Puraeus

Although Venus has no trees, even it has more arboreal organisms than Mars, most of them living in the floating jungles of the upper atmosphere. Martians meanwhile have not much to climb on except for rocks, boulders, mountains and maybe a few tall shrubs here and there. The degrading climate has stopped supporting the growth of tree-like organisms millions of years ago. The only exception is the region of the Hellas Basin, but even here the scale-trees and tube-trees grow only sparsely, making the region resemble an open savannah more than forest. As such there are not many organisms specially adapted to dwell on them.

One of the few savannah-dwellers that can actually be called arboreal is a relic from an earlier time. The puraeus is one of the last remaining flagrobrachians. These are one of the groups which make up the insect-like phylum Aspiderma, to which also belong the wadjets. The relationship is immediately apparent, with the six lens-eyes, large head-plates and even little external gills, which look like they could be the archaic precursors to wings. Yet this animal cannot fly, but instead slithers and hangs between the branches of the scale-trees like a serpent. Neither are flagrobrachians the ancestors of wadjets, they are their own group that, as fossils show, made their way independently out of the vanished Martian oceans onto land.

Their most distinguishing feature are their mandibles, which have been repurposed into a pair of raptorial arms from which sprout long, prehensile tendrils. The puraeus is an ambush-predator, which lies in wait hanging from trees, ensnaring any smaller creatures which might climb or fly by, such as nekhbets. As the puraeus can no longer utilize its mandibles to kill and chew its prey, its jawless mouth has evolved a syringe-like spur, hidden underneath the headshield. With this it injects venom into its prey, as well as a strong acid, which digests it from the inside and allows the predator to simply suck it dry, like a spider.

The venom is also useful as a defensive weapon, as the puraeus can fall prey to various flying creatures such as ballousaurs. It is usually not strong enough to kill the attacker, but based on the behaviour of those bitten, it appears to cause a lot of stinging pain. Of course, no astronaut has ever volunteered to test that hypothesis themselves.

Puraeus also nest in trees, usually in holes beneath the bark. There they also raise their young. Once two puraeus have mated, only the impregnated partner will care for the offspring, but does so quite dutifully until they are old enough to hunt themselves. Until then it will usually feed them with regurgitated juices.

Yateveo

Winter in the tundras of Mars is desolate and hostile. The flora enters a near-death state, only protected by anti-freezing fluids. Small animals that can only crawl or are sessile enter a deep state of hibernation, hidden underground. The animals with legs wander north to the warmer shrublands. But there is one exception.

The yateveo is a wanderstalk which stays in the frozen wasteland, even though it should be able to migrate like its relatives. But it does not like using its legs much, instead preferring to stay in one spot for most of its life. Yet, despite its sessile nature, it is the most skilled carnivore among its clade. Most wanderstalks capture their wadjet prey by lying valve-open like a venus fly trap, waiting for a hapless victim to land on them, perhaps attracted by pheromones. Once the prey lands, tentacles ensnare it and the valves clap shut. Yateveo does not have that patience.

Its natural weapons are two highly modified arms which can shoot out sharp needles attached to silk-like strings. Biological harpoons. In principle they function somewhat like a multicellular version of the nematocysts of jellyfish. When not in use, the needles sit inside a pressurised chamber, ready to dart out. When attacking, the chamber opens a little, pushing all the air out and the needle with it. Once it has pierced its prey, muscular action retracts the string, reeling the harpoon in. How this organ may have evolved remains a mystery. If it can also regrow if severed is also an open question.

What is known is that this artillery is so efficient compared to its relatives that the yateveo rarely has to change location but can spend most of its life in a single place and simply snipe poor little fliers out of the air. This also means that it can easily accrue enough storage of nutrients and fat inside its stalk and legs that it can easily sleep through the winter, thanks to its low metabolism.

However, there is one occasion where yateveo do get up and walk and that is during the thawed-red summer months where they try to find a mate. During these times, they can rarely be observed hunting on foot, which is quite an odd sight to behold. Combining eyesight, leg-movement and aiming speaks for coordination-skills that are uncharacteristically high for such an otherwise primitive organism.

Wanderstalk

Striding on its roots

There comes the Wanderstalk,

not wearing any boots.

It does not like to talk

It is not yet a plant

And neither a zoon

It trotted on top of the sand

Which it liked to grow on.

Striding on its roots

Thereon, as stiff as a balk,

not wearing any boots,

there goes the Wanderstalk.

- Müslüm Zohra, Martian Poems, 2285.

When first approached, wanderstalks may appear to an unwary astronaut to be ordinary species of shellubim. They are seemingly sessile organisms, or “planimals”, firmly anchored into the ground by long stalks. Their soft body is protected by a hinged shell, out of which they extend eye-stalks and leaf-like fleshy wings, which photosynthesize enough to fuel the organism’s resting metabolism. But when startled, these organisms have a trick up their sleeves that their sessile cousins lack. They can simply emerge out of the dirt and walk away on crustaceous legs. Wanderstalks are in fact not shellubim, but terrestrial relatives of the amstiels. Most fossil and genetic evidence suggests that they represent a second invasion of land by this basal grade of antitrematans, with endosymbiotic photosynthesis in both being a case of convergent evolution.

And it seems the wanderstalks may be slowly winning their race to land, for they are far more widespread and numerous than the shellubim. They can be found in nearly all habitats, though are especially common in the southern highlands and other elevated regions, whereas shellubim are only common in the northern lowlands and the Hellas Basin. The most likely explanation lies in the atmospheric development of Mars. Shellubim are sessile as adults and reproduce through pollen-like gametes and small mobile larvae which fly or even freely float in the air as aeroplankton. As the fossil record of these organisms suggests, this used to be a very successful strategy early in the planet’s history due to its low gravity, but as global air pressure declined, staying airborne became increasingly difficult, hindering reproduction and also leading to a large decline in the aeroplanktonic ecosystem that adult shellubim fed on. Thus, they are now largely restricted to lowland regions, where air pressure remains higher than average. Wanderstalks meanwhile remain mobile and grounded their entire life and reproduce directly. Much like their aquatic relatives, two individuals simply walk up to each other and mate. The developing young are then either deposited as eggs into the ground or are carried inside the parent’s body, but in both cases come into the world as miniature adults able to walk and live on their own. It is likely that the even more numerous skolex evolved their particular mode of reproduction for similar reasons.

Wanderstalks also do not rely on microscopic aeroplankton to feed. Their eye-stalks double as muscular tentacles, in some of the larger species are strong enough to break an astronaut’s finger (yes, this is based on someone's personal experience). Through a combination of bright colours, foul stenches, sucrose secretions and/or even venom, wanderstalks attract, grab and kill smaller wadjets, which they feed on inside a closed shell, using a pair of mandibles comparable to what is seen in the zhor. In at least one reported case, a yateveo was even observed feeding on the proboscis of a poor ptannu (a tundraic species of bennu) that had unwisely stuck its beak into the wanderstalk’s shell.

Wanderstalks also have the advantage of migrating towards suitable habitats when necessary. Most of the ones living in the tundraic southern highlands in fact do, following the wadjet swarms into the northern shrublands and the Hellas Savannah when winter makes the South nearly uninhabitable. The intriguing thing about this is that they migrate in remarkably straight paths, suggesting they have an innate sense of distinguishing between north and south. How they do this is not yet known. Mars has no global magnetic field which these organisms could exploit in the same way as migrating birds do on Earth, only localized hotspots created by magnetized ancient crust.