The Early Hyperpelagene

As the Hyperpelagene Epoch began, Atmos’s oceans experienced a significant transformation driven by a sharp rise in oxygen levels—an increase of approximately 20%. This surge in available oxygen had profound effects on marine life, enabling organisms to grow larger, sustain more active metabolisms, and evolve increasingly complex body structures. With greater oxygen intake, many species developed enhanced musculature, more efficient circulatory systems, and in some cases, advanced methods of locomotion that allowed them to pursue prey or escape predators with newfound speed and agility.

This influx of oxygen also reshaped the ecological landscape by opening up new niches, accelerating evolutionary arms races, and increasing the efficiency of energy transfer through marine food webs. Predators grew larger and more specialized, while prey species developed new strategies for defense, from reinforced body structures to sophisticated forms of camouflage and behavioral adaptations. Sessile and slow-moving organisms, once dominant in the oceans, faced growing competition from more mobile and active creatures, pushing many toward further innovation or decline.

The biosphere of Atmos entered a period of rapid diversification, as life adapted to these new opportunities and challenges. The oceans teemed with an unprecedented variety of organisms, forming ecosystems more dynamic and interconnected than ever before. This evolutionary explosion laid the foundation for the Hyperpelagene Epoch, an era that would be defined by its vast, teeming seas, filled with creatures of newfound complexity and size, marking one of the most dramatic shifts in the history of life on Atmos.

The Miruverms

The Mystaceverms

Magnustachis

Magnustachis (Great Mustaches) is a lineage of mystaceverms that have grown significantly by the early Hyperpelagene, with the largest species reaching up to one or two meters in length. This increase in size coincides with the rising oxygen levels and expanding benthic ecosystems, allowing them to establish themselves as dominant members of the seafloor community. Their five ancestral body segments have split into seven, granting them increased flexibility and control over their movement.

The mustaches surrounding their mouths, already a hallmark of their lineage, have become even more pronounced and specialized. These thick, muscular tendrils now serve a variety of functions: probing through sediment, grasping food items, and even acting as defensive feelers to detect approaching threats. Some species use them to scrape biofilm off lithoflora, while others employ them as sensory whiskers to detect the faintest vibrations of potential prey.

Despite their larger size, magnustachids are far from invincible. Larger velicatiplods, predatory vorms, and other benthic hunters pose a constant danger. To counter these threats, some magnustachid species have evolved thicker hides, while others have taken to burrowing more frequently, using their tendrils to rapidly dig themselves into the sediment when threatened. A few have even developed cryptic coloration, blending seamlessly into the ocean floor.

Coclestachis

Coclestachis (Shelled Mustaches) is a clade of mystacheverms which has taken a different approach to survival compared to their magnustachid cousins. Rather than growing larger or more mobile, or relying on burrowing or camouflage, these creatures have evolved a thick, protective shell that encases much of their segmented bodies, serving as a formidable defense against the many predators of the Hyperpelagene seas. 

Unlike the flexible, soft-bodied mystaceverms that preceded them, coclestachids possess a rigid exoskeletal covering, which varies wildly in shape and texture depending on the species. Some have developed smooth, dome-like carapaces, resembling the stones and coral-like formations of the ocean floor, while others have evolved spiny or ridged shells, making them difficult for predators to grasp or swallow.

Despite their heavy armor, coclestachids have not abandoned the sensory and feeding adaptations of their ancestors. Their mustaches remain highly developed, protruding from openings in the shell to feel their surroundings, detect vibrations, and locate food. Some species use their mustaches as trap-like sensory nets, waving them in the currents to capture small drifting organisms, while others use them to probe into crevices for buried prey.

The Veloverms

Cyanovorms

Cyanovormis (Blue-Eating Vorms) represent an important evolutionary step in the rise of the vorms, a lineage of streamlined velovorms that have become the dominant swimmers of Atmos’s oceans. As their name suggests, cyanovorms are cyanovores, specializing in grazing on the vast mats of cyanophytes that proliferate throughout the seas. 

