Ammit

The underground of Mars, sheltering its inhabitants from the harmful radiation and aridity on the surface, has become a refuge to many organisms. Some of which have no counterpart aboveground anymore, being relics of ages long past.

Ammit (Duatsuchus caecus) is one such relic, perhaps one of the oldest “living fossils” known from the planet. A relatively large carnivore at about one and a half metres long, it is assumed to be the last known member of a clade called Cancrisuchia, colloquially referred to as “crocstaceans”, archaic onychognaths that used their specialized raptorial arms for feeding. Some have compared them to Earth’s eurypterid “sea scorpions” in ecology and functional morphology.

In the fossil record, Cancrisuchia appears an unimaginably long time ago, in the Thermozoic Era, in the Argyrian, when Mars was still a semi-tropical ocean world and plant life was first starting to colonize the few strips of dry land. Cancrisuchians were among the earliest onychognaths to become amphibious, though unlike their later relatives, they mostly stayed at the boundary between water and land. Generally, they are thought to have been exclusively aquatic ambush predators, much as crocodylians and temnospondyl amphibians on Earth, and, once established in that role, dominated that niche for many millions of years. The key to their success lied, of course, in their raptorial arms. All archaeognaths lack teeth, their chelicere-like mouthparts functioning more like double-beaks. This limits their adaptability to carnivorous niches, especially compared to the toothed periostracans, which were at the same time taking over many marine niches. Cancrisuchians solved this problem by turning their first limb pair into another set of jaws, deriving from their shark-like scales projections which can for all intents and purposes be called teeth. Functionally these impressive “hands” can be settled somewhere between the claws of a lobster and the jaws of a crocodile, making for very effective weapons in grabbing and holding prey, possibly even further processing the food through careful manipulation by both hands.

Still, success does not last forever. The first major radiation of the Cancrisuchia, the Magnastracia, which included such impressive forms as the 7 metres long Deinoastacus, went extinct already in the Early Isidian, following climate changes. Their smaller cousins, the Microchelia, followed in their steps and over the course of the Thermozoic re-evolved comparably large sizes again. But these vanished too, at the end of the Cydonian, together with the large, reptilian thagmasaurs and various other lifeforms, in a massive extinction event whose cause(s) still remain mysterious. In the following Hylozoic, the role of aquatic ambush predator on Mars was largely filled by the so-called mangalasaurs, derived cuneocephalians unrelated to the cancrisuchians.

With that, it was long thought that Cancrisuchia is completely extinct. But the discovery of the ammit (made quite dramatically after it attacked a speleodrone) has seriously called that into question. While it is technically possible that it represents merely a case of convergent evolution from some unrelated lineage of archaeognath, the anatomical similarities between it and the fossils is too startling to accept that easily. If accepted as a genuine late-surviving microchelian cancrisuchian, on the other hand, it would open up the problem of there being a ghost lineage of these organisms that skipped the fossil record for two entire eras. Like in that old children’s story, it would be like finding a trilobite in your backyard today out of the blue.

One possible clue towards unravelling this conundrum is the fact that the ammit has (so far) only been found in flooded cave systems formed by the ancient lava tubes beneath Elysium Mons. If current palaeogeographical hypotheses are correct, then Elysium formed a slowly growing island continent throughout the Late Thermozoic and into the Hylozoic. We know for a fact (as far as facts go in astropalaeontology) that Elysium formed a refuge for other onychognath taxa during this time, such as the deltadactylians, which otherwise went extinct on the main southern continent. It could very well be then that some cancrisuchians could have survived on the former island as well. And perhaps these survivors adapted very early on to underground habitats, leaving little opportunity for them to fossilize.

Very little is known about the ammit in life, due to the inaccessibility of its habitat. Anatomically, its biggest difference compared to ancient cancrisuchians is the complete lack of eyes, attesting to a very long time adapting to the underground. Completely blind, its main sense organs are the long and specialized nasal and aural antennae. Like its ancestors, it probably is still an ambush predator, lying in wait beneath the surface of underground grottoes and lakes and waiting for prey, such as netchu, hekubus or medjed, to walk or swim by and be grasped by the raptorial hands. Any other behavioural or biological traits, including reproduction and activity, remain unknown.

