This guest entry was written and illustrated by Troll Man!

As the continents freeze beneath the encroaching glaciers of the poles, ice sheets over a mile high and spreading over millions of square kilometres, the Meridians have remained an isolated oasis in the vast seas of turmoil. In its thirty-five million year seclusion, all manner of unique life-forms have appeared from those that travelled across the ocean blue. Populations of large, terrestrial crustaceans, the only known tribbats to have abandoned the gift of wings, populations of flightless sparrowgulls dominating herbivorous guilds instead of tribbetheres and trunked birds, the only known semi-aquatic dolfinch, and the very last of the land-dwelling burdles. And of course, there are possibly the strangest of the creatures to have crawled free from the sea in a long line of animals that have attempted to lay claim to the land on Serina.

With stalked eyes, sensory tentacles, breathing spiracles, and slimy skin that pulses with undulating colours, these are not vertebrates, but descended from molluscs. These are descendants of estuarine gastropods which once lived as bottom-dwellers in the saline waters around the coasts in warmer days, those which evolved to take in breaths of oxygen straight from the air through vascularized linings of their gill chambers, snarks which managed to transcend the barrier between land and water. What once where fins that cruised beneath the waves now modified into muscular limbs that hauled their bodies across sand and rock. So cut off from the ocean are they now that they would drown if fully submerged for more than an hour, requiring only a thin coat of moisture over their body to survive. How exactly had such changes been undergone? One can merely observe the living species of snarks which inhabit the waters in and around the Meridians to see a rough progression of this leap in evolution, representations of the steps which allowed these snarks to abandon the seas.

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Ancestrally, snarks all possess a remnant of the original ram's horn shell inside of them, a process which is commonplace among gastropods, as the shell is reduced, internalized, and then eventually lost as they evolve from snail to slug. In the snarks the last step did not occur, as it was beneficial for them to retain a stiffening agent for movement through the water without being pushed about, so it developed into a pointed pen similar to the gladius of a squid. Some variant of this condition is present in nearly all snark species, although some (usually smaller benthic or parasitic species) have lost all trace of this pen. The inverse of this condition is segmentation of the pen, which occurs in some benthic species, allowing for greater flexibility without completely sacrificing stiffening of the body. In most species, the individual segmentations have little overall differentiation and are loosely connected by ligaments (illustrated in a simplified diagram, in the leftmost silhouette as I, with a streamertail snark).

The lineage leading up to the first amphibious snarks built upon this segmentation of the pen, as the individual calcareous fragments became more specialized for greater efficiency for certain ecological roles. In early snark species which "walked" on the seabed, they benefited from great muscular strength to their fins and so primitive equivalents to shoulder and pelvic girdles developed to provide greater support for the fins to be used as weight-bearing appendages. The chunks in between became narrower to allow for a greater degree of side-to-side flexion, while further segmentation into the fins themselves created greater tensile strength as attachment points for cartilaginous rods that stiffened them (illustrated in the second silhouette from the left as II, with a charnot).

The first amphibious snarks likely appeared at least fifteen million years prior and occurred through further reinforcement of the rudimentary bones making up the appendages. On land, there is no water medium to help support their weight, and so they must rely entirely on their own muscle strength to lift themselves up. Thus was the development of the first true limb bones, allowing the fins to become primitive legs, although early land snarks relied primarily on the front limbs only to drag themselves ashore, with the hind limbs being more poorly developed and serving mostly as stability to the lower body. Movement outside of the water was likely crude and limited, perhaps only allowing for moments of respite from larger aquatic predators or to birth in isolated pools that would otherwise be unreachable. (illustrated in the silhouette second from the right as III, with a glowgup)

At the current time period, snarks have eventually evolved the endoskeletal support which allows some species to live entirely free of the water. Simple joints have developed in the fins, which now give the snarks the ability to walk with shuffling movement on all four limbs akin to early tetrapods, raising their bodies off the ground rather than simply dragging themselves about. Weight is reduced wherever possible, and other calcareous segments are gradually diminished to the minimum necessary to support the body structure, creating a basic endoskeletal structure akin to a vertebrate. Inversely, the skull is gradually reinforced to protect the vital brain, but has now separated into interconnected plates for greater cranial plasticity. Now only their permeable skin restricts them to moister climes, and they can wander far inland in their foraging (illustrated in the rightmost silhouette as IV, with a prismatic gupgop).

