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Imagine, now, a camera lowered slowly into this alien sea. Beneath its translucent shell the light, so brightly-reflected on the surface, is dim: and as we descend it eventually becomes pitch black. The shallow seafloor of Marilis is covered by vast icesheets: what remains is the depths of
the open ocean. Marilis, like Earth, has a core of molten metal: this gives it a magnetic field, which retains its atmosphere, and a process of plate tectonics.

We are going to visit one of these plate boundaries, a long north-south line that marks the creation of the eastern plate from beneath the west. Along this line, white-hot lava spills from undersea volcanos, for a brief time illuminating its surroundings before cooling into dark igneous rock. In their light we might be able to glimpse the inhabitants of this alien landscape, in which the pressure of the water above would crush us like tangerines. They are gathered around hydrothermal vents: fissures in the seafloor. Around the clock, boiling-hot water full of dissolved minerals rushes out from underground, mingling into the surrounding ocean and creating strange oases, havens for life.

[All geographical features are up for naming, at one person per feature. Nothing too silly, please.]

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Multicellular life on Marilis is very young: it may have only originated in the last ten thousand years, and has so far not been able to spread beyond a single tectonic ridge. The Marilian fauna is very uniform -- throughout the world our camera-probe would record only three forms of life, all small by our standards. They would seem to us entirely different offshoots from the phylogenetic tree, but they are in fact only aspects of a single species seen at different stages in its life cycle. We will call them Ardans, from ardor (heat) in reference to the warmth of the vents.

(Credit to "A Person" from the evogame Discord for these two great maps.)

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The Motiloid
------------

The first stage we will examine is the Motiloid. Like the other two stages, it is invertebrate. It resembles a seaslug: slow-moving and benthic, travelling on a fleshy pad. At one end of its body it has a toothless mouth, which connects to a digestive tract and anus at the body's other end. Its only senses are touch and a perception of heat, which prevents it from wandering away from the vents. They are formed at around 0.2cm long and grow at a consistent rate over the course of around four Marilian months to a final size of about 0.8cm. Their only food source is the Sessiloids, the next stage of the Ardan life cycle.

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The Sessiloid
--------------------

The Sessiloid is the final stage of an Ardan's life. It is so named because it is sessile, anchored to the seafloor. The motiloid, after its four-month existence, undergoes a metamorphosis: its fleshy pad changes into a holdfast, stabilising the organism against the water currents. Its sensory nerves, no longer necessary, are dissolved: its mouth, digestive tract, and anus are repurposed into a simple filtration system. The sessiloid sucks water into the "mouth", where it is filtered for chemicals in the former digestive tract, and then expelled at the other end. All Ardan stages have a basic suction ability: they can use muscles to widen their digestive tract whilst keeping the "anus" closed, thus drawing water in through the "mouth". Starting at around 0.8cm, the sessiloid can grow to roughly 2.5cm. The sessiloids are consumed by the motiloids.
The motiloid wanders blindly until it encounters a sessiloid, which it identifies by touch; it then uses its mouth in a repetitive twisting-jerking motion, together with suction, to rip off pieces and swallow them.

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The Pelagoid
-------------------

When a motiloid consumes a sessiloid, the genetic material of the sessiloid is extracted and stored in the motiloid's body. Around once a month, the motiloid combines the sessiloid's genes with its own in an internal sexual reproductive process. The motiloid will then, over a period of several days, produce small buds. These buds detach, becoming the Pelagoids: small (around 0.2 cm long) and free-swimming, they travel through the water using a pumping system. They suck the water in through the "mouth" and expel it through the "anus" in regular bursts, producing forward motion. The pelagoid has not yet developed the sense of touch possessed by the motiloid; it has only the basic heat-sense that stops it from leaving the
vent line. It will wander around the vents randomly for around a week, ensuring that the genetic material of the Ardan is distributed, before eventually settling on the ground and metamorphosing into a motiloid.