Despite its fearsome appearance, due to a lack of resources underground, it must be leading an extremely slow, energy-efficient life, probably not moving for days, weeks or even months at a time and can probably go for years between feedings. A dim existence, living in darkness and a watery nothingness, unimaginable to the human mind. Though at the same time there must be some comfort, being all safe and cozy down there, unaware of the world slowly dying outside its shelter. Some may sympathize.

Does it even know that the oceans are gone?

Utigog and Medjed

Living in the caves of Mars must be both a dull and unnerving existence for tiny little creatures like the medjed. It is a simple, bipedal organism, without much of a “head”, whose daily life consists of scraping bacterial scum off cave walls. Not much outside that happens, though their lives are almost always ended violently. Not only may the arms of the speleotax lunge out of every crevasse but so too do the huge jaws of the utigog. 

The latter, as can be seen, is a close relative of the surface-dwelling ganguar. Whereas the ganguar is a placid herbivore, subterranean life has made its cousin a rather unpleasant fellow, its muscular jaws lined with long, needle-like teeth. Larger and stockier, more somnolent, it usually lies in wait inside burrows and waits for the right opportunity to strike out at unsuspecting prey. Though its single eye is well-developed, it also utilises long and sensitive vibrissae and eyelashes to sense its way through the dark world it haunts.

Not much else can be said about these creatures. Their subterranean life makes them difficult to observe and study for our astronauts. It remains interesting to note that the utigog and medjed are somewhat closely related. Both are members of the phylum Hemicalyxia, though the medjed represents the more basal members of the phylum, much like the netchu, while the utigog and ganguar belong to the more derived class Craniopoda. The medjed is also known to let out adorable little chirps, almost like a baby bird. How exactly it produces those noises remains a mystery, as it has no mouthparts except for a crown of tentacles. Perhaps there is some hidden bone-contraption inside the hemicalyx that produces the sound mechanically like a güiro. Likely the calls serve as mating calls through the wide caverns.

Speleotax

While the ancient caves and lava tubes protect their inhabitants from dust storms and UV-rays, they cannot protect them from each other. We have already explored the lithotrophic organisms which live here and the small primary consumers which feed on this microbial flora. Predictably there must also be predators that feed on them.

One of them is the speleotax, a quite large trichordate adapted towards life in darkness. Compared to its smaller, surface-dwelling cousin, its eyes are enlarged and reflective in order to utilize other creature’s bioluminescence and even the littlest bits of sunlight that might shine through the cracks in the lava tubes. Where that does not help, little, soft tendrils sprouting from its arms aid it in feeling through the darkness, like whiskers on a cat. While mute for the most part, perhaps using their three-pronged beak, speleotax are known to occassionally produce a sort of deep chirping sound which can endlessly echo through the caverns. Possibly, this helps attracting mates or communicating across the subterranean world.

Most of its “day” is spent hiding inside cracks and crevasses, either dormant or waiting for the right opportunity to strike at prey. For creatures such as the netchu, this must be creating an unnerving existence. Your whole life is spent in darkness, never knowing when an even darker shadow appears and silently pulls you towards a crunching death.

Under the Microscope

As on any planet, the majority of life on Mars is microscopic. Some of these organisms, such as the flechtoids, can form colonies large enough to be clearly observable without help. But most life is invisible to the naked human eye. Taking just a single droplet of Martian groundwater and looking at it through a microscope may therefore yield surprising results.

Most numerous in this unseen world are of course the areonts, the prokaryotic cells of Mars, who manifest themselves to our view as tiny specs slushing between the larger microorganisms. Some form small colonies, banding themselves into hair-like strings. To the north and south of our micromap we may see unusually large areont cells, one swarm propelling itself with single flagellae. The world of the areonts is itself interdependent with that of the Nanobacilli and the Areovira, who are so small that we cannot see them even at this scale.

Most conspicuous are the “elite” of the areonts, who form a kingdom of their own, the Macroareonta. These multicellular prokaryotes shield and compose themselves in all manners of siliceous shells. A quite large shell enters in from the north-west, the whole organism remaining obscure. East of it we see a smaller cousin in the form of a curved tube, from whose ends protrude a number of tendrils. Like their macroscopic cousins, these are likely autotrophic forms, though perhaps feeding on the waste and chemicals left behind by other organisms, for they live in lightless depths.

