Life at the Boundary

The Thermocene-Pangeacene boundary will go down as the most extreme, volatile, and devastating extinction event in the history of life as we know it - even more destructive than the Great Dying at the end of the Permian on Earth. More than 99% of life on Serina will be obliterated over the course of three million years.

We are only halfway through.

It is now 176 and a half million years since Serina's first life appeared, and the world of birds has suffered greatly. 1 and a half million years have passed since the end of the Thermocene, and the Pangeacene will not officially begin for equally long. The world, for now, is caught in the midst, a no-man's land of instability, of destruction, devastation and loss. For this is an extinction event comprised of countless extinction events. Nearly the entire world is already scraped of any life more complex than bacteria, through combination of volcanic eruptions, dust storms, soaring temperatures, intermittent ice ages, flash floods, plumetting oxygen levels, heightened radiation, and toxic gases produced by extremophile bacteria. This all comes from the recent collision of the continents, crashing together into a single, enormous land mass, producing huge up-wells of magma as they shatter together, and disrupting currents and weather patterns. The oceans are now virtually lifeless, tepid and stagnant, with no oxygen below immediate surface levels. The land is a vast, red desert of erosion and dust. A full recovery will take many millions of years.

The south pole is the only refuge in a world that could have died. A safety net, which now carries a wayward life raft of oddball survivors from one era now gone, into another on the far distant horizon. Here, and only here, temperatures have remained tolerable on account of the long polar winter, sheltering the land from the harshest rays of the sun through a weakened ozone layer. Every living vertebrate on land and the vast majority of invertebrates is now crammed together into a single remnant ecosystem the size of Illinois, but narrower, stretched like a ribbon along the coast where the last land plants are still nourished by its fog. The exact location of the refuge is ever-changing, as cooler periods produce ice caps and life migrates north; ice melts, and so life retreats south, a delicate dance of life through the depths of time. With each shift, some species fail to keep up, falling from the life raft. With over a million years left before the raft hits land, and the global climate at last stabilizes, only the strongest of all will make it.

The south polar refuge is an ecosystem sustained by the death of others. A brown food chain of nutrients, the remains of the dead and dying from elsewhere, now wash south along rivers, sustaining its plants and in turn its animals. Riparian ecosystems are among the most durable through extinction events for this very reason - on Earth, this brown food chain allowed even such large predators as crocodiles to endure events that killed all large animals on land, and so here, too, animals remain that are now long gone elsewhere. When the glaciers form, water runs south, for they deform the land with their slow, heaving movements, creating valleys that water pools into. When the glaciers recede, their meltwaters flood these valleys and rivers change course to run north, gouging out new valleys with their torrents. The nutrients shift back and forth along their flow, and the plants and animals follow. Each cycle, they flow stronger, through deeper channels. When this extinction event is over, the last glaciers will produce great floods over the world, rivers of freshwater that will flow out over the sea and into the continent's interior, transporting varied life to new homes. But that is still some time away. For now, this refuge remains small, fragile, but enduring.

Scavengers and omnivores fare best in the current conditions, and a handful of species, like the galliwalt-descended waterbirds called galligoots, the pseugull and shore-shriek (common coastal seabirds), the eelsnakes (several distantly related forms of semi-terrestrial swordtail fishes with serpentine bodies), and the strange, tentacle-beaked water snuffle, do very well feeding mainly on the lowest rungs of the food chain; algae and small invertebrates fed in turn by the refuse of other, dead environments that washes into their habitat. Others only barely eke by; mucks are slow moving herbivores and struggle to follow the shifting habitats, yet survive through their low caloric needs and ability to endure both flood and drought conditions. Tribbetheres and their ancestors, the hoppers, both endure, for with a flexible metabolism but long legs set below their bodies, they are a perfect medium of highly mobile and able to survive long periods without food; earlier forms of their lineage, the tribtiles and kin such as the burrowing desert tribbetoad also survive due to their tolerance for heat and limited food.