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Rules
-----

1. If possible use a good-quality paint program like Paint.Net or Gimp. Turn off aliasing and save as .png.
2. You are allowed to radiate a single organism as much as you like, but not progress it more than twice in a row.
3. Don't change an organism too much in a single evolution. That's up to your discretion but I'll step in if it's far too much.

In this thread:

1. Organisms cannot leave the vent line.
2. Organisms cannot grow to more than two metres long.
3. Organisms cannot become sentient.

Let's make this a good one.

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>>3569373
due to a simple genetic mutation, some of the sessiloids gain a second "mouth" when they reach their final life stage. for the most part this doesn't show up in the previous two, appearing only as a small dot next to their other mouth currently.

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>>3569373
A new species emerges, denoted by a difference in the structure of their sessiloids; the new sessiloids are taller, and have begun using the surrounding heat to their advantage - hot water is sucked into the inner cavity, where it begins ascending, giving off it's heat and inciting a thermally catalyzed chemical reaction on the way out.

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>>3569370
>>3569375
The Gliders are denoted by their advanced Pelagoid stage, fitted with a pair of simple flaps on it's top and bottom that allow it to steer left and right. In their Motiloid stage, the creatures rotate 90 degrees clockwise, the two flaps now at their sides and used to glide short distances using the surrounding water currents.

Oh, please put a size on new evolutions: I figured people would take the images off >>3569378 but it's also fine to just write the size on anywhere.

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>>3569370
A new mutation has given some Motiloids a second sense; with their new lateral line organs, they now have some ability to detect water flows and pressure, letting them sense movement around themselves.

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>>3569830
The Hunters use their new sense to their advantage, locating other motiloids and sucking their innards out with their new powerful mouths.

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>>3569378
>>3569395
The Dualoid's secondary digestive system is repurposed into a primitive "gill" in it's pelagoid and motiloid stages. To increase the efficiency of oxygen absorption through this organ, the cells of the creature now produce hemoglobin.

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>>3570644
The dualoid begins to develop large growths at the top of their bodies, which through a sort of chemical cocktail 'smells' better to their motiloid phase. they can regrow these growths, albeit rather slowly, and thanks to this the Dualoid can survive multiple feedings from a motiloid.

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>>3569400
Taking advantage of their greater energy budget, some tall sessiloids develop a thin lining of precipitated minerals in their outer layers. This shell, while providing some protection from over-grazing by motiloids, is more valuable in its role of helping to trap the heat of the siphoned water and improve the efficiency of their thermotrophy.

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>>3570826
Trace amounts of the mineral shell are consumed along with the sessiloid's flesh, allowing the motiloids to develop shells of their own for defense against >>3570640.

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>>3570640
the bodies of some Hunter motiloids become thin and serpentine, allowing for a greater range of motion and speed as well as the ability to swim. Their pelagoid stage also slims and grows larger, again allowing them to move faster, yet strangely their sessiloid stage doesn't change very much at all.

>>3570826
I like your style

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>>3571482
Hunter motiloids develop a protrusion of flesh at the tip of their tails. At the same time as the motiloid enters its reproductive phase, the protrusion produces a chemical signal inducing other hunter motiloids to consume it. As such, the sessiloid stage is no longer required for hunter reproduction, and the species is now neotenous.

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>>3571580
The pelagoids of the hunters develop lateral lines as well, in order to make sure their hungry elders don't eat them.

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>>3572485
The Spiral Motiloids have an elongated digestive tract that allows them to better digest nutrients

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>>3570918

Chimney Sessiloids develop a sort of 'fruit' containing genetic data. This allows them to survive the attacks of motiloids by saving their main bodies from destruction while still allowing them to reproduce

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>>3572541
The secondary tube now has an internal chamber of it's own, this one lined by musculature rather than thermotrophic cells, used to pump more water inside the body.
The fruits move closer to the bottom to be more accessible to the motiloids.

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>>3572537
A powerful digestive tract meant that many of the consumed motiloid's cells would be destroyed, leading to a drop in birth rates due to the difficulty of reproduction.
To restore their reproductive capabilities, a "throat sack" was developed, a secondary stomach used solely for absorbing reproductive cells of consumed peers.

