Over the living edge

In a balanced ecosystem, herbivores usually make up the bulk of the fauna, while predators remain at lower densities due to the availability of food sources. However, this typical ecological dynamic is upended in the depleted environment of modern Antarctica. The few herbivores that remain often struggle to survive, facing harsh conditions that push them to the brink. Meanwhile, predators in this barren landscape face a stark choice: perish or adapt by turning to new food sources, primarily from the more bountiful marine environment. It is not surprising then that two of Antarctica's most successful predators, the antarctic ottofox (Glacicyon relictus), a descendant of barkdowners, and the banchisaraptor (Glacicuculus relictus), a descendant of ovoviraptors, are not only the last of their respective lineages but also the only vertebrates capable of thriving in both the Sanctuary Peninsula and the icy coastal regions of Land-no-Land. These two small predators, each rarely exceeding 6 kg, have evolved similar physiological adaptations to cope with the extreme cold. Both are covered in dense fur or plumage, undergo seasonal molting for camouflage, and have shorter limbs than their ancestors to minimize heat loss.

Despite their convergent adaptations, the ottofox and the banchisaraptor have different dietary habits that allow them to coexist with minimal competition. The Antarctic ottofox has a weak but rapid bite, preying on small animals usually no heavier than one kilogram. In the Sanctuary Peninsula, its main prey includes small rodents and micromammals, which it hunts by ambushing them near their dens. The ottofox uses its strong front paws to catch prey quickly and supplements its diet with plant matter, such as berries and seeds, during the summer months. In contrast, on the coasts of Land-no-Land, ottofoxes prefer heterogeneous environments featuring rocky cliffs and small patches of tundra, avoiding the most inhospitable coastal areas. Here, they mainly prey on nesting and resting birds during the summer and winter, respectively, and opportunistically feed on sea carrion, including fish, crustaceans, and reefsurfers. While they rarely hunt underwater, this is a skill more commonly seen in the banchisaraptor.

The banchisaraptor, a small flightless predator with a formidable bite force, can open the carrion of large sea organisms, which forms up to half of its diet in the sea ice regions. When actively hunting, it prefers reefsurfers and other aquatic birds, capturing them both on land and underwater. Its lobed feet make it an efficient swimmer and help prevent it from sinking in the snow. In the most inhospitable areas of Land-no-Land, where even birds hesitate to land, banchisaraptors can dive up to 10 meters to feed on shelled mollusks, which they crush with their strong beaks. Compared to its extinct ancestors, this banchisaraptor boasts the strongest bite force, thanks to its short but wide beak; a hammer-like adaptation like its predecessors would not allow to surgically chop down or crush frozen food. In large tundra or tundra-like patches, such as the Sanctuary Peninsula, banchisaraptors diversify their diet with terrestrial arthropods, microvertebrates, and even young stottmice, contributing to about 20% of their summer diet.

Both species are widespread in the highly productive Follia Plateau, though their numbers are kept in check by larger carnivores. This mesopredator suppression benefits microvertebrates, which thrive and are sometimes unique to this plateau due to the reduced predation pressure.
Despite the challenges, ottofoxes and banchisaraptors have proven to be incredibly adaptable, capable of surviving in some of the harshest habitats on Earth. Among all terrestrial vertebrates on the continent, these two predators have been the least affected by the Continental Crisis. 

Given the ongoing global cooling trend, if I would get a nickel for any antarctic terrestrial vertebrate that will survive for at least another million years, I would probably get two nickels...