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Charnot (Salmoteuthis ascensus): Although the Meridians themselves do not experience seasons, their effects can still be felt indirectly. For a few weeks a year, an event occurs over the archipelago as creatures from the sea undertake an annual migration to spawn in the sheltered streams and lakes inland. These are not fish, but another of the many snark offshoots, a group once widespread across the world but as many of their continental spawning pools have been destroyed by the drastic falling of sea levels and trapping water in permafrost and glaciers, the last known species of this clade only spawns here at the equator, where the climate never gets cold enough for winter to arrive. Normally dwelling within the southern oceanic waters along the fringes of Eastland in great shoals of bottom-feeders, as winter arrives, they migrate north to breed, travelling many miles to the places they were first born. This is not merely an instinct but a necessary migration regardless, as the season encroachment of the southern glaciers makes the seas inhospitable. Because snarks give live-birth, the actual act of mating occurs at sea, and only females complete the journey all the way back to their birthplace.

This annual event is a great boon to any opportunistic predators of the Meridians. Each foot-long gastropod grows fat in the nutrient-rich polar waters in preparation for their migration and mass spawning, and their soft flesh is relished by all manner of meat-eating animal. Predatory tribbats, sea ravens, pretenguins, larger eelsnakes, and even other snark species pick off thousands of charnots as they enter the archipelago's estuaries. But with many hundreds of thousands of snarks participating in this event, their feeding has little overall effect in their numbers. After all, it is the relative lack of predators in the isolated streams of the Meridians in comparison to the competitive ocean environment that draws them to give birth here. The charnots time their arrival just as the unborn young are close to fully developed, allowing all the females to release the larval snarks at the same time. Each snark can release up to eight per brood, each already close to ten-centimetres in length and fully independent, which in effect immediately overwhelms any possible predators, as the lakes of the Meridians swell with millions of new inhabitants within a month.

Up to ninety-percent of them are killed within the first two months of life, usually by predation or the extreme weather changes, but enough survive this initial period to adapt to their habitat and find shelter among the weeds. The larval snarks are among a minority of snark species for being predominantly vegetarian, feeding mostly on algae, pond scum, and some types of aquatic weeds for the first several months of their life, gradually consuming less vegetation as they mature. The young snarks leave for the sea between a year and eighteen months after birth, when they've reached about half the size of adults, although it usually takes another two to three years before they reach sexual maturity. The adult females which participate in this inland migration do not necessarily die after spawning, and after the act of birth, survivors return to the sea where they can survive to spawn the next year. However, survival rates for females over more than three breeding cycles is low, as repeated periods of stress, predation, and exhaustion take their toll.

The notable aspect of the charnots' migration is how they clamber upstream; unlike salmonids which dramatically leap up waterfalls with furious tail beats, the charnots pass through such obstacles with modified suction cups on the bottom of their fins to stick to the rocks against fast-flowing water and climb vertical waterfalls in a manner analogously comparable to hillstream loaches. Using shuffling, side-to-side movements of its body with its front and back pairs of fins, it crawls against the current, slowly but efficiently. The cuttlebone-like stabilizing internal shell has split into a species of descending segments, giving it both greater rigidity and flexibility between the body anterior and posterior, in effect acting as a simplistic analogue to a vertebrate's spinal column, acting as the stabilizing anchor for taut muscles. This trait likely originated in an oceanic benthic ancestor which benefited from greatly flexibility of the body while foraging on the seabed. It is from this shuffling mechanism that the ability to move free of the water likely developed in the later terrestrial snarks, even though the charnots are an offshoot rather than a direct ancestor. It is nonetheless probable their common ancestor originated as a rapid-dwelling bottom feeder which utilized this method of movement to travel about without being swept away.

Glowgup (Xenospondylus opterognathus): Inhabiting the inland estuaries and coastal bogs of the Meridians is its largest endemic snark species, a transitionary species that does well to encapsulate the link between water-bound and land-living. A pugnacious amphibious predator, the gastropods will haul themselves from the water to bask in the morning light to rejuvenate themselves from the subzero chill that occurs each night. To facilitate this process, they have evolved the ability to survive out of the water for long periods through development of a primitive lung capable of taking in oxygen straight from the air. The gill chambers have been greatly enlarged and divided into four separate chambers, two on each side divided by a muscular valve, the inner linings of which are heavily vascularized to maximum gas exchange. Breathing is unidirectional and accomplished by a pumping motion, with the expansion of the left chambers sucking air in through the left spiracle, the air being pushed through the dividing valve into the right lung chambers, and then the stale air is forced out the right spiracle as new air is sucked in through the left spiracle again, creating a continuous stream of fresh air. Like many aquatic animals which developed similar air-breathing organs, this now means they require periodic breaths to prevent from drowning, as their body has become adapted to the richer and more accessible oxygen from the air.

