannot see at all.

Males of the cliff strikworms's species represent the most extreme sexual dimorphism of any animal ever to live, living and functioning in every respect as a different species and indeed resembling a wholly different class of animal than their mate. A small, grey bird with a two inch wingspan, the male resembles a hawk moth and flies in a very similar way. It has large, dark eyes, a feathered body to keep warm in the cooler night air, and fully developed feathered wings in place of stabbing mandibles, but which still retain the unjointed C-shape, as they develop from the mandibles of a larva that closely resembles the adult female on a tiny scale. When it first emerges from its larval cocoon it spends about two weeks seeking flower nectar in the forest peaks of the sky islands and down on the plains, using this sugary food to build up fat reserves that will fuel it later in the breeding phase of its life cycle. When that time comes the males seek out receptive females in their cliffside hiding places by pheromones that they release into the air through glands in their mouths. The tiny, agile male detects these by scent with specialized fan-like feathers that grow behind each nostril and absorb molecules from the air, letting it determine the direction they have come from and pinpoint the female's location. Courting is nonexistent; males approach the female's territory and allow themselves to be caught, relying on the female's honesty in her intentions. If she has produced eggs, she doesn't envenomate the male, instead transferring him to be held between her spur-like hind legs and positioned against her cloaca so that she can transfer her eggs to him. The soft, shell-less eggs are tiny and resemble those of small fish- just a few hundreds of an inch across, but produced by the hundreds in typical verminfan fashion. Fertilization is external, and the male is released once the eggs are fertilized and glued to his plumage with a final secretion produced by the female, the same one she uses to adhere her own body permanently into her burrow once she becomes an adult, rendering it very hard for predators to pull her out.

The male strikeworm only mates one time in its life, and once released by its mate instinctively flies upward to the top of the island, seeking the scent of an active mowerbird colony. There, under darkness as the birds rest, he lands and digs himself into the substrate he finds, a mix of old soil and recent manure, and there dies of exhaustion some time after, his role complete and his adult lifespan of under a month at its end. The larvae hatch in under a week and take his carcass as their first meal, which if they are fortunate will be just enough to fuel their journey through the muck to seek out another dead bird, of which there are many in these great aggregations. As some chicks fall from their nests or adults are killed when too many birds roost on a single branch and cause its collapse, the larval strikeworms search them out by scent and feed on the remains, moving like earthworms just under the soil. They will spend between 4 and 6 months in this life stage before the male pupates and in a short time is ready to mate and complete a new generation. Females remain for up to a year before leaving the peak of the island and crawling down the cliffs to find a crack in which to hide. Unlike the male she undergoes no full metamorphosis, remaining grub-like but only becoming vastly larger. At first she travels between holes and crevices, and leaves them to hunt small insect prey that she smells or feels crawling nearby in the night, using the frequent rain to wet the steep surface so she can stick without falling. 

Eventually she finds a suitably large hole to spend her adult life in, however, and here adheres herself forever. This limits her to only what prey comes close enough to the entrance to reach out and grab, but also provides protection from outside enemies. Her metabolism stays slow and she can spend as much as 95% of the day in a hibernation-like state, waking only to hunt the mowerbirds as they come and go from their roosts. Then, for a few moments each day, seemingly barren cliffs come alive with the emergence of thousands of huge pinching worms that swing out and try to snag passers-by. It is only at this time that, in their enthusiasm, they might mistakenly strike at something much too big to be a meal, like an unfortunate unicorn. The strikeworm usually realizes its mistake quickly, however, and before wasting venom, so that the animal is quickly released, little harm done. It is not in its own interest to inject anything it can't itself eat. Yet every so often, a unicorn bleats and staggers... in a few moments it can no longer keep a grip on the precarious slope and tumbles over the edge, the unintended victim of an accidental envenomation. The toxin is so powerful, able to kill animals much larger than the strikeworm, for it is also used defensively against the birds that might otherwise try to pry the large females out of their holes with their beaks. 

And this is a good thing, because it renders her as one of the only animals, of any kind, which live on the sky islands that is not vulnerable to its apex predator, a creature of unrivaled size, strength, mobility and ferocity: the thunderbird.

The thunderbird is an imposing species of drakevulture that makes its home in the tree-dotted peaks of the sky islands, roosting and nesting on the high cliffs and preying on the unwary animals that cling to their cliffs and branches. The mortal enemy of skyland unicorns, an adult thunderbird is the feared enemy of all, an animal with no predators and a diet that can include anything from the littlest chamarmotoo to the largest unicorn. It is smart, adaptable, and very widespread, being a powerful flyer. It often takes advantage of the stormy hothouse weather to improve its hunting successes. It hunts most often during sudden deluges of heavy rain, knowing that the unicorns will be vulnerable to slip on the wet surfaces as they rush to sheltered crevices in the mountain. They also hunt quarry from within thick morning fog, descending out of the opaque sky suddenly and silently to snatch their victims off the rocks and carry them away in its jaws. Their beak is sharply serrated, each tooth-like edge functioning like a butcher knife to slice flesh and dislocate bone, and the beak is undershot, the longer lower jaw being useful to secure a firm hold on animals as it plucks them into the sky to prevent their falling out of the mouth as they struggle. They are incredibly powerful, their massive heads supported by a highly muscled neck, and they can carry a third of their body weight in level flight for several miles. Both sexes have tall, arcing head crests that are used for immediate species recognition at a distance and, in males, to demonstrate fitness through display.

Thunderbirds are aggressively territorial animals, living in monogamous pairs that defend wide territories that can encompass entire mountain ranges from rival pairs. Both sexes broadcast territorial claim with booming songs from high clifftops, usually at dawn and dusk when either mist or darkness obscure their makers so that the mountains echo with their disembodied voices. Battles between rivals, when they do occur, are often highly ritualized, and frequently take the form of spiraling dances between competitors in which both birds fly to a great height and then lock talons, spinning out of control downward at high speed. The bird which loses its nerve first as the ground rushes closer is vanquished and quickly retreats; occasionally though, two overly confident thunderbirds will hit the ground with a crack, breaking their necks on impact, and the territory will be left for the taking by others that may be waiting in the wings. A gentler, more controlled version of the dance is also the climax of the courtship ritual between bonding pairs and is then accompanied by a unique non-vocal roaring sound produced by the male as they spiral down to earth. It is produced by rattling of specialized tail feathers, the shafts of which are hollow, at high speed. From a distance, this sound - its origin usually unknown to those who hear it - resembles the approach of a distant thunderstorm.