Perchloraven

The toxic salt deserts of Mars are not home to many animals, most of them being small-to-microscopic extremophiles. But some creatures have learned to exploit the hostile landscape. In the northern hemisphere we have already encountered the caraxor, a flying pedicambulate which rules alone over the perchlorate wastes there.

In the wastes which pepper the highlands and tundra of the southern hemisphere can be found an organism roughly equivalent in ecology but highly aberrant in every other aspect, appearing like the Martian parody of a flamingo. The perchloraven is a member of the rare and elusive Monopoda, which are secondarily flightless ballousaurs. For whatever reason, their wings (former hindlegs) have atrophied. In some of the more archaic members they can still be used for gliding, whereas in more derived members like the perchloraven they can only be used anymore for social displays and balancing. This leaves only their single front-leg (formerly an arm) as an organ for locomotion.

This anatomy is obviously quite awkward and fragile, which makes it perhaps no wonder why these organisms are rare and only found in environments that lack competition or predators. The perchlorate deserts are obviously just such a place. Surrounded by kilometres of toxic plains and dust, the thermally heated brine pools which the perchloraven inhabits are isolated from the rest of Mars almost perfectly. Here it can awkwardly hop and shuffle around on its leg without fearing any danger.

Much like the caraxor, it can survive here thanks to a high resistance to saltwater and even perchlorate itself, having six nephridia (equivalent to kidneys) instead of the standard four that most other deltadactylians have, a genuine atavism it shares with more archaic onychognaths. Another surprising adaptation revealed by dissection is that the dark dots which colour its back and wings are actually caused by unicellular proteroareozoans which endosymbiotically live inside the organism’s skin. Highly infused with melanin, these microbes show signs of being radiotrophic, much like the fungi discovered in Chernobyl, being able to absorb and use cosmic rays and perhaps even ultraviolet radiation in order to metabolize. If this symbiosis simply exists to protect the perchloraven from the radiation it experiences at higher elevations or if it also gains energy from this relationship is not known. Some of these organisms can be found freely swimming inside the brine pools, so it is likely that the animal acquires them though its diet.

The perchloraven’s main method of feeding, filtering the briny water for small organisms, is evident by the long baleen-like bristles which grow out of its lower jaw, like the teeth of the bizarre pterosaur Pterodaustro. What the headcrest and attached skinflap are for is less obvious, though it likely serves as some form of social display. Perchloravens mate in pairs and give birth to live young raised in rocky nests. An advantage they have over their aerial cousins is that the loss of flight has made the pelvis much less rigid and narrow, allowing the chicks to be born much better developed. Usually they are able to stand, hop and feed by themselves a day or so after birth.

Why exactly the perchloraven is completely naked instead of having feather-scales like its relatives is a good question. Mainly living in thermally heated pools, it seems like there was no need anymore for insolation, allowing the organism to revert back to a more ectothermic metabolism in order to save energy.

On a zoogeographical note, it is also interesting that there is such a north-south divide between perchloraven and caraxor habitats. It has been proposed that the shrubland habitats which line the equator may prevent either organism from crossing into the other hemisphere, as they cannot feed in these zones and would also have to face predators which they have no natural defence against (Watzlawick 2114). What speaks against this is of course the fact that the caraxor can fly.

References:

• Watzlawick, Paul: Wide-scale niche partitioning across Mars, in: Journal of Xenobiology, 189, 2114, p. 310 – 377.

Khonsu and Letox

Ortholitha are a rather minor group of antitrematans, with many, such as the zhor, being primitive, slow-crawling, straight-coned creatures. On the eastern slopes of the giant shield volcano Alba Mons is found an exception to this rule in form of the dove-sized Khonsu. By rolling up their shells into an ammonoid shape, they have become more compact and are capable of walking on erect legs, in some ways converging on their distant nothornithe cousins. But the khonsu’s legs are exoskeletal, like an insect’s.

Khonsu are mountain specialists. Highly developed statocysts in their brain give a heightened sense of balance, while a ball-joint ankle allows for firm, flexible footing across steep slopes. Each chamber in the shell comes with its own air sac, which not only makes the shell lighter but also allows for more efficient respiration in the thin air. To communicate, khonsu can blow air through the whole shell, creating a shrill resonating call that echoes across every cliff of Tharsis. The harsh and long winters they survive by entering a deep sleep, usually sheltered inside caves or under overhangs.

An oddity observed among the khonsu is their behavioural pattern during the summer months. Originally described as cathemeral (meaning their activity follows no clear pattern), it has recently been discovered that their activity actually seems to follow an odd cycle where they are active for four hours and fifteen minutes twice a day (Mess 2339). This does not match up with the daylengths on Mars, but it does with the orbit of its moon Phobos, which flies over Mars so fast that it appears twice a day in the sky. And indeed, khonsu seem to become more active as Phobos rises in the west and go to rest once it sets in the east, twice a day. How, why or even if the moon influences the behaviour of these animals remains to be further investigated.

Khonsu are herbivores which feed on a variety of tough mountain flora, but especially on the aquatic arephytes and fractarians that grow only seasonally during the summer, when the fringes of the glaciers melt and create temporary creeks and ponds. During this time, khonsu become highly territorial of these feeding-, drinking- and mating-spots and are willing to enter fights with each other over them. These fights usually consist of shell-bashing and pushing, though kicking and biting has also been observed. Such fights, as well as the general strains of living in this environment, leave visible marks on the bodies of these animals, which grow by adding a new chamber every year or so to their shell. The older a khonsu is, the more bumpy and irregular its shell tends to look.

It is not uncommon for territorial fights to end poorly for the loser, as they might lose their footing and fall down from great heights or otherwise get seriously injured. Various alpine predators and scavengers therefore observe these fights, waiting to gang up and feed on the victor’s victim. In this case, the spectators happen to be letox, who are members of the Podopterygia. This clade is informally also called “ballousaurs”, after the late W.K. Ballou, to whom these organisms were a special interest. Ballousaurs, descending from one-armed deltadactylians, have developed a unique wing-configuration that has no equal on Earth: They fly with their legs and stand with their one arm. The only thing comparable are the extinct Earth-reptiles Sharovipteryx and Ozimek, but these were merely gliders, whereas Mars’ ballousaurs are fully capable of powered flight, their legs having transformed into pterosaur-like membranous wings. This seems rather ridiculous, though various man-made airplanes follow a similar delta-winged design and have proven quite aerodynamically capable and efficient, so one actually has to wonder why evolution has not produced more such hindwing-fliers throughout our solar system.

The letox certainly come by quite well with their bizarre bodies. These are opportunists who, in short soars, scour the mountainscapes and beyond for small animals and carcasses to feed on. On some occasions they have been observed actually agitating two khonsu into a fight, which implies at least some degree of intelligence. Letox usually live in mated pairs that raise a litter of chicks during summer. The babies are born live, though quite underdeveloped, possibly because the wing-anatomy constrains the size of the pelvic canal. The parents thus care greatly for them in their nests, feeding them until their insulating frilled scales have grown and they are capable of flying on their own. For this purpose, both letox parents are capable of producing a form of “crop milk” that is secreted inside their throat and dripped into the chicks’ mouth.

References:

• Mess, Ingo: Biologie und Naturgeschichte der Ortholithen, Hamburg  2339.