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>>3574134
the spiral hunter's pelagoid stage has developed to become parasitic, getting nutrients from the various stages of other Ardans as they produce spiral hunter motiloids. this has also caused the pelagoid to shrink slightly in size.

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>>3569373
Ardan Floatoid
---------------------
Some Sessiloids don't make the cut, their holdfast too weak. After loosing their purchase, they float near vents, tumbling around in the currents and blindly filtering in the direction of heat to not stray away from them.
At least it keeps them from many a kind of Motiloid that crawl along the seafloor, both allowing to reach bigger size(up to 5cm), but also hampering the ability to pass on the weak holdfast trait reliably.

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>>3574548
>>3569404
The Floatoids interbreed with the Gliders, as their gliding membranes allow them to more easily reach the floating sessiloids. As those who can glide better are more likely to eat and reproduce, individuals with bigger membranes are selected for.

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Life on Marilis has already evolved in several different directions, creating new and varied groups of organisms. The most basal Ardans, which are grouped in the monotypic genus Ardanima, have given rise to five different families: Velovilidae, the gliders; Hypocaustidae, the chimneys; Duosidae, the dualoids; Venatoridae, the hunters; and finally Adscensoridae, the floatoids.

All of the species that have evolved on Marilis in this period are still extant, but the vent communities have changed as some have been rarer and others more common. The original Ardans, Ardanima, have declined as they are being outcompeted in every stage of their lifecycle by their more derived descendants. For the same reason the most basal species of Hypocaustum and Duos are also becoming rarer, as are all the species in Provenator and Venator.

The most numerous species in most ecosystems are the most derived species of Hypocaustum -- this is especially seen in sessiloid and motiloid faunas, where their armour gives them an edge. However, their pelagoids are still preyed upon by Venatorids. The advanced species of Duosids are quite successful, and the Velivolids. The Velivolids in particular have one of the best rates of pelagoid survival due to their "fin" adaptation. The Adscensorids, having evolved only recently, are rare; but they are alone in the niche of floating filter-feeders.

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>>3574610
The Glider-floaters develop small fotosensitive bulbs at their fronts, allowing them to be slightly better at avoiding hunters - though not by much, due to the dark conditions. The "eyes" are receptive mostly to infrared.

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>>3574928

Now that both the pelagoid and motiloid stages are both free-swimming, they also cease being distinct stages and fuse into one stage. The free-floating Sessiloids now have tendrils that allow them to cling to other free-floating Sessiloids, forming sessiloid colonies.

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>>3572673

Fruit sessiloids are characterized by the ring of fruits at their base. These fruits are full of chemicals that stimulates a Motiloid's ability to produce Pelagoids.

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>>3570735

The motiloids of the Dualoid strain have mouths that migrate to the top of their heads, to allow them to better reach the Sessiloid stage's fruits.

Incidentally, this also makes them incompatible with the OTHER Sessiloid that makes fruits...

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>>3574510
some spiral hunters have begun defending >>3576598 colonies from other predators. Although this might not seem logical, the inner parts of a floater colony are ideal places for their parasitic pelagoids to feed, safe from other predators who may eat them. to better maneuver around and inside colonies, the motiloid spiral hunters have developed large fins on the sides of their body, giving them a greater range of motion.

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>>3571482
As they are outcompeted by more advanced descendants, the original Hunters turn to parasitism instead. When the Motiloid finds a suitable host, instead of eating it it will latch onto it tightly with it's suction cup-like mouth, and metamorphosize into the Sessiloid. If however the host already has a parasitic Sessiloid, the Motiloid will instead grab onto the Sessiloid and suck out a small amount of flesh, impregnating itself and soon giving birth to dozens of Pelagoids, beginning the cycle anew. The mother does not survive the birth process.

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>>3574928
Some Gliders develop rigid formations towards the front of their fins, used to assist during the initial liftoff in swimming.

