Dedrorax and Zyloron

 
A peculiar difference between Earth and Mars is the ways in which the local fauna has chosen the number of limbs on which to walk. On both planets there are plenty of bipeds, hexapods as well as creatures with no limbs at all. Outside of that, on Earth, animals have eight or four legs, whereas on Mars, tripods have evolved on at least two separate occasions while tetrapods are only secondarily derived from hexapods. What leads to such a difference? A popular explanation might be the differences in gravity, the heavier creatures of Earth requiring more legs for support, but so far nobody has been able to prove a direct causation. If it were true, it seems odd that the animals with the most legs on Earth are also all among the smallest and thus least affected by gravity, while hexapods are also abundant on Mars. Evolutionary history and contingency seems to be an equally strong factor, if not stronger. Periostraca ancestrally had only two limbs and so were restricted to bipedality unless also turning their tail into another limb, making tripodality their evolutionary “end-point”. However, the same restrictions would not have applied to the onychognaths, yet when natural selection called for the reduction of their limbs, they jumped straight from six to three with almost no transitional forms, which suggests there might really be an adaptive advantage to tripodality in the Martian environment.

A world apart from all of these discussions is an animal with no equal on Mars, let alone Earth. The dedrorax is a genuine monopod, at least when it has to be. When slow and idle it slithers across the desert, using its boomerang-shaped headshield to glide above the sand, but when in pursuit of prey or fleeing from predators it erects itself onto its muscular, bony tail, which ends in a three-toed foot, and hops away in wide strides like a kangaroo. When attacking its prey, it will extend a snorkel from beneath its headshield and strike out with a beak. From its back extends a retractable sail held up by bony rods. Perhaps it used in temperature control or social signalling.

Dedrorax are rarely observed and thus little is known about them, including their overall behaviour and reproduction. For a long time it was even unknown to what family tree it even belonged, as it seems to combine traits of many lineages, sort of like a Martian platypus. It has simple been considered incertae sedis. Close comparison to some other strange creatures offers at least some clues. The dedrorax has a partly siliceous endoskeleton and spine-like protrusions supporting its eyestalks, as well as a triradial cloaca in front of its sail. The beak at the end of the proboscis is three-pronged. These are all traits it shares with arezoans such as the arctic sortax. This points towards it being a highly derived member of the Furchordata, perhaps even the most derived trichordate of all time. How exactly this led to its evolution as a monopod is, however, not clear. Perhaps its ancestors were able to erect themselves and strike out on their tails like cobras and some unknown selective force reinforced that ability?

Among the reported prey of the dedrorax is the zyloron, a member of the verticutian dust slugs. It and its close relatives have lost their ancestral pseudopods and instead move much like serpents. They themselves predate on smaller onychognaths. Their armour has been reduced, something they compensate for with speed and being able to quickly bury in the sand.

The Great Orm of Mars

Fig. 1: An alleged photo of a sandworm briefly surfacing, captured by the Curiosity rover. In reality it is a rock formation of crystals whose surrounding matrix has eroded away.

 

The majority of life on Mars is tiny to microscopic in size. The number of lifeforms than can grow taller than a human can be counted on one hand. Any megafauna has been extinct for millennia, if not for millions or even billions of years. Or has it?

Rumours abound of the great dustbowl desert of the northern hemisphere being home to a gigantic creature that swims through the sands like a whale through water. These rumours of “sandworms” are largely based on grainy satellite imagery, geological structures claimed to be “worm-signs”, including the infamous canals, and some eyewitness-reports made by space tourists. At least one Mongolian cosmonaut claims to have seen one as well, likening it to the “olgoi-khorkoi” of his homeland. Professional spacefarers of western countries have meanwhile never made such claims (though even if they did see one, they might not report it out of fear of being seen as unprofessional, as often happens with UFOs). Nobody has ever been able to produce any physical evidence or even clear photographs of the creature.

There are various reasons that speak against the creature’s biological reality. For one, it seems physically impossible for an organism to move through sand as if it were water, especially at the claimed great speeds. Sand simply does not work that way and even if it did, the friction would create an unimaginable amount of abrasion and heat that would likely damage most organisms. At least one cryptoxenologist, Roy Sanderson, has countered this by claiming that the worm might be able to create vibrations in the ground that turn sand into a non-newtonian fluid that makes it easier to swim through. If this really were the case though, seismometers at various Martian research stations would have surely picked up evidence of such vibrations.