Pushing itself along using its front fins, it can move slowly on land, relying on its impressive spiny growths and pugnacious attitude to defend itself against terrestrial avian or tribbethere carnivores. The spines on the glowgup's head and dorsal carapace are coated in a potent neurotoxin which it will thrash to spike potential predators with. Glowgups communicate by inflating their rear pair of breathing chambers, which are highly elastic and swell like colourful balloons over the body. Both sexes will use this to ward off predators and intimidate rival snarks, while males will also use them for courtship displays. The glowgups are so named because they produce a luminescent chemical from glands behind the breathing chambers which result in their display sacs producing a flashing neon light show as they inflate. This makes the males clearly visible from a distance when displaying in the dim twilight hours when their courtship dances will be especially prominent. Males hold themselves above the waterline to best attract the attention of females, the inflation of their air sacs creating low audible hums; although glowgups do not have ears and cannot "hear" as most land animals can, they can still detect the vibrations it sends through the water.

Males are vibrantly coloured and nearly twice the mass of females, and use this mass to fight one another over territorial and mating rights. Fights are clumsy but often brutal, as their soft fins and fleshy skin is slashed and ripped by the sharp spines and jagged mandibles of their opponent. Although injuries may be savage, they're generally superficial, as they heal quickly from even severe wounds such as the loss of a fin, provided the animal remains relatively healthy for the period following the incident. Fights occur most commonly during the breeding period of the species, which occurs shortly after the annual migration of the charnots, when the glowgups have grown fat feeding off of their smaller snark brethren and have enough energy to spare for a few weeks. Congregations of males full of reproductive hormones inevitably come into frequent conflict with one another, which has the effect of proving their strength and vigour to any females watching. The greater danger comes afterwards, as exhausted males after extended fighting, courtship, and repeated matings make easy targets for predatory eelsnakes, giant tribbats, and sea ravens.

Females swim upriver to release their young as a strategy to prevent predation from numerous predators, including cannibalism, as adult glowgups will eat smaller members of their species if they catch them. Adults primarily consume slow-moving, hard-shelled animals, such as other snails, large crustaceans, bivalves, and benthic fish, with broad, crushing mandibles to crack through any tough armour plating. Full-grown glowgups are generally slow-moving animals, shuffling along the bottom with just their front fins to uncover prey, but otherwise mostly sedentary. Juvenile glowgups tend to be more agile and mobile, and have a more generalist diet, snapping at small fish and aquatic insects, and sometimes even consuming small wading birds, if they can catch them. Only the juveniles retain the tetrapod-like shuffling movement by moving upon all four fins, which they can do in order to move from one body of water to another, or to capture small insects near the shore. Adult glowgups, at between four and six feet in length and up to forty-five kilograms, are a bit too heavy for regular movement outside of the water. Although this bulk does come to their advantage when they use their hardened, spiny shell to crack through the ice that forms over the water in the freezing night.

Gupgop (Ranalimax sp.): Ambling curiously across the costal beaches and windswept grassy estuaries are one of the most fascinating oddities of the Meridian archipelago, a unique evolutionary marvel that, as of yet, has not appeared anywhere else. Trundling about on four flipper-like appendages mounted on moist-skinned round bodies, these are the gastropod descendants of the aquatic snarks, but which have taken the monumental ecological leap from water to land, requiring now only a thin sheet of moisture across its skin to survive. With the fine sea spray and early morning fog supplying all the humidity it needs to survive, these snarks never need to return to the water (recall that snarks give live birth, and therefore, unlike most Earth amphibians, do not need to spawn in water). Young hatch as miniatures of their parents fully capable of walking moments after birth. Waxy uric secretions over its skin reduce evaporation, while also helping the gupgops to resist the cold, which can reach twenty centigrade below zero every night. As cold-blooded animals, gupgops retreat to underground burrows or dig into soft earth each evening to shelter from the subzero night, emerging as the warmth of the sun stirs them from their state of daily torpor. Rows of ridged skin on the underside of their appendages and body provide ample traction as they shuffle about like tiny, stalk-eyed pinnipeds. The frog-like mollusks are a common sight foraging along the coast of the isle, feeding primarily off of shore-dwelling insects and crustaceans, which are in no short supply, allowing for a radiation of a number of species of varying sizes and forms which inhabit the archipelago.