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>>3576709

A cluster of nerves evolves to further help Gliders control the bony protrusions

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>>3576675
Spiral Hunters develop larger wingflaps for more mobility. A second, smaller set of wingflaps develops on their tails

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>>3576607
The Shellbearers have developed a way to protect their young against the hunters: their children are no longer born as pelagoids, now bearing a closer resemblance to motiloids(although unable to reproduce until maturation) and sticking close to their parent, following it and hiding under it when danger presents iself.

>>3570826
Those Chimney Sessiloids that haven't developed fruit have instead opted towards producing spores; not only does this allow them to spread their genes over wider distances, but it also bypasses that nasty "needs to be eaten to breed" restriction. However, since the species's Motiloids don't have access to the calcium contained in fruits, they don't develop shells until becoming Sessiloids, and as such face increased predation from Spiral Hunters, keeping the population in check. As an upside, they also no longer have a genetic incentive towards being picky with their food and eat basically every non-armored, non-flying Sessiloid species with impunity.

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>>3576926
Forgot picture

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>>3576675
The Biped Hunters have a bifurcated tail, making them worse at swimming yet much better at climbing the lattices of Floater Sessiloids. As their pelagoids no longer lead an active lifestyle, they assume a more rotund form, capable only of latching onto a Floater and sucking on it until maturation.
Only one pelagoid is produced after pregnancy; while normally this would mean the amount of dead hunters and newly born hunters would be equal, in practice thanks to the high population density in the Floater lattices a dead hunter is shared between many peers, impregnating each one and boosting the population by five or six pelagoids, which have a reasonably high chance of surviving to adulthood.

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>>3576767
With how many Hunters now live in the Floater lattices, it's getting kinda crowded. Luckily, the Hunter-Hunters now keep the populations of other hunters in check, preying on them with their new beaks, derived from the clamps of their pelagoid stages.

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EVENT
-----------

Over the past millennium, geological activity along the tectonic line has sharply increased. Earthquakes have become frequent and severe: these shake sessiloids from their anchors, where strong currents pull them away from the vents to the barren ocean beyond, proving fatal. Rocks are often dislodged from the sides of the vents, crushing motiloids and sessiloids as they fall down the slopes. There has also been an increase in volcanism: periodic lava flows annihilate entire communities for living around the volcanoes. The effect of all this is that great pressure is placed on benthic fauna, leading to a swathe of extinctions and a loss of diversity.

The original Ardans, Ardanima, are made extinct. The hypocaustids, with a lifecycle centred on their ground-dwelling motiloid and sessiloid stages, are hit hard: the most basal four species of Hypocaustum are eradicated, as well as the more derived H. multifructus and Pollimax, leaving only H. bifidum and the spore-producing Granartifex. The duosids are also severely affected -- only the most derived species, D. altosculum, survives. The outlook for nectonic (free-swimming) communities living in the water column, though, is brighter. The venatorids suffer limited damage. The basal genera Provenator and Venator go extinct due to the reduction in slow-moving Ardanimaform pelagoids, their primary food source. However, the most derived species of Neovenator, N. collosaccus, survives, as do the more advanced genera Celegnathus and Unatus. The other main part of the nektorial ecosystem are the velivolids / adscensorids, which have combined into the new family Altavidae. The titular genera Velivolum and Adscensor become extinct, their benthic sessiloids proving too much of a weakness; the same is true for most of the species of Altavis, although the derived species A. intellegentis struggles on. However, the genus Triflagellum, having evolved a nectonic sessiloid stage, continues to thrive without competition.

The high volcanism also has a somewhat positive effect: the water within about a hundred kilometres of the tectonic line is warmed by around five to fifteen degrees depending on distance. The ocean water also becomes much richer in minerals. These two improvements increase the range of habitat for nectonic ecosystems, allowing for greater energy to pass through the trophic levels.

>>3583928
Oh, the parasitic venatorid Paravenator >>3576684 also survives. Forgot to mention.

