Hadropotomus

A very large thorngrazer, the hadropotomus survives alongside cygnosaur rivals by specializing toward a habitat few others have managed: the water.

The hadropotamus is a species of semi-aquatic crested thorngrazer from the northern soglands that comes as close as their lineage ever has to be able to swim, though they actually walk along the bottom of shallow water bodies, using a jumping motion to surface in order to breathe, and cannot truly float. Using water to support their weight while feeding on a diet of submerged aquatic vegetation, they reach weights of 2,500 lbs, and are the biggest of all thorngrazers now or any time before, a size so large they can move only slowly and with great hassle over land. To walk they support themselves with their forelegs alone each time the hind leg is pulled forward in a cycle that involves a highly flexible spine, and a lot of sloshing of gut contents; the latter is somewhat alleviated with thick belly ribs that keep the abdomen more stable, common to all thorngrazers but extra prominent in this group. Still, their size and a formidable temperament, as well as social group-living, provides some protection from threats while out of the water. Such forays are done only rarely. The northern soglands of central Serinarcta, unlike the southern region which has become a wooded savannah by 285 MPE, is still a large and unbroken wetland region now known as the upperglades. While it too now supports more trees than in earlier times, it is still flooded and damp, and so here the species can still traverse the many rivers and waterways of its swampy habitat so that travel across dry land is rarely necessary.

These huge animals have adapted the nasal crests characteristic of their group into a novel and practical role - a long snorkel that lets them stay hidden underwater and live in deeper lakes than would otherwise be possible. The crests of the hadropotamus are fairly straight, fused, and positioned side-by-side, without spiraling or weaving together in any way that would shorten their length upwards to reach air. Both sexes thus have equally large crests, but males exhibit a bright pink dewlap that stretches from the tip of them to the upper shoulder. With a distinct camouflaging green skin pigment - produced from biliverdin, as in the sawjaws - the roughly triangular crest contrasts sharply, and has been described as resembling a sliced watermelon, all the more so in some individuals in which it is marked with small black speckles. Due to its practical use, hadropotamuses are the only crested thorngrazers born with the start of their crests; in this species it is very flexible and composed entirely of cartilage at birth, allowing the baby to pass through the birth canal. It hardens into solid bone at its base over the first year of life, but remains pliable and even mobile at its tip throughout life, with a muscular flap that can be sealed to keep water out while diving. In addition to feeding on submerged vegetation, hadropotomuses dive to escape predators. Their great size and aquatic adaptations mean they have only a few, but the subjugator is the most significant, for it can hunt them even below water. Juveniles, if they stray from their mothers, may also be hunted by river dragons, carnackles, and snagglejaws; semi-aquatic, bear-like foxtrotters descended from the triyenas. 

Hadropotamuses are basal crested thorngrazers, their last common ancestor to other species being the rumbling helmethead of 275 MPE. Their stomach is thus less strictly herbivorous and the diet broader than others, composed of water plants, crustaceans, fish and carrion. Though these animals mostly spend their days grazing, they are capable of ambushing small land animals at the water's edge and crushing them in their jaws, and pregnant and child-caring females are more likely to turn carnivorous to get nutrition for their developing young. Calves eat an even greater percentage of animal food, mostly slow-moving molluscs and arthropods, which make up 60-70% of its diet. Adult males are the most herbivorous, eating 80-90% plant matter. 

The mating call of the hadropotomus is a low foghorn-like bellow, repeated frequently, and is not musical. Calves meanwhile communicate with their mothers with high-pitched, nasal honks that sound like bicycle horns.