The Steppe Fenrir

 

Where there are herbivores, there are undoubtedly predators that hunt them. On Athyrmagaia's two largest continents, Borea and Comedia, the niches of warm-blooded macropredators are occupied by the Polycarnivorans, an order of Euathyrmatherians that are almost ubiquitous across both of the neighboring continents. The Polycarnivorans are divided into two major suborders that have representatives on both continents, the roughly canid-like Cynorhynchiformia and the bear or cat-like Cephalovenatiformia. A very fragmentary fossil record indicates that both of these suborders evolved as a result of geological isolation between two populations of a shared common ancestor, with the rising sea levels that followed the end of an ice age submerging an ancient land bridge that connects the two continents. The isolation resulting from the flooding of this land bridge caused the evolution of the Cynorhynchiformia on Borea, and the Cephalovenatiformia on Comedia. Eventually a second, albeit shorter ice age exposed the trans-continental land bridge once more, and the biotic interchange that immediately followed allowed the two lineages to immigrate between the land masses, with niche partitioning allowing some of these species to coexist. Despite a number of differences, there are a number of traits that unify the Polycarnivorans as a single order: most of them are Diontogenetic, possessing a bifurcating growth series where the runts of the litter never become zooids, instead setting off on their own to carve out a separate niche. Polycarnivorans also exhibit either a heavily reduced posterior sclerite or lack one entirely.

On Borea, the durable, hard-to-kill modular physiology of Athyrmatherian prey has provided selective pressures that favor cooperative or semi-cooperative hunting strategies. As a result, the most prevalent family of endothermic predators are the pack hunting Cynorhynchidae. The apex predators of many of Borea's habitats are the fenrir (Cynorhynchus lycanthropus), large, highly adaptable Cynorhynchid pursuit predators that rival our own grey wolves (Canis lupus) in overall size. There are several subspecies of fenrir that have adapted to various environments. One subspecies, the steppe fenrir (Cynorhynchus lycanthropus steppe) has adapted to hunt in the vast steppes and savannahs that comprise the middle of the continent, with their primary prey of choice being the mock ox (Xenobos borealis). Fenrir are exceptional predators, with both deadly weaponry and very keen senses at their disposal that allow them to track and apprehend prey. Their sense of smell is very powerful, and their olfactory turbinates so extensive that they partially wrap around their brain. Like many of our own predators, fenrirs possess binocular vision, with their eyes facing forward to allow for depth perception. Their auripods, ears derived from an internalized pair of limbs, are pointed and highly mobile, and are used to triangulate the origins of sounds. Their three-part beaks are attached to powerful muscles, with serrated tooth-like projections on both their gnathopods and labrum for slicing and ripping flesh. Sharp, blade-like internal mandibles and palatine papillae function a lot like carnassials, and are used to shear meat. The locomotor legs of the thoracic and upper abdominal zooids bear a hypertrophied, semi-retractable sickle claw on the outside of each foot, which is kept raised off the ground in order to prevent unneeded wear. The sickle-like claws are similar in function to those of our extinct dromaeosaurs, as the fenrir use them for prey restraint, hooking deeply into the hides of their prey with a deadly grip. Last but not least, the dewlegs of the thoracic zooid have evolved into raptorial limbs tipped with sharp, dagger-like claws. These claws serve as puncturing instruments for breaking the airtight mucus seals between their prey's zooids. Since a majority of Euathyrmatherian herbivores possess full color vision, dull and drab colors are not sufficient enough for effective camouflage. To combat this, many species of Fenrir (and a lot of other Polycarnivorans as well) use biliverdin as a pigment for their skin and hair, giving them a green color that allows them to more easily blend in with surrounding foliage. Steppe fenrirs in particular possess a vertically striped coat that breaks up their silhouette amongst the leaves of star grasses, which can range from green to a yellowish color. They also have seasonal coats; during the summer, their fur turns from green striping to white and brown striping to match the seasonal pigment changes of the grass.

When taking down large herbivores, fenrir utilize a highly coordinated strategy to ensure that every single zooid of their prey's body is incapacitated before they eat. Four fenrir attack from the sides, charging at the flanks before grappling with their sickle-clawed thoracic legs. Once they have a hold, they puncture the mucous seals between the body zooids with their raptorial arms, proceeding to rip out large pieces of flesh and pressure supporting adipose tissue from the edges of the connection surfaces with their jaws. As this happens, another pack member attacks the cranial zooid, biting the throat to rupture the hearts inside the neck. Eventually, the fenrir attacking the sides gouge out so much soft tissue from around the connection surfaces that the prey's coupling joints break due to the lack of support, causing the zooids separate and fall apart. From there, the pack members will start to feed on the still barely living zooids, plunging their serrated beaks into the delicate distribution membranes to more easily access the nutritious viscera.

Much like our own wolves, fenrir are highly social pack hunters that live in altruistic packs. The size of a pack may be variable between regional populations and subspecies, but usually a pack can range in size between 2 to even 12 members, with 4 to 7 members being the average. The pack structure is different from that of wolves however, with a much looser hierarchy where the members of the pack are more or less equals. Most species live, sleep and breed in simple underground dens, which are often dug near rocky outcroppings. As is the case for most Polycarnivorans, fenrir are diontogenetic, possessing both a zooid-based composite adult form and a smaller, non-modular paedomorphic adult form. Rather than setting off on their own to live a separate niche, however, paedomorphic fenrir remain as a part of the pack, and have a mutually beneficial relationship with their modular brethren. This mutualism is so tightly knit that they are able to recognize each other as the same species. Paedomorphic fenrir are called "denkeepers" and their role in the pack is to maintain and guard the pack's den as well as look after the developing offspring while the bigger and stronger fenrir are gone. As a reward for its contributions, the denkeeper is brought back its own share of a kill following a hunt. This social dynamic is completely unique to the Cynorhynchus genus. Pack members, fenrir and denkeeper alike, consolidate bonds by grooming one another.

Fenrir are oviparous, and females produce 25 miniscule, marble-sized eggs that spend half of their incubation period within their mother's body. The mother then lays her clutch in the den to spend the remainder of their incubation period under the denkeeper's watchful care. Eventually, the eggs hatch into separate unspecialized larvae that are born sexless. If all these eggs survive, 24 of these larvae link together in groups of 4 and then pupate, emerging as 6 composite fenrir "pups", becoming either male or female as they develop a composite body plan. The remaining 25th larvae, however, will remain independent, and grow into a denkeeper instead. Mothers feed their pups by regurgitating partially digested meat stored in their crop.