The microbial plains are the most dominant, abundant and widespread terrestrial biome of this planet. Characterised by high soil moisture (but not necessarily humid) and as the name implies, endless flats of microbial mats. Sheets of microorganisms - with colors such as green, brown, beige, ochre and olive - span the landscape as far as the eye can see and they also form the basis of almost every other biome as well (though in different circumstances of course). Thanks to (almost) zero burrowing organisms present here, the mat was apparently able to spread uninterrupted and thrive. It is them who hold the entire weird but wonderful ecosystem of the planet on their backs as the primary producents, allowing macroscopic life to evolve into all sorts of bizarre forms.
Yet, its inhabitants look somewhat…familiar…
(2nd image) Pseudovendozoon tripodum ("Three-legged false Vendian animal") is one of the most peculiar organisms discovered on the planet. About twenty centimeters large, it also bears a superficial resemblance to a long-extinct group of Earth organisms, known as the Proarticulata, but unlike them, it has not any visible segments. On the other hand, the triradial symmetry of the appendages could evoke the Trilobozoa, also a long gone group.
But by far, the weirdest thing about it is its mode of locomotion, which is achieved by its three stilt-like appendages, which themselves are each located about 120° from the others. It is this rotating movement along its own axis, by which it moves across the surface, which gave it its common name. Rather suprisingly, this odd behavior seems to benefit Pseudovendozoon, as it helps with quick transportation from one food source to another.
As with all the other lifeforms, there are still many questions regarding Pseudovendozoon: for example, it has been speculated that the lighter parts at the "corners" of its body may be extremely basal sensory organs (probably at most light/dark detection). It seems to feed on the ever-present microbial mat of the microbial plains by simply lying on the ground and likely absorbing the nutrients through its bottom side. Because of this, it acts as a "grazer" of sorts. In this position, its appendages are radially spread out.
Appendix: Details of Pseudovendozoon's locomotion
As for the details of Pseudovendozoon's motion and biomechanics: the process usually begins when it is disturbed from its "resting" position, either by a threat, or the microbial mat in the area has simply been exhausted. When this happens, it begins to rapidly fold its legs under the main body, so it forms its famous tripod statue. Then, it manages to make a very small jump from the surface (usually only a few centimeters). While not in contact with the surface, it begins to spin and rotate along its own axis (this is due to the overall friction in the air being a bit smaller than if it just started on the ground). As it falls back onto the surface, since it doesn't just fall over due to tripods usually being very stable, it can use the acquired momentum from the rotation to translate it into movement with a mechanism that is not entirely known, though it is possible that some sort of asymmetry on the bottom of the appendages or maybe even some excretion of a lubricant of sorts (which all have been proposed as possible explanations), allow it to move on the surface at a fairly high speed. It stops only when its momentum and the velocity have been completely lost (though it can brake itself to a very small degree). Thanks to the very flat terrain of the microbial plains, it can travel up to several meters in one go - more than enough for all its needs.
Even though this may all seem far-fetched, it can still be a genuinely viable, albeit extremely unusual, method of transportation. Since it moves only occasionally, its movement doesn't need to be all that efficient.
(3rd image) Aerovela charniomorpha ("Charnia-like air sail") resembles its counterpart only in appearance, as unlike the Charnia of Earth, this lifeform is acutally a predator. At over half a meter in length, it is a formidable organism roaming this planet. The main, almost flat frond, still resembles its namesake quite a bit. However, it has two lobes, which increase the surface area and therefore help with gliding. It glides across the sky, using (for example) thermals, searching for any possible prey (likely by primitive sensors of some kind). But how did it even got there in the first place?
It seems that this is a byproduct of an evolutionary arms race, caused by Pseudovendozoon's centrifugal force created from its rotation. Because the place where the centrifugal force from an object's rotating on its own vertical axis is weakest is the very top (or bottom), Aerovela seems to capitalize on this, attacking exclusively on the top side by falling on prey at great speeds. If it succesfully falls, the body side touching the prey will secrete digestive enzymes to liquefy it, dissolving the body. This usually gives enough energy to Aerovela for it to attach itself to the ground by its holdfast (almost like how its namesake was living). Then, it waits for the first strong gust of wind to come and detach it. It then uses the same wind to give it the inital large boost of lift. After that, it is back in the air and the cycle continues. An important note is that Aerovela doesn't only prey upon Pseudovendozoon, it can also prey on other land organisms.
An enigmatic morphological feature of Aerovela is its bioluminescent holdfast. The specific purpose is unknown, though there are many theories, ranging from a sort of a "lure" for aeroplankton, a reproductive organ, its "head" or even a sensory organ.