Quite different from these forms is the fellow which dominates the south-west, this hydraic pentagon. Using the tendrils which slither from beneath its shell, it drags itself forward and even entangles and strangles smaller organisms, the arms slowly devouring them with acids. This macroareont is what is called a “zoomorph”, in simplistic terms an “animal composed of bacterial cells”. It is not as organized as that may sound. Although moving as a single organism and encased in a single shell, prolonged observation has shown that the five compartments house separate cell-families that feed and nourish themselves independently of each other, making it more of a strung-together mass of rafts rather than a disciplined battleship.

This is in contrast to its relative we see in the south-east, encased in its mushroom-shaped shell. The cells-compartments of this “zoomorph” indeed appear to act in unison, with parts much more specialized for shell-building, feeding and reproduction and unable to exist without the others. Sagittabacillus, as it is called, has on occasion been described as a bacterial jellyfish.

Fierce competitors of these baroque organisms are the rhodokaryotes, chiefly the proteroareozoans. Their internal compartmentalization into distinctive cammaculae allows them more complexity and size even in a single-celled state. We see various of them floating around. In the very south is a malignant parasite that brings to mind a naval mine, seeking to attach itself to a larger areozoan or perhaps to be ingested. To its right is a three-flagelled “bottleship”, on collision course with its prokaryote counterpart. In the north-west, between the macroareonts, we catch a cell in the process of mitosis.

The contrast between the proteroareozoans and the macroareonts represents two different “philosophies” towards the attainment of complexity. One seeks it through external compartmentalization, the process of multiple simple individuals banding together to form one complex construct. The other seeks it through internal compartmentalization, dividing oneself into smaller sections to form one complex individual. This contrast forms, I believe, a universal pattern in nature. We see it repeated again at a larger scale when we compare the Polyfractaria with their relatives, the Pseudarticulata. On Earth too, when we contrast the great colonies of the ants and termites with the hulking bodies of the ungulates and pachyderms that both roam the remaining savannahs.

The highest complexity is however attained by those that can combine both internal and external compartmentalization. For evidence of this, look no further than Man himself, who in him carries the most complex organ the universe knows, which in turn allows him to form, beyond his own body, the most complex construct the universe knows: A society which puts to shame any organisation ever attained by the simple-minded colonial insects and produces intellectual and cultural achievements beyond those of even the smartest solitary animal. The terrifying side-effect, or perhaps result, of this compartmentalization is that Man’s potential for destruction is ironically only outdone by the most mindless and simplest of things, the nuclear forces which govern the very fabric of the universe and make even the mighty stars burst.

What we observe at the planetary scale of Man’s expanding civilization, we see, of course, repeated again at the microscopic one. Arezoans, the “animal” life of Mars, clearly outgun the destructive potential of both their single-celled forebearers and their macroareont prey. Three of them we see enter the picture in the north-east. On the very edge we see some sort of ciliated “brachiostoman” with a tail-fluke, using its tendrils to capture itself a unicell. To which new phylum of this broken up waste-basket-taxon it might belong is unknown. In some ways it resembles a miniature mollizoan without the distinctive jet-mantles. The fellow in the centre of the image, who is about to feed on some areont strings, defies classification even further. With its tendrils, mantle, cilias, vertical jaw and glide symmetry it combines traits from various known phyla and even kingdoms, making it hard to categorize for now. Perhaps this is a new phylum that has yet to be recognized.

More firm is the identity of the multi-legged organism, Noxochaetus, just entering into the lens’ frame. Its four-part jaws, four antennae and segmented body all indicate that this creature is a highly derived onychognath, likely a member of the insectoid Dodecapoda, who have reduced their six legs to such a degree that their expanded fingers now serve as twelve new limbs. Combined with the complete lack of eyes and extreme reduction in internal complexity (completely lacking lungs) to reach such a miniscule size, it is admittedly hard to see that this organism has more in common with an ushabti than any of the other worm-like organisms that inhabit the Martian soil. Noxochaetus represents the utmost degree of derivation, which ironically makes its playing field again that of the most archaic of Mars’ organisms.

Netchu

Many things live beneath the ground, in the ancient lava tubes of Mars. Often nameless things which gnaw at the roots of the planet, almost literally. Where the air is moist and temperatures are right in these dark tunnels, lithotrophic microorganisms thrive, feeding on ferrous and sulphurous minerals, sheltered from the dust storms and UV-rays on the surface. Where there once flowed glowing lava are now bioluminescent walls covered in a slimy moss composed of areonts and macroarenonts. Their waste is fed upon by pennatophytes and any airborne particles are filtered by sporians.

