The supercontinent of Panapterra technically ceased to exist two million years ago. The Ailox land bridge that once connected the two northern continents has been severed by tectonic activity. Ailuropia's eastward movement is still accelerating to this day, ploughing through the northwestern corner of the Loxodian plate. In response, the narrow strip of continental plate has fractured, with smaller fragments migrating north and south to get out of the way of the encroaching Ailuropian plate. Long transverse faults now carry patches of land out to sea and vice versa, resulting in a banded pattern of straits and islands.
It's difficult to overstate the biogeographic consequences of this event. Ailuropia is an island continent now, and it is already finding itself cut off from innovative new lineages like the facultatively quadupedal boxerbirds, who are quickly rising to prominence in the other two major continents. On the other hand, the oceans are more connected than ever. For the first time, nutrient-laden water from the boreal Perithalassic can enter the temperate pelagic region of the Medithalassic. This area was once a relative dead zone in Apterra's otherwise tropical and shallow central ocean, but now it supports a much greater biomass of surface life above its three-kilometer abyss.
For the life of this new archipelago itself, however, none of these great changes seem to matter. The islands have become the last home of several megafaunal bird lineages that saw their heyday in the Muricene. They seem to be takng well to the insular life, changing rapidly in size and shape to suit the cramped conditions. While their cousins are being rapidly outcompeted in mainland environments, they can still thrive in this final refuge of pre-Ice-Age ecology for a little while longer.
Grimbills (Ursapteryginae) are a subfamily of scythesnout kiwizelles that postdate most other avian fauna in the Accordion Reliquary. They saw their greatest success at the start of the Arthrocene, but they have suffered the same fate as many Muricene clades. Now, at the end of the Arthrocene, the hook-jawed carnivores can be found in only three places: as extreme specialists on the Northern Isle, in the northern seas in the form of the oceangoing sea scythes, and here. Like the Isle, the Reliquary has only one species: the Spiral Scythe (Helixornis reliquus). This genus was, prior to the rise of packslashes and bishears, common across northern Panapterra, but it soon found itself unable to compete for either pursuit or ambush predatory niches. The surviving species is smaller than its immedate ancestor but still larger than grimbills of the Early Arthrocene, reaching around 130 kilos. The spiral scythe is built both for climbing and swimming, as it must live nomadically across a wide range of fast-moving ocean passages and steep island cliffs. Its life in the Reliquary is not easy, and it is capable of reaching the mainland on both sides, but it cannot compete there. Instead, it sticks to the islands. On the coasts, it can find carrion and slow-moving marine tetrapods to eat. Carcasses of thalassaurs, giant fishes, and sea scythes attract as many as thirty spirals at a time, and they must compete firecely for every scrap. The hook of their lower bill forms a single blade that doesn't split at its base, instead emerging in front of the tongue and curving down into a pizza-cutter-like wheel that slices off large chunks of soft flesh. Further inland, large endemic birds are its main prey, followed by relict rodents. Around a third of its diet consists of high-quality plant matter like fruitgrasses and tubers. Its population no longer reaches above 8,000; therefore, while it is the largest land predator of the archipelago, it is far from the dominant one.
The terror kiwis (Aepyapterygidae) have two members in the Reliquary, a hypercarnivore and a generalist. The first is descended from the crescentbeak of the Panapterran plains. Its hunting style is similar to that of its ancestors as far back as 15 million years ago: a medium-distance pursuit followed by a single killing strike. Along with all other cursorial Aepyapterygids, it was driven off the mainland by packslashes and other carnivorns, overwhelmed by their greater social complexity and reproductive rate. This species is known as the Trident Kiwi (Tridontoapteryx reliquus) after the arrangement of its tusk-like face weaponry. Those of its plains-dwelling ancestor pointed out to the sides, but now they curve down like sabre teeth, following the same arc as the tip of the upper bill. They have fused with the rhamphotheca of the central beak, growing as one continuous structure. The three points are each up to 18 centimeters long, and though they are fragile against bending and twisting, they can deliver a precise bite to the spine, windpipe, or major blood vessel of the neck, avoiding a drawn-out struggle with prey.
Closely related to the crescentbeak tribe is the Polyrhamphus clade (Polyrhamphus spp.), which, unlike the trident, retains separate keratinous structures of the beak-tip and side tusks. Early polyrhamph species were small, cryptic forest-dwellers that ate large arthropods and small vertebrates. They now find themselves mostly outcompeted by microcarnivorns and pouchwings, except for the dozen or so species that live across these islands. While their trident relatives reach 35 to 45 kilograms, polyrhamphs range from 5 to 30, depending on the size of the island they live on. Polyrhamphus have next to no swimming abilities; they were stranded on their islands when the land began to tear itself into strips. They eat a mixed diet, supported by their multi-tool beak: the end of the beak is broad and faces downward like an incisor, allowing it to peel and pry, while three pairs of short penknife-blade-shaped rhamphothecae run along the sides of the snout, serving to cut meat into swallowable chunks.
