The mid-expansocene: 75 million years post-establishment

Now, 75 million years after the establishment of chiroptosphere, another major change has just happened. While the southmost continent has stayed mostly the same, the northmost continent has just split into two smaller ones, the cold nordos and the tropical durios. Part of nordos has moved upward onto the North Pole, and the animals will need to adapt to this new, freezing, climate. Durios is once again supporting an extremely biodiverse major rainforest, but it is about to undergo a biological upheaval.

Fifty million years ago, a unique arms race between predator and prey was set in motion. The dromeolocators located their prey via echolocation, which involves making sound to pinpoint what is around you. It was not long before a clade of prey animals gained the ability to hear this sound, and the dromeolocators were forced to adopt a new sound frequency, which again forced the prey animals to adapt to hear it. Eventually, after many population booms and crashes, they settled on a solution- each individual would be distinct in the frequency they could hear or echolocate with, so that even if a small group of prey animals could hear the frequency a given dromeolocator used, the dromeolocator could easily find another group that couldn’t.

This had effects on the behaviour and lifestyle of each side of the arms race. For one, because different individuals in the same species could make and hear wildly different sound frequencies, it was difficult to communicate on a large scale, and so dromeolocators became mostly solitary and their prey lived in small family groups of 5-20 individuals. Because these small family groups could only make/hear the same small band of frequencies, or they would not be able to communicate, groups of them that could hear very different frequencies and use this ability to warn their other group members were not possible.

One interesting effect of all this was that the gazirolopes, giralopes, hyadonts, and rockodonts, all of which are prey animals that have special hollow horns they can use to make loud honks, would occasionally find themselves to be able to block the echolocation of a dromeolocator that tried to pounce on them, because their honks and the dromeolocator’s echolocation would share the same frequency. This never caught on, though, because even if they were able to block the echolocation of one dromeolocator, all others they would encounter would use different frequencies.

And so, this arms race continued for fifty million years- until, on the tropical continent of durios, one side would finally win.

The melodious gazirolope started out as a prey animal that could make two notes, not just one, with the resonating chamber inside its horn. It could do this by opening a muscular valve inside its nasal cavity, which changed the pressure of airflow inside its resonating chamber. This small adaptation would quickly become revolutionary. This arrangement could help it deter two different kinds of predators, not just one. While small, this was definitely an improvement over their one-note cousins, and they slowly started to outcompete them. So, they quickly started adding new notes to their arsenal.

Another revolutionary effect of their instrument-like horns was that they were now able to live in larger herds. See, only one of their notes would need to be the same, and they would only need to hear that note, to communicate. One species of melodious gazirolope came upon a very beneficial arrangement- they could play ten notes, one of which the whole species had in common, and nine of which they did not. They could only hear the note they had in common, and used it to communicate with other members of their group. When a dromeolocator attacked, all members of the group would play their other nine notes in tandem until they located a note that blocked the predator’s echolocation. Because they no longer relied on varied hearing abilities to protect their population, they could now live in larger and larger groups, which benefited them even more as it allowed them to gather more and more notes that might block the echolocation of a predator.

The ten-note melodious gazirolope was perhaps the most successful species in the history of Chiroptosphere. They quickly spread across the continent of Durios, outcompeting their relatives who could not so easily protect themselves from the dromeolocators. They spread so rapidly, in fact, even into forests, outcompeting the unilopes, that they became the only large prey item for the dromeolocators to feed upon. All the others were too small or too large or could defend themselves too well. And so, without consistent prey to feed upon, the large, apex dromeolocators of Durios went extinct. After a fifty million year long arms race, the prey animals had won. The only dromeolocators that remained on the continent of Durios were the smaller varieties that hunted chirats or hyadonts. And in the ecological vacuum that remained, three new predator species would fight to claim the spot of apex predator.

The speedonts

After the dromeolocators went extinct on the continent of Durios, there was an ecological vacuum in the spot of predator that needed to be filled. The rockodonts, as scavengers that already occasionally hunted prey if they could not find any carrion to feed on, were the most well-suited to adapt to the niche of predator. They would eventually evolve into the speedonts, predators unique for their ability to run fast enough to catch up to their prey.

The speedonts are the fastest animals in the history of Chiroptosphere, with their top speed being 120km/hr (74mi/hr). To reach these speeds, they have changed physically, with very long legs and an extremely flexible spine to add length to their stride, and short ears and a reduced trunk to make them more aerodynamic. Their long horn helps them turn at high speeds. Their sharp hooves are hooked on the end, which helps them get a grip on both the ground and their prey. Though they are less powerful than their predecessors, their great speeds mean not even the fastest prey animals can outrun them.

