The Streaked Cavyhawk

 

While they have been around much longer and are still highly successful, the Pachyalatan Heteropods are not the only flight capable extant "bird" analogues on Athyrmagaia. Having denser bones than actual birds, Pachyalatans have higher body weight averages compared to Terran birds of similar dimensions, and are even more limited in terms of maximum size, the largest known non-flightless species only being capable of flight in short bursts. This proves to be disadvantageous, as it limits the altitude at which they can fly. It may have served them well over the past couple hundred million years, but it was only a matter of time until a more well-adapted competitor would colonize the skies.

Tracing their origins to an arboreal, predatory weasel-like Euathyrmatherian that lived in the canopies of a primordial Borean rainforest 73 MYA, the Polypterans ("many wings") initially started out as nocturnal gliders that hunted in forested areas. About 23 MYA, however, when the ancient forests started to recede and give way for great deserts, savannahs and grasslands, selective pressures eventually gave way to powered flight, and the Polypterans started to expand to a larger array of predatory niches, outcompeting Pachyalatan "birds of prey" and becoming aerial apex predators reminiscent of hawks and eagles. The complex modular, zooid-based biology of Athyrmatherians seems like it would be unfavorable and needlessly costly for a flying animal, but nonetheless the Polypterans have managed to modify this body plan to such an extent that they have become extremely effective fliers in their own right, managing to re-evolve powered flight independently from non-Athyrmatherian Arthropulmonians. This success is made possible by their possession of hollow bones and a unidirectional air sac system, which allows them to fly greater distances and achieve much larger sizes than their Pachyalatan competitors. At the moment, the Polypterans have left the other "bird" niches untouched, allowing for the continued existence of their apparently "inferior" Pachyalatan counterparts. If the right selective pressures take place, however, the Polypterans have the potential to replace the Pachyalatans entirely within the next hundred million years.

One family of Polypterans, the Rocida, has managed to give rise to some of the largest and most fearsome predators that ever took to the air. Named after the enormous elephant-eating birds of middle eastern folklore, the Rocids are a very diverse group of northern hemisphere predators, ranging from smaller eagle-like hunters of small monotherians and pachyalatans, to enormous, teratorn-sized predators that are large enough to kill livestock. The largest of these beasts tend to live in the mountains, where the absence of the more earthbound Polycarnivorans has given them to fill the role of apex predator in their stead. If their reputation as ferocious, almost mythological predators wasn't enough, Rocids also have a gruesome, if not downright disgusting mode of reproduction. Much like the flesh flies, the Rocids use the carcasses of their fallen prey as both a nest and a food source for their larvae, which are born moist-skinned and boneless before eventually emerging their hosts as composite neonates. Such a manner of reproduction would normally be unprecedented for animals of their size, but being Athyrmatherians, their multi-stage life cycles make this grotesque method of propagation a necessity.

The streaked cavyhawk (Deinopteryx agrestis) is an eagle-sized "solitary" Rocid endemic to the open grasslands of Borea. Though a comparatively small creature compared to other Rocids, it is still rather large by the standards of our own birds of prey, growing about as large as bald eagle at adulthood. It feeds on a large variety of smaller prey animals, with its main prey of choice being the prairie hopcavy (Batrachocavia gramineus). Despite its rather shrimpy size, it retains many of the same features as its bigger cousins. It has four wings, the primary upper abdominal pair being larger and used to create lift, and the secondary lower abdominal pair being smaller and used for steering like the tail fan of a bird. Both wing pairs are somewhat bat-like, and are comprised of collagen fiber and muscle reinforced patagium stretched out by elongated digits and a styliform bone in the elbow. Similar to pterosaurs, the upper wing pair contains air sacs that run down the length of the limb bones. When on the ground, the animal walks bipedally using the first wing pair as legs, bearing its weight on its thumbs and the knuckle of its second digit (first wing finger). Liftoff is achieved by vaulting with its wings. Uniquely among Athyrmatherians, the cranial zooid is directly fused to the thoracic zooid, and is unable to detach from the shoulders. The upper and lower "neck" tagmata are extremely lengthened, bearing a highly mobile elbow-like joint, and the auripods are located on the thoracic zooid rather than the neck. As an aerial predator, the streaked cavyhawk is well-armed for catching, killing and eating its prey. The labrum and gnathopods form a hooked, three-part beak with tooth-like serrations, with especially powerful "jaw" muscles that give the creature a powerful bite for tearing meat from the carcasses of freshly killed prey. The dewlegs of the thoracic and upper abdominal zooids terminate in powerful, recurved pincer-like claws used for grasping and seizing prey. These claws can exert enough force to break the bones of whatever unfortunate animal gets caught in its clutch. The smaller thoracic pincers house a pair of spinnerets, which secrete a fibrous silk used for nesting.

A "solitary" animal, the streaked cavyhawk lives most of its life on its own, and is highly territorial even towards towards other members of its species. They don't mate for life either, and as soon as the male finishes copulating, he leaves just as quickly as he arrives. The mother, on the other hand, is a dedicated parent, and looks after her offspring to ensure the continuation of her lineage. Like all Rocids, the streaked cavyhawk uses the carcasses of prey animals, specifically the prarie hopcavy, as edible nests for hundreds of maggot-like larvae that she births live. These maggots immediately burrow into the flesh of the carcass, and the mother suspends the carcass on a tree branch by wrapping it in silk, regularly marking the cadaver with a pheromone that serves as a deterrent for predators and scavengers. After about a week of feeding on the carcass, usually only a couple dozen of maggots of the original hundred survive, and twelve of them latch together in three groups of four, secreting mucus from their skin to form three composite cocoons. These cocoons, after twenty days of metamorphosis, hatch into three composite neonates that resemble snow white infant versions of their mother. From here on out, the mother cares for her three babies much like a bird would, feeding them pieces of meat from her kills. After about ten months, these babies grow into juveniles, and as soon as they learn how to fly they set off to live entirely on their own, reaching full maturity at five years old.