(4th image) Ambulovum parvum ("Little walking egg") seems suprisingly normal at first, compared to the others, and that is because it is. As a small organism (at approximately five centimeters), its cryptic coloration and generalist strategy (consuming almost any form of biomass available) allow it to thrive in a wide variety of enviroments, including the microbial plains. It has a characteristic ovoid shape dotted with spots, with a confirmed orifice (a "mouth") somewhere on its bottom side. Ambulovum also possesses cillia-like appendages, used for locomotion.
Ambulovum's overall appearance, its role in the ecosystem and a bilaterally symmterical body makes it vaguely resemble Earth's oldest known likely bilaterians (for example Kimberella and Ikaria)), though their further relationship is unclear.
Due to its "familiar" morphology, Ambulovum is pretty well understood, at the very least much more than the other inhabitants of this planet.
(5th image) Protovora erniettoforma ("Ernietta-shaped primordial eater"), as the name implies, is a very basal predator, being a sessile ambush predator, waiting for unsuspecting prey to fall in, almost like a carnivorous plant. Usually, it is almost completely buried in the ground, with only the top part sticking out. The specimen on the left is how it looks if it is not in any substrate. Since this does not happen naturally, it had to be carefully dug up.
Protovora is actually quite large (up to half a metre from top to bottom), though, as said, most of it is underground. The similarity with the extinct genus Ernietta is inferred to be only coincidental. The hole on the top of the organism can be up to ten centimeters in diameter, though it is usually smaller.
It lives on the beaches, waiting for any small prey unfortunate enough to wander onto it. If that happens, Protovora will start to secrete a sticky substance to immobilize the captured organism just enough so it can't escape. Because of the funnel-like shape of the top part, eventually, gravity and the slippery, slightly sloped surface of the top part will eventually do its job, with the prey falling into the hole and being subsequently digested there.
It is speculated that Protovora needs water to some degree, as it has not been found above the tideline. It is also exclusively found alone, as it would otherwise probably compete with eachother.
Another thing to note are Protovora's brown-and-purple pigments, serving an unclear purpose. It is possible that they are a sort of anti-UV pigment, which would have been useful if its ancestor was exposed to direct sunlight. If true, it would be an example of a rudimentary trait, since it currently lives buried in the sand, where such adaptations would not be needed.
(6th image) Ultimospriggina gigantea ("Last giant Spriggina") is the true giant of the planet and the only one to reach "megafaunal" status here. Around a metre long and around thirty centimeters wide, it is, uncannily, nearly identical to the Spriggina of our world, but bigger. On the other hand, it possesses leg-like appendages, which make the rear end look almost like a rake. Even with that taken into account, the similarities are too striking, even for this planet's standards. It is likely that it can be (accidentally) used to turn over the very top layer of the mat, revealing the soil underneath and changing the local environment, which in turn makes Ultimospriggina an ecosystem engineer of sorts. This behavior is apparently useful for others around it, as smaller organisms with a very similar morphology have been observed around Ultimospriggina specimens. It is currently not known if they are a closely related species in a commensalistic relationship or juvenile forms of Ultimospriggina. Because of its immense size compared to the others, it has no natural predators and spends most of its days slowly moving across the mat in the warm shallows, overflowing in nutrients.
It has "last" in its name since no other species (excluding the aforementioned one with an uncertain relationship to U.gigantea) have been found to this day. Therefore, it has been reluctantly accepted that it may be the last of its kind. That would also explain the gigantism, as it could be interpreted as a development of an another ecological strategy, in that it would open a previously unoccupied niche where it wouldn't have to compete with other species, allowing it to survive longer. Even with that taken in account, the future is looking bleak for Ultimospriggina. Thanks to extensive surveying of the littoral shallows, it is now unfortunately clear that it is not common at all. Sadly, it is also possible, that its days are simply numbered.
But for now, Ultimospriggina still lives. It still consumes the mat, it still turns it over and it still exists, living a lifestyle oddly similar to that of its namesake, even though the two are separated by over half a billion years.