Metamorph birds persist in at least three forms, each one with a larva specialized to consume a different food source and utilize a different habitat. Of the three, the ambulopterans, with a leaf-eating larva, are most imperiled, yet also the strongest fliers when grown, letting the adults still manage to find their way to sparse, isolated remnants of forest. Their young feed on gluetrap trees, cutting the stalks of each leaf to stop the flow of defensive, gummy sap that would glue their mouthparts. They feed on this miserable fare because the only other alternative is the hostile ant trees. They are the dominant floral community along the edges of the valleys and ravines. Here, they can access the water and find shelter from the sun, yet be saved from the fierce strength of periodic flooding; only faster-growing, shorter lived plants - mostly varied grasses including fern-like feathergrass and toxic assassin grass, but also sunflowers, an utterly ancient and little-changed plant genus - now grow in any numbers in the bottom of the valleys, where nutrients pool but life is far more dangerous. Ant tree forests are planted by their insect partners, who collect seeds and plant them uphill of the parent tree, keeping them safe from the rivers might. And these trees swarm with aggressive symbiotic insects that quickly kill such pests as hapless metamorph bird larvae - yet even they struggle with dangers they cannot stop, such as wildfires that spark from magma and lightning, scorching whole forests in a matter of hours. All they can do to reduce this threat is to maintain gaps in their forests, bare soil borders over which flames, needing fuel to survive, may not be able to cross. This action by the ants spares the forest as a whole from instant obliteration. After millions of years of co-evolution, with trees providing home for these ants, the insects return the favor. Their careful gardening will save the ant trees from extinction.

Aquamorph birds, with swimming young, thrive for their larvae are also vegetarian but can swim, and thus feed mainly on algae, which grows even in the least healthy of waterways. Fish survive here, too, albeit in only a tiny fraction of former diversity. None remain from the oceans, not a single species. Only the most primitive, hardiest freshwater fishes remain, live-bearers like the original guppies and egg-layers, more resembling minnows: baitfish. Their close resemblances to each other are coincidental; both groups are paraphyletic, their members hailing from ancestors of wholly different species. Some livebearers are guppies, others mollies, and some swordtails. The same is true for the egg-layers. But it is hard, now, to tell the difference - convergent evolution makes distant relatives appear close, and close ones appear distant. Before, they were all little more than food for grander creatures. Now, they will give rise to every fish of the future seas. It is like their evolution has restarted, all the derived forms killed off to leave only the starters as if we returned to the Hypostocene. It will not be the last time the fish are so affected; their evolution on Serina will be one of several such starts and stops. It strongly favors the survival of primitive lineages, living fossils, and stalls dramatic changes, except of course in the tribbets, the most fully terrestrial fishes on Serina, and by far the most changed from their origins. Yet while fish remain largely static, a new lineage which appeared in the late Thermocene is a veritable alien in comparison. A snark, a squid-like, active predatory snail with hardly any shell, has survived the death of the seas by moving upstream into freshwater, along with such organisms as the sea bamboo, now the last vestige of a once widely successful clade of plants reduced to little more than pondweed. Now, the snark curiously eyeballs its closest living relative, a humble pond snail, that will soon become its next meal. The snark is unlike anything which has ever come before it, and yet remains adaptable enough to get by on the same meager food scraps as such ancient and unchanging species as snails, guppies, and crayfish, almost unchanged for over 150 million years. It is rare that such a new group can already prove itself so enduring, yet in this climate, it portends future success. This snark is only the beginning of a dynasty yet to come.

Verminfans, whose young feed on the flesh of the dead, thrive best of all metamorph birds, proliferating into swarms on the misfortune of others. And there is a lot to eat here, for death strikes all around. Among megafauna of the old era, almost all are gone. Fierce apex predators like tyrant serins survived only centuries into the beginning of the end, and only remain now as fossils eroded out of the new riverbeds by the flowing streams. Serilopes, perhaps the pinnacle of avian evolution in their time, only now become extinct. Isolated individuals still survive, against all odds, by following the refugia, but each shift brings them more losses. Any one cataclysm, they might endure. A shorter extinction event, if only by centuries, and they might pull through. But the collective devastation they together bring, and will continue to bring for another 1.5 million years, is just too much for them. An endling, the last individual of a species, has died an unspectacular death, caught in a flash flood. Its remains will now support the survival of others, scavengers unable to understand the gravity of the last serilope's death. But the vivas are not extinct; the bumblet alone remains, carrying the torch of its forebears. The bumblet, small and able to hide away underground from the sun and the rain and the wind, will make it through this drawn-out, long death.

Their lineage, along with the other most tenacious groups of the south pole refuge, will will go on, through this darkness, and come out one day in a new dawn.