Even ignoring that, there is the question of how an organism this big would even be able to subsist in a biome with so little plant and animal life. Some cryptoxenologists have argued that in the deep underground of Mars there might be hidden lush ecosystems that the worms might be feeding on, like sperm-whales diving into the abyss to catch squids before surfacing. There is no evidence for these hidden ecosystems, so this is just special pleading. A more sensible suggestion that has been made is that the sandworms might be lithotrophs, literally feeding on the iron dust they plough through, because we actually know these types of organisms exist on Mars. This has led to some fanciful speculations that the worms might be giant offshoots of the otherwise small dust slugs. The problem is that the iron-reducing lithotrophy of the dust slugs is an inefficient energy-source that seems very unlikely to be capable of supporting any larger animal. Though we do not know how this system changes if an organism with a larger gut is able to ingest far greater amounts at a faster rate. Similarly to hindgut-fermentation in sauropod dinosaurs, larger body sizes might actually make digestion far more efficient than in smaller animals. But this is just speculation with no direct evidence.

Lastly, even if it is on another planet, it seems highly unlikely that an organism this large would go undetected for so long. Even if they lived 99% of their lives underground, the movements these creatures would create would, as mentioned, surely be detectable by seismometers.

Fig. 2: Satellite imagery claimed by Holland to show a giant worm or wormsign.

But if these sandworms are mere myths, then why do people keep claiming to have seen them? Perhaps the very first claims of giant sandworms on Mars, certainly the first ones to be widely published, were made by one William T. Holland in December 1978, based on grainy satellite imagery he claimed to show the worms and traces left behind by them. The images in reality just showed dune-filled canyons, which appeared convex instead of concave due to lighting. However, the date of Holland’s claims is highly intriguing, as they were made just a few months after the release of part 1 of Alejandro Jodorowsky’s epic Dune quadrilogy. Just like the novel they were based on, the movies prominently displayed the fictional giant sandworms of Arrakis, brought to life thanks to H.R. Giger’s amazing designs and Phil Tippet’s ground-breaking go-motion technology. It seems very likely that Holland’s interpretation of the images were coloured by the movies and their popularity among general audiences further boosted the perceived plausibility of the cryptid. Many of the space-tourists who claimed that the unusual sand dunes they saw crawl across the desert were the legendary worms admitted to having read Holland’s books on the matter, so their interpretation was thus indirectly also coloured by Jodorowsky’s Dune. Therefore, they all saw giant sandworms on Mars because they wanted to see them.

Fybra

 
The deserts of Mars are treacherous, not just because of the sharp and craggy rocks and the constant risk of massive duststorms. Under some rocks can lie predators who do not like being awoken from their hibernation.

One of these is the fybra, a serpentine organism that can grow up to 60 cm long. It is a fyrm, a group of derived diplognath circulates. Like the hekubus, it is a soft-boded organism internally supported by a hydroskeleton, not unlike a rainworm. Its only hard-part is the skull and the two dorsal mandibles, made of calcite. Unlike the hekubus, fyrms have teeth and are covered head-to-tail in a dense pelt of setae-derived hairs. They evolved this insulation because they are actually endothermic organisms and therefore try to maintain a stable body-temperature.

Requiring more energy than cold-blooded animals of similar size, the fybra is relatively rare compared to onychognath predators such as the tynus or even the much larger cecrops. But its metabolism gives it one deciding advantage: It can hunt during the cold desert nights when others cannot.

Most of its prey consists of spirifers, pseudarticulates and small onychognaths. How exactly it tracks them is still a mystery. It probably does not see in infrared like some snakes can, as most of its prey is not warm-blooded. Its sense of smell is likely also not well-developed, having no nose beyond perhaps two breathing orifices at the base of the skull. Most likely then it tracks its prey through sound, using its large and solid lower jaw to pick up vibrations in the ground. Perhaps it is even sensitive enough to pick up the heartbeats of certain creatures while they sleep, as the fybra is often observed preying on them lying dormant in their burrows. As the fybra cannot dislocate its jaw like a snake, it uses its double mandibles to cut up its prey into nice bitesize pieces to swallow.

During the long dust storm months of winter, the fybra itself hides underground in burrows in order to hibernate. While it can dig by itself, it prefers to seek out burrows that have already been dug out by other creatures, such as shetaws, a kind of tortoise-like archaeocephalian.

How fybras reproduce has not been observed so far. Probably, like other fyrms, they lay eggs.

