Argantua

With Dixon-Darwin Boreal mostly devoid of large carnivores, some argusraptors turned their attention to the westward haglox, as there were no carnivores specializing in it. These argusraptors grew larger and larger, hunting older and older hagloxes, until they became large enough to take on adults. This produced the argantua, which split from its ancestor and grew considerably in size. After evolving in the mountains, it also expanded its range to include all other biomes which are home to hagloxes, though it is uncommon in the sparse Vivus Volcanic.

Argantuas generally hunt in pairs and will stalk their prey from some distance before ambushing them. They are not mated pairs, but rather siblings or unrelated friends that have known one another from a young age and are of the same sex. When hunting hagloxes, one draws its attention so that the other can rush in and bite at its neck, chest, or limbs without risk of being struck by their prey's powerful tail. Argantua mandibles are serrated like steak knives, so when the haglox struggles, it unintentionally aids them in cutting through its flesh and severing major arteries, causing the haglox to bleed to death. Similar strategies are used by juveniles hunting other species, but juveniles are also more cursorial and may chase down some prey instead of ambushing it.

As an adult, the argantua is largely featherless, apart from tufts along its legs and on the tip of its tail. Most of its body is covered in tiny chitinous scales, which are in reality formed from suppressed feathers. This gives its skin a leathery appearance and texture. Juveniles retain a covering of downy feathers, but these are shed as they grow older. Normally, in a temperate or montane region and especially one that is forested, fibrous integument would be retained in such large creatures, however the black trees absorb so much heat during the day that temperatures below the canopy in the dead of winter are more comparable to early fall at their worst, so a fully-feathered adult argantua would overheat for most of the year except in some high altitudes.

Adult female and juvenile argantuas are generally a similar color to the rocks found in their environment, so they may be mistaken for boulders. Adult males, however, are brightly colored all over, displaying their health and fitness to females. This is unusual for a superpredator, but a variety of factors have come together to allow for this vibrant sexual dimorphism. Adult argantuas only eat hagloxes, which are completely blind, thus there is no need to have camouflaged coloration to hunt them. An adult argantua is also so large and dangerous that their primary threat is other argantuas, rather than other species. The only notable predator they do have as adults, the twineshrog, uses pitfall traps instead of actively hunting, so their coloration does not increase the chances that they will be killed. The bright coloration begins to develop long before adulthood, but is initially restricted to the face and tail and spreads over the body over the course of 2 years. Old layers of chitin on the mandibles, shells, tail spike, and hooves peel away, causing them to fade towards the bright adult coloration. Though the full-body color transformation takes a lot of energy, the fact that a male stayed in good health and developed these bright colors is plainly visible proof of fitness, as disease and malnourishment during the color transformation is reflected by patches of grey or brown.

Argantuas mate once a year when it's warm enough, which translates to early or mid spring in the temperate regions. As they travel and hunt in pairs of the same sex, in general they mate pair to pair; a pair of males, after impressing a pair of females, will take turns mating with both of them. As a result, a single clutch of argantua eggs will usually have two fathers. The pair of males take no part in raising their young, as their bright coloration would draw attention to the nest, thus the pair of females raise them instead. They use their leg feathers and wing toes (which in males only serve for health indication) to incubate the eggs without crushing them. The babies are already half a meter long at hatching and follow their mothers around early in life. They hunt small prey on their own but stay close to their mother until they find a hunting partner, at which point they leave, however if they reach half their adult size before finding one they will be chased away.

The argantua is aggressive towards rival species, and it is the natural enemy of the twineshrog where their ranges overlap. When it discovers a twineshrog nest, it will immediately kick it to splinters with its hooves, and if the twineshrog within tries to flee, it will chase it down and stomp it to death. This is because twineshrogs are a major threat to the argantua, as falling into the pitfalls they dig is a guaranteed death sentence. When the argantua expanded its range beyond Dixon-Darwin Boreal, it also displaced some of the existing large carnivores in the Darwin-Vivus area. They completely wiped out the megajaw and the shikaaree in their range, and they have put considerable pressure on the bubblewraptor. Juveniles, which hunt smaller prey, have also caused the extinction of the scrubland hornface in their range by eating them all.