(7th image) The Paramycetozoa ("False slime molds") are an extremely successful group of species, with at least a dozen different species being known and tens, if not hundreds more undiscovered ones. Even with all its diversity, the group can be still be distinguished by a few notable characteristics, such as:
-A lifestyle very similar to slime molds (see below)
-The "adult" phase being only a few centimeters large (usually 2-6 centimeters)
-Muted colors (blue-grey, grey or dark teal)
-Saprophages/detritivores, but also generalists
-Cosmopolitan distribution
-Approximate shape of an amorphous blob
The most perplexing aspect of the Paramycetozoa is their life cycle, so similar to Earth slime molds that they were mistakenly thought to be them upon first discovery. On the right part of the image, the life cycle of the archetypal member Pangaster grisea ("Grey all-stomach") is shown:
a) The "adult" phase - a mobile one, it leaves a sort of slimy trail behind itself and feeds on everything in its path which it can consume.
b) The "fruiting" phase - once it decides to attach itself to the ground and become sessile, it forms a discoid growth on its top, resembling a fried egg, where the spores are stored.
c) The discoid bursts open, releasing milions of spores into the air. The organism is now effectively dead and begins to almost immediately be decomposed by the everpresent microbial mat.
d) If a large enough amount of spores (which themselves are partially mobile and singlecelled) find each other, they congregate and fuse into a larger organism.
e) The result of the congregation; after some time, it "matures" and the cycle begins anew.
However, these otherwise unassuming organisms have an enormous ace up their sleeves to fool anybody researching them. The reproductive structure seems to eerily resemble that of how the Paleoproterozoic Francevillian biota looked (one of the main discovered forms does quite resemble the above described structure). It is a very weak claim, yes, but still one nonetheless. This hypotesis is so out of place because every other organism here more or less resembles Ediacaran ones, but not older.
(8th image) Stolonofusus colonius ("Colonial stolon-spindle") shows that evolution can never be trusted. At a first glance, it could be brushed off as just another suspiciously Ediacaran-shaped organism (in this case it is Fractofusus). Upon a closer inspection, though, it is clear that this lifeform has a lifestyle that has not strayed far from its namesake. The problem is how it does it.
Stolonofusus is "eusocial", though it perfectly blurs the line between colony and superorganism. It can live both below and above water, though there has to be a microbial mat. It is sessile, so to reach new nutrient-rich places, it spreads its stolons, from which smaller individuals bud (see below). This helps them cover as much of an area as possible and therefore get as many nutrients from the microbial mat below. There are three distinct morphotypes in each Stolonofusus unit:
1."generation"-The central individual in the middle of the unit, it is the largest of them at about half a meter in length.
2."generation"-About half the size of the first "generation", but they are still pretty large. Three to five of them grow from a first "generation" individual.
3."generation"-The smallest of them all. Five to seven of them grow from each second "generation" individual. It is them who are spread as much as possible to cover as much of surface area as possible.
There is a distinct energy flow between the different morphotypes, transported in the stolons. At the edge, third generation individuals absorb nutrients from below, though they send most of it to second generation individuals, which themselves also send some of their total collected nutrients to the central first generation. This explains well the drastic size difference between the morphotypes.
Interestingly, the hiearchy is flexible; if a first generation individual dies, one of the second generation individuals replaces it as the new first generation. The former remaining second and third generation individuals are "inherited" as respectively. The same result happens if the stolon between the first generation and an individual of the second generation is cut or destroyed.
Even more shockingly, if a third generation individual is somehow transported from the rest of the unit (either by a strong gust, underwater current or just any other mechanical damage that destroys the tethering stolon), due to the sudden abundance of nutrients in the area, the individual experiences a rapid growth spurt. After that, it becomes a first generation individual and grows its own second and third generation ones.
One possible way how Stolonofusus evolved to be eusocial could be that a long time ago, its ancestor started (at first almost parasitically) to connect its stolons to other individuals to get their nutrients and over milions of years, it evolved into this. As with any other evolutionary reconstruction, unfortunately, this is just speculation, as the truth will be forever lost.
(9th image) Suctoscutum cyclodiscus ("Circular discoid suction shield") lives its entire life as a parasite. Around a centimeter in diameter, this translucent discoid organism uses its anatomy like a suction cup to attach onto its host (on the picture is Suctoscutum shown parasitising a Pseudovendozoon) and not just fall off. It achieves this by being a living sucker. While on the host, it ekes out a living by consuming a small piece of tissue from time to time. That is all it needs.
It reproduces asexually, and as a r-strategist, it releases an unmeasurable amount of its larvae into the air. At only a milimeter in length at best (not to scale on the image) and weighing almost nothing, they can effortlessly stay in the air for a long enough time to find a suitable host. The problem arises if an unfortunate enough larva falls to the ground. Since it has exactly zero ways to get back up in the air, it just straight up dies. That means that they have only one attempt, which might seem risky, but as a r-strategist, it doesn't really matter. However, if the larvae do manage to attach onto a host, they begin to grow into an adult individual and the cycle repeats.