The grizzladonts

In the plains of Durios, the predator vacuum has been filled by the cheetah-like speedonts. But fast running is not a viable strategy in the forests and rainforests, and so another animal has had to fill that niche. The tuber-eating hyadonts, which occasionally supplemented their diet with carrion, have once again evolved into carnivores, but this time into the apex predators of their ecosystems- the grizzladonts.

The grizzladonts, despite being apex predators, will eat not just large animals, but fish, and some species even supplement their diet with fruit, mushrooms, and tubers. They are extremely large animals, ranging from the size of the black bear to the grizzly bear depending on climate. They are notable for their teeth, which extend past the front of their skull and onto their trunk. This tooth-laden trunk is extremely useful, and it is used to scoop ‘fish’ out of the water, pluck fruit off high branches, dig up roots and tubers, and of course catch and kill large prey.

The fearozinos

Since the extinction of the apex predator dromeolocators on the continent of Durios, the grizzladonts have evolved to be the apex predators of the forests and rainforests, and the speedonts have evolved to be predators that fill the cheetah niche on the savannahs and plains. But on the plains and savannahs, there is no apex predator. At least, there wasn’t, not until now.

The chirozinos are herbivorous forest browsers, using their arms and long neck to reach high-up branches. They are not docile, however- they have become wary of predators, and are highly territorial against members of any other species, using their menacing claws to scare off or maim trespassers. It was perhaps a highly territorial group that would kill and sometimes eat trespassers which would evolve into the new apex predator of the savannahs and plains of Durios- the fearozinos.

The fearozinos’ bodyplan is not very suited for fast running or particularly powerful pounces, but they are well-adapted for long distance running. They have supplemented this ability by losing their fur, which allows them to sweat efficiently, further increasing their stamina. The lack of fur left them more vulnerable to the sun, so they have evolved darker skin to combat this. Though they may not be able to outspeed or overpower their prey, they can chase it continuously until it collapses from exhaustion, at which point they will kill it with their terrifying claws. They often sharpen their claws with rocks.

Unlike most other predators in the history of chiroptosphere, they are social, hunting in packs. They are extremely co-operative, and will signal to each other with a basic language during hunts. Despite simple biological differences, like the male’s larger display structure, both sexes hunt together; though pregnant and weaning females, young pups, and sick individuals will miss out on a hunt. Disabled fearozinos, whether by birth defect or by injury, do not hunt, but they are usually still cared for by their pack. The fearozino is a terrifying predator to all but the largest animals, not just because of its physical capability, but also because of its social organisation.

Animals of the northern tundra

The ice giant is a species of chirozino that has reached sizes previously unseen for non-theropod bipedal animals. Their tundra habitat requires them to have large sizes and increased amounts of fat for cold protection, and their diet helps- unlike the rest of the chirozinos, which are fully herbivorous, the ice giants compliment their diet of sparse tundra vegetation with Chiroptosphere’s equivalent of fish. In the summer, they migrate south and feed on tundra grass. Though they were previously browsers, their comically long neck helps them bend down to reach low vegetation. When not feeding, they roll up their neck against their body. In the winter, they migrate northward, where the oceans are rich with small ‘fish’ feeding off the abundant krill. The ice giants stand on shore or lumber out into the freezing water and use their long claws to spear any fish that comes close. The deeper they go, the more fish they are rewarded with, but if they go too deep there is a danger that an orca-like predator might try to prey upon them. They will attempt to defend themselves from these predators with their claws, and the fights that ensue are often incredible.

The polar chirotaurs are a clade of chirotaurs; that is, flyers descended from fruit bats, that are more dainty on the ground than their echolocating cousins. Chirotaurs have been diving for food for tens of millions of years, and have even evolved long, beak-like snouts to help them snap up their fish-like prey. Polar chirotaurs take this even further, as though they can still fly, they have evolved to dive deeper and submerge themselves longer than any other chirotaur that has come before. To this end, they have evolved characteristics like short, round wings, webbed feet, and waterproof fur. Unlike birds, they cannot rest on the surface of the sea, so they have to spend their time closer to shore. Like birds, they make great nesting colonies on rocky cliffs, where the ice giants can’t smash their eggs underfoot. They can dive as much as 900 feet and stay underwater for as many as sixteen minutes in the pursuit of fish. They will often opportunistically feed on the corpses of ice giants.

The baleen chirotaurs are a clade of chirotaurs that feed on the krill-rich waters of the polar region. They are the largest flying animals Chiroptosphere has ever seen, the largest species sporting an eight-foot wingspan. They use this large size to support the massive head that they need to filter as much krill as possible from the salty ocean waters. They have two methods of feeding. Sometimes, they will sit in flocks of dozens in shallow water and scoop up as much krill as they can. When they have exhausted the stock of krill close to shore, they will effortlessly fly out to deeper waters, spending days at a time circling above the water and swooping down to fill their gullets, before finally tiring and returning to shore.

The next step: the late Expansocene