Mammals are a minor presence in the Reliquary, with the exception of a local basketbuck radiation. Ailoxen (Ailoxtherium spp.) carry on the name of a place that no longer exists, with a range that still includes a few pockets of eastern mainland Ailuropia. They are another non-swimming clade that found themselves caught in the pleats of the Accordion, with insular species reaching between 10 to 40 kilos. All ailox species have a characteristic mane of dark fur that starts on the forehead and covers the shoulders, upper back, and most of the ribcage. This is both a status symbol and a defense against cold and windy conditions on the northern coast of former Panapterra.
By number of genera, the raspbirds (Phyllapterygidae) are the most biodiverse family of Reliquary megafaunal birds. The biggest is a newcomer from the graspbird clade. The Pegleg Graspbird (Dromolinguornis ungulatus) is Apterra's first ungulate bird, with toes and claws reduced to blunt hooves. With keratinized tongue "claws" to move obstacles, the feet are no longer needed for digging or scratching for food, so they have reduced in size to decrease drag, allowing the pegleg graspbird to become more cursorial. The insular subspecies, Dromolinguornis ungulatus minor, only reaches about 15 kilograms, and it has to stick to the shores, as it can't climb mountains on its inflexible club-like hooves. It eats vegetation of any quality, from dry basket-grasses to fruitgrasses and tree leaves, along with washed-up algae, small animals, carrion, and over 100 species of fungi. Adults are mostly safe from predators on flat ground due to their speed, and when cornered they can lash out in any direction with their lingual claws, so they are largely left alone. Eggs and chicks, however, are at risk of being taken by more than two dozen species if their parents aren't vigilant. They thus maintain a sparse population of 25,000 individuals around a few of the largest islands. Juveniles are sometimes able to disperse across water, maintaining gene flow between islands and even with the mainland subspecies once every few generations.
Only one species of raspbird still lives in Muricene-style nomadic herds: the Blue-Spurred Raspbird (Neophyllapteryx caerulunguis) is a social browsing herbivore that gets its name from the two pairs of blue-and-black banded spurs behind the feet of males. The blue comes from biliverdin, resulting in a dusty pastel coloration similar to the eggs of some chicken breeds. The upper spurs are deeply rooted into the tarsometatarsus and can stab (upper pair) or slash (lower pair) up to ten centimeters deep. Herds can grow as large as 150 members, and they regularly cross the straits on calmer days, passing through perhaps ten major and fifty minor islands a year.
The last of the Reliquary raspbirds is an extreme dietary specialist. This endemic species emerged from a small forest-dwelling omnivore that became stranded 2,500,000 years ago on one of the smallest, oldest, and farthest-flung of the islands, but it is now expanding its range, and it may one day return to the mainland with its new niche. The Lousemouth (Pholidotapteryx reliquus) eats social isopods, including both Pestilarthrids and Scansoriarthriforms. With few insectivorous rodents and small birds in its range, this raspbird has a nearly endless supply of crustaceans to eat. Social woodlice are an uncommon food source for vertebrates, who tend to find them overwhelming and unappetizing, but raspbirds with their derived tongues were particularly pre-adapted for this diet; they can pluck prey from a distance with little danger, using a mesh of barbed side-branches to ensnare up to twenty at a time if they try to mount a massed defense. This strategy has proven successful across several different islands now, and the total population has risen above half a million adults, each of which eats half a kilo of pill bugs a day. They've been unable to make inroads on either mainland due to competition with specialized insect predators of social crustaceans. However, if another major biogeographic event happened to interfere with the dominance of large carnivorous flies, the lousemouth seems poised to expand much further from its insular home.
Finally, the ruling giant herbivore of the Accordion Reliquary is the Aptegander (Apteranas colossus), a semiaquatic beakbuck species that reaches 800 kilograms, far out of the reach of any local predator. Though it leaves the area in the spring to breed on even smaller, more isolated islets further south, it spends most of the year feeding here, where huge seaweed beds grow below the low-tide line. In the water, few predators find it palatable, as it sequesters toxins from its food in its muscles and fat tissue. When not eating, it can usually be found hauled out on land, as it is not yet adapted to handle saltwater on its skin for a long time. This is the last member of its subfamily; when it is gone, so too will go the entire lineage of flat-billed kiwizelles that once blanketed the woodlouse-grassland.
In less than two million more years, the Ailuropian plate will reach the broad west coast of Northlox. A new land bridge will form, and the Accordion will be squeezed even further until it folds up into a mountain range of moderate size. Then, Ailuropia will grind to a halt, having shrunk the Medithalassic and completely demolished this refugial archipelago. Most fauna will have nowhere to go, and in total over 100 species are likely to go extinct. Of these, over 50 are expected to be downlings.
Downling diversity is gradually ticking downward worldwide. They still have just as many strongholds as, say, the Muridiungulates, but they are notable for just how quickly they seem to collapse as soon as pouchwings begin to encroach on their habitats. Right now, only around 20 species still survive in "conventional" perching bird niches on the three major mainlands, along with just shy of 100 across the large island continents. 50 can be found on small islands worldwide, and a further 50 just in the Accordion, for an overall species count in the low 200s. This is down from over a thousand before the rise of clutchbirds. With insular environments like Choeropica and Aglirium seeing greater and greater levels of dispersal from the mainland, it's possible that Apterra's last downlings will be found here, and not for very much longer.