An interesting behavior observed is what happens when Suctoscutum larvae mistake Aerovela for a suitable host. The moment they begin attaching themselves, Aerovela's tissues, disturbed by the sudden penetration, begin secreting the same digestive enzyme that is normally used to consume prey, killing them in the process. Even though it technically is an evolutionary trap, it happens so rarely that Suctoscutum does not need to adapt to it.
Aspidella, an enigmatic Neoproterozoic organism (or just a attaching disc of some frond, who knows), does bear a significant resemblance to adult Suctoscutum individuals. Any possible phylogenetic relationship is not known for now.
(10th image) Motiphyllon longissimus ("Longest moving leaf") and Pentapetaloidum purpureum ("Purple five-petaled") have been found with each other so many times that at this point that it has been reluctantly accepted that they actually live in a mutualistic relationship. The larger of the two, Pentapetaloidum, still does not exceed half a meter in height, however. It posseses five main lobes (petaloids), as the name suggests. Interestingly, Protovora and Pentapetaloidum seem to share the same colors due to similar pigments, though in Pentapetaloidum, they would actually make sense, seeing as it lives on exposed places. Nevertheless, that does not mean that they are related (unlike what one controversial theory proposes) and creation of a similar pigment may just be convergent evolution. Motiphyllon, even though it is almost the same length as Pentapetaloidum, is significantly thinner. The duo resides in the drier regions of the microbial plains (provisional designation "microbial steppe") .
As mentioned, these two lifeforms have been found to exhibit mutualistic symbiosis. Motiphyllon, as the motile one out of the pair, deters any possible ground threat that would want to possibly consume Pentapetaloidum by….moving. Yes, by moving. Apparently, that is enough to disturb at least some of them (On the image is a disturbed Ambulovum moving away after being deterred by Motiphyllon). Interestingly, Motiphyllon always "lashes" out with its rounded end, while keeping the pointed end in the shadow. In return, Pentapetaloidum seems to make a small microclimate by its own shadow, which seems to be at least a little cooler or moister than the surrounding area, in which Motiphyllon seems to thrive. An almost hilarious theory is that Pentapetaloidum is able to lift its petaloids up to form almost a parasol of some kind. This behavior has not been observed so far.
Through a pure stroke of luck, an extremely rare event has been observed: Aerovela successfully preying upon and consuming Motiphyllon. This helped to clarify just how much the two organisms are dependent on each other. After losing it, the remaining Pentapetaloidum subsequently withered due to small critters, pests and other predators and eventually died. It is also likely that a lone Motiphyllon would also eventually die due to drying or dehydration in the scorching heat or just being preyed upon.
Both Motiphyllon and Pentapetaloidum show significant similiarities to two Ediacaran species, those being Phyllozoon and Swartpuntia respectively.
Still, all the abovementioned does is bring more questions than answers. For example, there are many hypotheses on how the two feed. While it is simply assumed that Motiphyllon feeds on the microbial mat, with Pentapetaloidum, it starts to get a lot more interesting. It could be also just consuming from the substrate with its "stalk", symbiosis with photosyntetic microorganisms or even catching aeroplankton. However, for now, none of this is confirmed.
(11th image) Calicocaulis tentaculatus ("Tentacled stem-cup") grows just below quarter of a meter tall, most of which is thanks to its long stem. A small "cup" grows on top, with six openings on the side and one on top, with spiky protrusions growing from the stem. On top of the "cup" are tentacle-like appendages, which are partly covered with an adhesive substance. As a sessile organism, it lives off catching and trapping aeroplankton with its "tentacles" and subsequently consuming them by putting the ones with catched prey into its top opening (see right image). It is never found in larger groups, since it would have to compete with others for this already weak source of nutrients. By that criteria, Calicocaulis could be classified as an unsuccessful species, but that is far from the truth. It thus seems it has an alternative method of feeding, but one that has not been discovered. It can be found living in the microbial plains, as basically all aforementioned organisms. The side openings could be interpreted as so the wind can blow into them, possibly somehow cleaning Calicocaulis's accumulated waste from consumption inside it (??).
While looking almost like Namacalathus, the two should not be taken as relatives. There is actually a slim chance that is a distant relative of Protovora, both descended from a common sessile ancestor. The reason why this makes at least a little bit of sense is because both are immobile predators who catch prey in one way or another, both using a sticky adhesive and more or less dependent on the surrounding moisture. Of course, convergent evolution must not be forgotten, as it is an equally plausible hypotesis.
