Rhinoceros Warhoon

Archaeocephalians come in many forms, one of the most distinctive perhaps being the rhinoceros warhoon (Rambisaurus stamperi). Why it has that common name is obvious. The front part of the cephalon, the rhinotecum, is not just radically elongated, but also curves upward to form a sort of horn. What exactly this horn is used for is unfortunately not entirely known, despite extensive observation of this species. Kirkhope’s most extensive study so far has concluded that the horn serves a solely visual function, being basically a flagpost that the warhoon uses to flap and flutter its antennae from, either as a warning or mating display. Some accounts do, however, mention warhoons using their horns for interspecific pushing-matches, very much like stag beetles on Earth, which is sometimes stated as a fact in pop-science books. But these accounts are purely anecdotal and this behaviour has yet to be confirmed in a scientific context.

Rhinoceros warhoons mainly inhabit the dry slopes and shrublands surrounding the western Tharsis plateau. They are quite hardy organisms adapted for tough times. A large part of their gut is dedicated towards storing water, much like a camel, and their thick hide and osteoderms are excellent at preventing evaporation. They are extreme omnivores, their robust cheliceres allowing them to bite through the hard skin of succulent flora, as well as splitting the bones of any animals smaller than them. On occasion they have been observed lapping up bone-marrow with their tongue or even grinding up certain minerals. Their skin is also thick enough to allow them to feed on the predatory red weeds without being stung by their syringe-like urticating hairs.

Characteristic for the warhoons is a dorsal armour composed of multiple osteoderms, which may serve multiple functions. It obviously provides protection from certain mountain predators, such as smaller ballousaurs, but may also serve as a mineral storage or anchorage for certain muscles. Interestingly, the osteoderms are strongly infused with silicon dioxide. This has been interpreted as a form of protection against UV radiation, which poses a bigger danger on Mars than on Earth, especially at the high elevations that the warhoon lives on, as the lower amounts of oxygen on the planet also mean a weaker ozone layer. Silicon dioxide, in other words glass, is very good at blocking at least UVB rays.

On the topic of siliceous bodyparts, warhoons exhibit multiocully, meaning they have more than one pair of eyes. This is exhibited by multiple different onychognath groups, which could mean that it either was beneficial enough to convergently evolve or may actually be the ancestral trait. The benefit is obvious, as onychognath eyes are solid and are asymmetrically shed and regrown to get rid of scratches. The more eyes one has, the less the vision is impaired during these replacements.

Compared to other Martian animals, relatively much is known about the reproduction of the rhinoceros warhoon, thanks to Kirkhope’s work. The mating individuals determine impregnation through antennae-displays and head-nodding, upon which internal fertilization follows. Warhoons are viviparous and develop multiple uterine eggs, but usually only one or two of these eggs fully develops, nourishing itself on the yolk of the surrounding eggs once it has used up its own. Pregnancy can last up to one or two Martian years, depending on the altitude and availability of food, the warhoon being able to pause the development of its embryos if conditions are inconvenient. Once born, the young are fully developed and capable of living on their own.

Rhinoceros warhoons are often noted for their resemblance to the Antennarhynchi, a group of archaeocephalian tagmasaurs from the Cydonian period, to which the famous Tapinotherium and the Glyptosauria belonged. These likewise possessed an upturned rhinotecum and extensive body-armour, though they walked on erect legs instead of splayed ones and were the size of military vehicles. But this resemblance seems to be entirely convergent, as the finer skeletal anatomy of Rambisaurus shows that it is closely related to modern, lizardine onychognaths like the tynus (Sivgin 2345). Nonetheless, studying the function of the warhoon’s horn may allow insight into how these extinct aliens may have used theirs, as similarity in form likely implies similarity in function.

References:

• Kirkhope, David: Life cycle and Ecology of the Rhinoceros Warhoon, in: Areobiology, 195, 2294, p. 94 – 108.
• Sivgin, T.K.: Life on a Dead Planet. The first 3 billion years of Evolution on Mars, Zürich 2345.