The main challenge out of the water is not the ability to breathe air (which, in fact, has appeared more than once among snarks), but the structural integrity necessary to hold one's body form out of the water. And so, over millions of years, a strengthened endoskeletal system developed within the gupgop's ancestors and continues to be refined. The first step was the early fetal development towards undoing torsion, a process which occurred in the ancestral gastropod, but has since been lost to varying degrees in several groups, where the body folds over itself so that the anus settles above the head and the nervous system entwines with itself. In snarks, partial detorsion has occurred, recreating the parallel nerve system present in the initial embryonic stages (a condition known as "euthyneury"). Primitive spinal cord equivalents have developed from segmentation and modification of the ancestral gladius, with further extensions into the limbs creating greater muscular support for the fins into modified legs. This is coupled by extremely specialized and repurposed extensions of the radula's "teeth" into a spiny girdle that run parallel on the sides of the body, somewhat like ribs. And so the gupgops are capable of retain their rounded shape out of the water despite lacking an external shell which other many land gastropods use to support themselves.

The gupgops are so named for the grunting sound they can emit when threatened; like all gastropods, they lack ears, and can't actually hear the sounds they themselves make. During courtship displays, these sounds do emit vibrations through the ground that the snarks can detect using their sensory tentacles, which helps the animals locate one another more easily (and listen for possibly approaching predators at that), it's mainly a byproduct of inflating their display sacs. As can be expected, gupgops are capable walkers but not capable runners, and must utilize other forms of defence. Most species are in some form toxic, deriving poisons from a species of noxious coastal isopod which proliferates on the Meridian beaches (that in turn derive their toxicity from a type of scum-like alga that carpets the rocks along the tideline, the same type which is also grazed by a species of tidal snail that the puffbirds derive their own poison from).

The speckled gupgop (R. corporosus), weighing up to one kilogram, is the largest species of gupgop, and is capable of defending itself with vicious bites of its scissor-like mandibles, which it enhances with venomous secretions from glands near the base which run down through grooves of its jaws. Threat displays using its display sacs and loud grunting are ample warning before it shoots out its defensive mandibles, which can eject near its body length in distance to snap at enemies. This venom is not potent, but the painful and prolonged swelling certainly makes a lasting negative impression on anything bitten by it. Because it can rely on merely the strength of its bite more than its toxicity, it consumes less of the toxic isopod than other species, and is capable of consuming moderately sized crabs and crayfish whole using its elastic, extendable pharynx (its mandibles are used only for defensive biting and play little role in prey capture), with their shells digested through chitinase enzymes. Swallowing food items whole, its mandibles are almost entirely defensively used and play little role in prey capture. Other species of gupgop, being smaller and lacking the great jaw strength provided by the speckled gupgop's size, make do with less direct defensive strategies.

The prismatic gupgop (R. gemmoides), which only reaches around two-hundred grams, has intensely distasteful skin secretions which it advertises with a variety of bright colours, which seem to fill the entire visible spectrum of a rainbow. The species comes in a variety of patterns and colours and are a delightful sight as they forage near the tideline in the day. Newborns are a fairly uniform grey, but as they mature they develop into varying different markings and hues depending on genetics, specific diet, climate conditions, and habitat (they also retain an ability to change the shade of their skin possessed by almost all snarks, usually depending on the temperature), although the overall message to predators remains the same. The diversity and plasticity of colour morphs likely originates from when populations were divided across the archipelago roughly one million years ago; when the different islands rejoined one another as sea levels fell, these populations intermingled, creating a wide variety of possible skin tones. Although most predators don't bother with them, some sea ravens have learned to flip them on their stomach and tear into the non-toxic organs and internal flesh to safely consume them. If threatened by such a predator, the gupgops are capable of springing away a short distance by curling their tails underneath their body and pushing off, although it's a desperation defence because they run out of energy rather quickly (although somewhat frog-like in appearance, they cannot actually hop). However, since the amount of consumable meat in each gupgop is relatively meagre compared to the effort, so these only represent a minor threat to the snarks. Young gupgops are commonly preyed upon by the sparrowgull puffbirds, which are unaffected by their toxins, although adults are generally too large to be threatened by them.