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>>3572673

The Poison sessiloid possess poisonous fruits due to the exotic minerals that permeate the waters. Only motiloids who can survive eating the poisonous fruits go on to become Poison Sessiloids, making each subsequent generation more poisonous and at the same time, more immune to its own poison.

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>>3578902

The Supreme Hunter motiloids have extended beaks that they use for slicing apart their prey. The action allows them to extract more energy at once by allowing them to digest smaller parts. Their pelagoid stage also gain expanded pincers

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>>3576684

Parasitic sessiloids lose their ability to filter feed as they become fully parasitic. They instead now derive sustenance from the food that their host consumes.

In return, they pump their host with growth hormone that allows their host to grow to disgusting, unnatural sizes. Those with several parasitic sessiloids become nothing more than gigantic, moving tumours.

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>>3576927

Chimney Sessiloids now have specialized organs used for the production of spores. The spores now have a mildly irritant effect that its earlier stages are immune to.

Chimney sessiloids tend to congregate, producing massive spore clouds where they do.

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>>3576611
With the high concentrations of novel pollutants now present in the water, breathing has proven difficult to the Dualoids. Only those with more advanced methods of oxygen absorption survive: their primitive breathing cavities have over time expanded and gained additional slits on the sides, used to expel stray particles that become lodged in the organ. The neck of the Motiloid extends as well, keeping it's head from the soot-covered seafloor.

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>>3576598
The Floater Sessiloids have lost their midsection, not only reducing the amount of surface area a parasite could latch onto but also making their bodies akin to parachutes, using the currents of hot water below them to keep themselves afloat.

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>>3576740
To protect the sensitive nerves, a ring made of the same rigid, cellulose-like material as the finbones is developed. It also aids in anchoring the fins to the rest of the body.

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>>3572673

Bifidums gain a more complicated method of filtering due to the number of pollutants in the water. They now store sand filtered from the water inside their main body and expel it as an irritant when their main body is being preyed on.

Some of them are lucky enough to be growing near >>3585369, giving them access to that species spores as an irritant.

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>>3585386
To escape the irritants, those Bifidum Motiloids living near >>3585369 develop shells that envelop a much larger portion of their bodies, as well as begin keeping their Pelagoids under these shells. However, their mobility is impaired significantly.

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>>3585355
When threatened, the Poison Bifidum is able to shoot out a small dose of it's poison - a deadly weapon when many of it's enemies still practice osmosis. In Motiloids, the poison is discharged through the anus, but in Sessiloids the secondary tube is the weapon of choice. The shell around it's bend is now thinner and the muscles that once lined it are no longer atrophied during maturation, offering a somewhat limited degree of motion to this defensive mechanism.

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>>3585385


The next stage in evolution for the Intellegentis is more of what it already have. More nerves for finer control, and more bones to protect those nerves.

In particular, they have a pseudospine along their backs that turns into a whip-like limb as a sessiloid.

Some of the intelligentis, however, delay their metamorphosis of the sessiloid by collecting >>3585365, allowing them to grow to truly massive proportions.

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>>3585395

Bifidum motiloids develop pseudopods that allow them to move unimpeded even with their large shells. These limbs are immune to the irritating properties of air pollutants.

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>>3585403
The pseudospines are now present on both sides of the creature, allowing the Sessiloid to have one more whip.

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>>3585403
A different breed of Glider is the Fisher, known for it's heterotrophic Sessiloid stage. It has been afflicted by a mutation that causes it to retain it's digestive tract instead of repurposing it into a filter as it matures, and now uses it's pseudospine to catch unsuspecting motiloids and drop them into it's mouth opening.

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The volcanic activity on Marilis has caused significant change in its faunal communities. Before, there was a fairly uniform biota of basal, mainly benthic Ardans forming similar ecosystems. However, the faunal turnover has produced a number of more advanced organisms, specialised to thrive in different areas of the environment. There are now four distinct biozones, in which different species hold sway. Let's first reacquaint ourselves with the phylogenetic history of our groups with updated charts.