Hrypidex Rannu

Nothornitha are a clade of the Periostraca, characterised by using their limbs to bipedally walk upright with a gait comparable to that of birds (hence the name). Modern nothornithes are traditionally differentiated into two separate groups: the bennus and the rannus. Whereas the bennus have fur covering their bodies and often a reduced tunicine tail, rannus represent the likely more ancestral condition of having a naked periostracum and a more elongated tail used for counterbalance. This goes hand-in-hand with metabolic differences as well, with bennus being endothermic, while the body-temperatures of rannus are more often influenced by the surrounding environment. Various skeletal details have also been identified in the skull, foot and carapace that supposedly set the two apart (more on that later).

The hrypidex is one of many different rannu species, though it is among the better-known ones. It is commonly found around the desert edges and oases of the great northern dustbowl desert. Its curved foot-claws, raised orbital bulge and secodont scolecodonts easily mark it as a scavenging and predatory animal, mostly feeding on smaller creatures such as archaeocephalians or dust slugs. It also frequently enters into squaffles with thecocerates such as the cecrops, though this has been characterized as less of a predatory behaviour and more of a rivalry between two predators competing for the same resources. Rannus usually come out on top during such conflicts, as their tooth-derived beaks are not only more formidable weapons than the keratinous beaks of the thecocerates, but they are on average also just much heavier than the lightly built onychognaths (the internal skeleton of periostracans essentially being a tortoise on two legs, only able to walk thanks to Mars' lower gravity). Cecrops can usually only retaliate by raiding the nests of rannus, but that is itself quite risky. Although not as sharp or active as their more derived bennu-cousins, rannus can make for excellent parents, closely guarding their nests until the young are old enough to feed themselves. Many rannus raise their young in pairs, but the hrypidex usually nests alone. The parent is usually determined through a mating ritual, where the distinctive crest of the pseudoskull is shown off in a nodding motion.

Returning to rannus in general, it is probably wrong to separate the Nothornitha simply into rannus and bennus. Most likely, rannus are a paraphyletic grade out of which monophyletic bennus (whose clade would be called either Eunothornitha or Avidonta in this model) arose (Sivgin 2345). Archaic rannu-like creatures, referred to as “Barocrania”, were the dominant animal group on land during the Hylozoic Era, their fossil members usually being split into the clades Carnornitha, Segnornitha and Rhynchornitha, whose members could sometimes reach sizes that exceeded those of Earth’s dinosaurs. Avidonts (or at least organisms appearing to be avidonts) do not appear in the fossil record until the Early Kaseiic, the last period of that era, descending either from small carnornithes (Hermann 2201) or the segnornithes (Krätschmer 2213), depending on what researcher is asked. Extant rannus are largely seen as still-living archaic carnornithes, though some researchers assert that a few could also be surviving segnornithes (the placodont, shield-skulled rhynchornithes seem to have gone extinct with no descendants).

This classic paraphyletic model has also been called into question, however, as we largely lack genetic data to potentially affirm or falsify it. Trace fossils and controversial body-imprints of Kaseiic barocranians possibly show that these had already developed a fuzzy periostracum long before the appearance of Avidonta, meaning that the insulating fur of bennus is not a derived but an ancient trait. Many extant forms also freely mix rannu- and bennu-like traits, such as combining a long tail with fur or the other way around, while also showing a mosaic of cranial and pedal characteristics from both groups. Samuel Leidy has thus recently proposed the quite radical hypothesis that classic “barocranians” have gone completely extinct at the end of the Hylozoic and that the bennu-type avidonts are the only surviving nothornithe lineage. In this model, the rannu-type animals we see today are actually derived bennus that secondarily (and perhaps even independently of each other) lost many traits associated with endothermy, possibly as an adaptation to the worsening habitability of Mars. Leidy’s modest proposal has been met with criticism by fellow astropaleontologists, though the results from recent molecular studies have been interpreted by some as potentially supporting this model. Only further research may clarify how these organisms are linked to their past.

References

• Hermann, David: Dental and pedal anatomy of Syntarsornis kasaiensis (Ceratornitha, Carnornitha) and the origin of bennus, in: Journal of Astropaleontology, 112, 2201, p. 34 – 67.
• Krätschmer, Daniel: Avidontomorph cranial anatomy in Micrornis gracilis, in: Journal of Astropaleontology, 123, 2213, p. 61 – 66.
• Sivgin, T.K.: Life on a Dead Planet. The first 3 billion years of Evolution on Mars, Zürich 2345.