And where there is flora there will usually follow fauna. One of the more common animals in the lava tubes is the netchu, a rather funny-looking fellow, small enough to fit in the palm of your hand. Its body is an almost spherical cauldron supported by four tube-like legs which end in feet that resemble suckers or upside-down funnels. Atop the body grows a dextrous proboscis with a mouth at the end. The mouth is a simple tube which can extend into a lamprey-like maw, whose inside is beset with rings of little grinding teeth. These the netchu uses the scrape off and feed on the mossy walls. Similar tooth-like protuberances covering the soles of their feet, giving them excellent grip while climbing walls. The netchu has no visible eyes, instead there are writhing tendrils growing out of all the extremities, which the animal uses to feel its way through the dark corners and crevasses. Netchu are largely soft-bodied and capable of almost fully retracting their proboscis and their legs into the body, as can be seen in the right individual. Little is known about their general behaviour, as their habitat makes them difficult to study. Observations during winter time suggest that they survive by entering a deep sleep in which they likely breathe hydrogen, much like other cave dwellers. It is theorized that they reproduce by laying eggs (Schröckert 2301).

 Calyx of a netchu, with vestigial(?) leg bones.

Historically, netchu were grouped with a variety of other miscellaneous Martian invertebrates among the phylum “Brachiostoma”, which has however become invalid. The internal anatomy of these organisms played a large part in breaking up that waste-basket-taxon. Netchu have little in common with any of the Martian worms and, as may surprise some looking at them, actually possess an endoskeleton, albeit a simple one. The body is internally supported by a so-called calyx or test, superficially similar to what is seen in sea lilies or sea urchins. It is a bony box which encases the internal organs and offers attachment points for muscles. Unlike in echinoderms or vertebrates, this skeleton is only rudimentary. The calyx is open on top, allowing for the complete retraction of the proboscis into the body. The legs are supported at the base by single tiny bones articulating with the calyx, which serve solely as muscle-attachments, leaving the rest of the limbs soft-bodied as well.

Where that puts the netchu on the extant Martian family tree is a much-discussed question. The presence of an endoskeleton may put them somewhere close to the onychognaths or the trichordates, though the similarities are superficial at best. Similarly to the zitharta, some have taken the position of the cloaca, which is atop the calyx close to the proboscis, as a trait that might unify them with the Antitremata. This simply seems to be a case of convergent evolution, however. As in Antitremata, the posterior or ventral part of the body is internally sealed, albeit by the calyx in this case, forcing the gut to wind back up to the top to find an exit.

Out of extant animals, their internal anatomy instead puts them closest to a group of small bipedal surface animals called Craniopoda, to which belong funny fellows such as the utigog, tila and ganguar. These were previously classified as highly aberrant nothornithes or simply as incertae sedis, but their apparent relationship to the netchu and similar forms has opened up the opportunity of classifying them as their own distinct phylum. This new clade has been given the name Hemicalyxia. Of course, that still leaves open the question of their wider relationship status. Based on morphology, the closest relatives of the Hemicalyxia may have been the ancient Ambulostellia (Sivgin 2345), a phylum that is now thought to be completely extinct on Mars, being only known from fossils. Both may form a larger superphylum with the trichordates (Bomhoff 2340). If true, all three phyla seem to have descended from a radially symmetrical ancestor, distinct from the laterazoans (and without going first through a bilateral phase like Earth’s echinoderms). Though in Hemicalyxia we can observe a late bilateralisation, with basal forms like the netchu reducing their legs down to an even number and moving with bilateral behaviour and more derived forms like the craniopods becoming true bilaterals.

References:

• Bomhoff, Nils: A common, radially symmetric origin for the Hemicalyxia and Trichordata and the erection of the new superphylum Xenoradiata, in: Astropaleontology, 528, 2340, p. 85 – 101.
• Schröckert, Daniel: Fortpflanzungsweisen der marsianischen Brachiostomen, Bochum 2301.
• Sivgin, T.K.: Life on a Dead Planet. The first 3 billion years of Evolution on Mars, Zürich 2345.