Altavidae

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>>3585636
Hypocaustidae

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>>3585639
Duosidae

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>>3585640
And finally, Venatoridae

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>>3585644
The four zones of life on modern Marilis are the Volcanic, Inner, Outer, and Upper Zones. The volcanic zone is closest to the volcanos; the Inner and Outer are further out, and the Upper Zone is the water column. The further away from the volcanic zone, the cooler the water and the lower the amount of dissolved minerals (as a general rule, not taking into account the presence of local vents.)

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>>3585648
* Thanks to A Person for that map

In the Volcanic Zone, intense tectonic activity makes the environment hostile to life: there are frequent earthquakes, rockfalls, surges of water current, and even lava flows. It does, however, play host to a sparse ecosystem. The single benthic motiloid and sessiloid is Granartifex placidus, a relatively basal hypocaustid. Compared to its more derived competitors, it has a simple motiloid and sessiloid stage: this allows it to mature more quickly and thus have a better chance of reproducing before being destroyed. Its shift in reproduction from pelagoids to spores, and its removal of the need for the motiloid to feed on the sessiloid, reduces the reproduction period and increases the number of young in a generation. Their defenceless motiloids, though, are preyed on by the basal venatorid Neovenator collosaccus; and both are in time parasitised by Paravenator anchora.

Where the Volcanic Zone is lethal because of geologic weaponry, the Inner Zone attacks with biological poisons. This is the home of the toxic hypocaustids Toxiturris funeredo and T. granimimus, and also of Granifex aegrae which pumps irritating spores into the water. The only other organism that is able to exist here is the duosid Longicollus macronaris, which is able to reject poisons from its respiratory system.

The Outer Zone, in comparison, is a gentle realm where many species coexist. The chemosynthetic Hypocaustum bifidum can be found here, and all species of its descendent genus Trioturris. Beware, though: the advanced altavid Scutica is also resident here, defending itself with a barbed whip (or two), and its predatory descendant Motivorax. The more basal altavids Altavis catafractus and A. intellegentis are also found here, as well as the duosid Longicollus altosculum. Fulfilling a predatory role is again Neovenator, this time being parasitised not by P. anchora but its hormone-pumping descendant P. amplificator.

Finally, the Upper Zone, the three-dimensional water column. Here float interlocking colonies of the sessiloids of Triflagelli duoformarum and T. adstrictus, and between them dash their winged pelagoids. The Triflagelli, though, are consumed and even conserved by the advanced venatorid genera Celegnathus and Unatus, that live cheek-to-brow in these sea-cities. And, of course, the predators are themselves prey to the familiar Paravenator.

>>3585686
(I neglected an important point here: Celegnathus polypos and C. imperator are preying on other venatorids, ie. Celegnathus hirudo, defensor, and cascabatia as well as Unatus.)

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>>3585360
The Hunter-hunter Pelagoids develop a long, spear-like proboscis between their pincers, allowing them to burrow deeper into their hosts akin to ticks, through cyclic motion of the pincers, making them significantly harder to remove and less likely to be eaten, as their bodies can now be concealed almost entirely within the host. At maturation, the proboscis breaks off, the wound left behind quickly metamorphosizing into the new mouth.

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>>3585398

Stinger granimimus have, as their name suggests, a stinger which helps them inject their prey with deadly toxins.

Their favorite prey are the Longicollus Macronaris, and any of the species from the Volcanic Zone that wander into the Inner Zone

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>>3585372

The Macronaris continue to select for ever-taller specimens. Two filters are raised above the Macronaris's mouth that allow filtration of water while keeping the irritants out. Meanwhile, their Sessiloid stage simply grows taller.

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>>3574134

The Neovenator Collosacus' reproductive gene containing tail loops back and fuses with its throat.

The throat sack now contains egg cells that are fertilized by another Collosaccus' tail.

Their Pelagoid stages gestate entirely within the mother's throat sac, which bursts when they are ready to be born. Each pregnancy can have 4-5 Pelagoids. The mother does not typically survive the violent birth and is eaten by the pelagoids.

>>3587810
Forgot to mention, Neovenator Collosacus are essentially hermaphrodites and reproduce by shoving their tail into another Collosacus' throat sac

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>>3576927

The Granartifex Placidus adopts a two-layered structure, with its spore-producing organ relocating to the middle of its mouth.

It now filters spores from the waters, sending it to a birthing chamber in its center, where it gestates its pelagoids. They don't leave until they've become motiloids.

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>>3576767

The Celegnathus Defensors now live up to their name with several tough plates that can't be pierced by >>3587686 This protects them from predation by the Hunter hunters.

@Op

Can we just quote the latest phylogenetic tree instead of tracking down posts where the creatures were originally posted?

It's getting hard to track down posts when so many of the venatorids are similar to each other.

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>>3576684

The Vent Sessiloids colonize the volcanic vents. They are covered in specialized pigment spots that convert the heat energy coming from the volcanic vents into energy.

>>3587826
If that makes it easier for you, go ahead.

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>>3587810
The Cyclic Hunter's tail elongates, now used as a "lasso" of sorts that the creature can catch prey with. Incidentally, this adaptation also makes it more likely to survive childbirth, as the larger tail's biomass is sometimes enough to last the creature until it regrows it's head, and it's violent trashing when left without a nervous system's control can repel predators.

>>3587820
The Motiloid of the Granartifex Placidus gains a trait similar to it's Sessiolid - it's anus is now ingrown, emerging from it's mouth.
The Sessiloid itself gains a slightly thicker shell.

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>>3587895
forgot picture

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>>3587800
The Sessiloid gains another vent just like the Pelagoid and Motiloid, the latter of which has begun "standing up" to reach the fruit.

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>>3587900

The Macronaris adopt a tripedal body style, allowing them to reach taller heights. The Sessiloids also become taller and adopt a radially symmetrical series of tubes.

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>>3587896

The Placidus gain large fleshy flaps covered in a sticky substance. When a motiloid or pelagoid approaches, the flaps curl inward, allowing the sessiloid to digest it.

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>>3587686
Some of these Celegnathus undergo a neotenic mutation, retaining their prosbosces: instead of the mouth forming from the point where the prosboscis breaks off, it now grows beneath it. The prosboscis now has a hollow tube inside it, connected to several holes near its point. The feeding strategy is now to stab the prey deeply and then use the holes to suck out their internal organs, leaving only skin behind.

This species migrates out of the Upper Zone into the Outer Zone. Its hunting method is to swim low above sea floor, picking off benthic motiloids. Longicollus altosculum is the easiest prey, but due to their uncommonness the typical diet of these Celegnathids is mainly Altavis catafractus and intellegentis. There is a level of competition with Neovenator, and this usually resolves with Neovenators shifting to a more pelagivorous diet.

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>>3585636

The Sessiloid stage of the Scutica telocaris now becomes free-swimming like its other stages. Now that it's no longer sessile, the name of the stage becomes Duoflagelloid.

It swims by paddling with both of its pseudospines. Some additional nerves grow in order to coordinate them better.

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>>3585636

Triflagelli adstrictus becomes completely flat and can have anywhere from 3 to 5 actual flagella.


They will congregate, forming large spheroids containing their pelagoids and the pelagoids of venatorids, almost becoming self-contained biomes.

Upon reaching sufficient size, a colony of them will split into two globes, much like a macro version of mitosis.

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>>3585403
In the areas where the symbiosis between Altavis catafractus and Paravenator amplificator was most common, it is integrated further into their lifestyles. This new Altavis species grows a fleshy holdfast that grabs the Paravenator, making it less likely to be dislodged by a predator or a strong current. The hormones from the Paravenator cause the Altavis motiloid to grow up to five times its normal size, making it into a massive grazer feeding on sessiloids that are now often smaller than itself. Its protofins atrophy away, though it retains its neck armour. It loses the ability to morph into a sessiloid and it now fulfils that part of its lifecycle by consuming the sessiloids of the other Altavis species.

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>>3587900
The pelagoids of these Longicollus adopt pelagivory, increasing the size of their "mouth" and using it to suck in and digest other pelagoids with a precocious digestive system.

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>>3585381
Another branch of Triflagelli adstrictus simply increases the numbers of arms in its sessiloid. This creates much more cover in the colonies for their pelagoids to hide from venatorids.

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>>3587900
Some Longicollus have switched the location of their mouth and one of their breathing organs, this gives them a longer reach.

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>>3587890
Some of these Neovenators change to an ambush strategy in order to hunt the very mobile duoflagelloids of Scutica >>3590479. They hide themselves in crevices, bunching up their tails with the aid of elastic tendons, and then suddenly allow them to spring out. With luck, this hits the duoflagelloid with a powerful flow and stuns them, allowing them to caught and consumed by the Neovenator.

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>>3590479
As the Duoflagelloids are much bigger than Motiloids, they are understandably difficult for them to eat. Because of this, those Duoflagelloids that trailed an edible strip of flesh behind them were the ones most likely to reproduce. However, those strips are not very nutritious, so the Motiloids now have to turn to predation on other species to survive, aided by their superior senses and mobility and competing with both the neovenator and the celegnathus, as well as the occasional motivorax.

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>>3590513
The upper tendrils are now covered in hairs that catch edible particles diffused in the water. After a tendril collects enough particles, it will be brought to the mouth in order to consume them.
Also, the mouth recedes into the body as the "neck" area was previously rather susceptible to parasites.

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>>3590487

The fleshy holdfasts on either side of the Altavis develops into secondary mouths that lead to their own 'stomachs'.

However, instead of leading the Paravenator Aplificator to their deaths, these are instead devoid of stomach acid and instead are used to allow the amplificator to inject its hormones deeper into the Altavis's body.

It's not uncommon for entire generations of the Paravenator Amplificator to live their entire lives inside one of the Altavis's stomachs.

When the Altavis matures from a Pelagoid to a Motiloid, it will typically acquire amplificators from its parent, who will regurgitate amplificators into its newly matured young.

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>>3590514

The Giraffe's long neck is now supported by a long, strong muscle to provide support.

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>>3590565

The sessiloid now exhibits countless long tendrils that end in hairs. They will typically hang themselves on the bottom side of sessiloid colonies, catching diffuse particles with their hairs, then ejecting the digested particles into the colony.

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Updated cladograms!

Hypocaustidae and Duosidae

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>>3593956
Altavidae and Venatoridae

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>>3593959
A slight correction: the venatorid Incendiphagus is descended from Paravenator anchora, not the more derived Paravenator amplificator.

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A shift in the temperature, acidity, and mineralisation of the ocean water, coming on top of existing predation and competition pressure, results in the extinction of many basal species. Those that remain are shown in their ecosystems food webs in this diagram.

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>>3587823
The Defensor's plates grow in size, making it even harder to damage for the other Celegnathus, as they are armed solely with piercing weaponry. The Defensor itself is armed with a toothy upper jaw instead, scraping layers of skin off of the sluggish Floaters into it's maw, sometimes taking a parasitic pelagoid along with it's meal.

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>>3599162

The Cassis' long neglected pelagoid stage gains a protective shell as well. For the motiloid stage, it gains a large lower jaw, all the better for scooping up prey.

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>>3590539
The Duoflagelloid stage of Scutica Telocaris gains flaps for better mobility. Also, their eyes become more complex, being a set of photosensitive cells in a spherical shape with an aperture controlled by nerves.

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>>3593959
Ouroboros Catapulta transforms into a characteristic crescent shape that allows it to fire its waves in front of itself.

Furthermore, its reproductive organ fully fuses with its lower jaw.

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>>3599207
The Pelagoids now spend much longer in-utero, emerging with a more developed body that is better suited to evading capture by predators.
The juvenile is capable of both swimming and traversing terrain, folding it's tail under itself and using it to jump.