Unlike their more primitive relatives, cyanovorms have evolved a nearly fusiform body shape, allowing for efficient and sustained swimming. Their elongated forms, paired with powerful undulating movement, make them agile foragers, capable of covering large distances in search of cyanophyte blooms. Their mouths have developed specialized scraping structures to strip cyanophytes from surfaces, with most possessing two large teeth protruding from the top and bottom of their mouths. 

With their growing ecological success, vorms as a whole are poised to become the dominant marine vertebrates of Atmos. They are the closest equivalent to fish on this world—streamlined, efficient swimmers that will radiate into an immense variety of forms. 

Ostiverms

Ostivermis (Mouth Worms) is a lineage of veloverms which has abandoned active hunting or grazing in favor of an enormous filter-feeding lifestyle. Over millions of years, these creatures have evolved massive, gaping mouths, capable of engulfing vast quantities of plankton-rich water with each rhythmic pulse of their segmented bodies.  

With such an abundant food source available, ostiverms have grown to be the largest organism the planet has ever seen. Some species stretch to lengths rivaling entire shoals of smaller vorms. Their once-agile veloverm ancestors relied on speed, but ostiverms move with slow, undulating grace, drifting through nutrient-rich currents with minimal energy expenditure. 

However, ostiverms are not invincible. Bloodsucking sugoplod parasites cling to their soft skin, siphoning nutrients from their circulatory systems, while mordeverms, Atmos’s first true macropredators, prowl in coordinated packs, targeting vulnerable individuals. As the apex filter-feeders of the Hyperpelagene, ostiverms shape entire marine ecosystems, fueling the evolution of specialized symbionts, scavengers, and hunters.

Mordevermis

The arrival of Mordevermis (Biting Worms) marks the beginning of macropredation on Atmos—heralding the rise of large, powerful hunters capable of taking down even larger prey. In contrast to the passive filter-feeders and scavengers that once dominated the seas, these relentless predators actively chase, capture, and subdue their targets. 

The mordeverm's sleek, torpedo-like bodies resemble those of Earth’s dolphins and ichthyosaurs, an example of convergent evolution—the tendency for organisms in similar environments to evolve analogous body plans. This hydrodynamic form minimizes drag, allowing mordeverms to reach high speeds with minimal energy expenditure, while their side fins, dorsal fin, and finned tail provide superior maneuverability and control. Their long, narrow mouths are lined with rows of thin, razor-sharp teeth, designed for slicing into soft flesh and gripping struggling prey. These teeth, much like those of Earth’s sharks, frequently break off in their victims, ensuring a continuous supply of fresh, sharp replacements. 

Mordeverms exhibit complex pack-hunting behavior, with agile virifers leading the chase, coordinating to weaken prey before delivering the final blow. Unlike many solitary predators, they return with food to sustain the larger, slower matrifers, which in turn tend to the juvenilafers—ensuring the survival of the next generation of Atmos’s first apex predators.

The Dumboverms

Alacricoronis

Alacricoronis (Spirited Crowns) is a lineage of relatively small but highly agile dumbocrowns that have adapted to an active predatory lifestyle. Like their relatives, these creatures rely on bursts of speed and sharp maneuverability, which alacricrowns use to chase down fast-moving prey. Their primary hunting grounds are the bustling lithoflora reefs and shallow coastal shoals, where they weave through dense thickets of aquatic growth, ambushing small vorms and other swift marine creatures that inhabit these waters. 

The pronged fin at the end of their bodies functions as a rudder for precise control over their rapid swimming patterns. This adaptation, combined with their powerful undulating propulsion, allows them to make sharp turns and sudden accelerations, giving them an edge in the chaotic and competitive reef environment. Their large, forward-facing eyes provide excellent depth perception, helping them track their prey with precision.

Laruacoronis

Laruacoronis (Ghost Crowns) is a delicate and ethereal lineage of dumbocrowns that have adapted to a vertical swimming posture, much like Earth’s seahorses. Unlike their larger and more robust relatives, these tiny creatures drift through the water with an almost spectral grace, their translucent bodies rendering them nearly invisible against the shifting light of the open ocean. This transparency serves as both a defense mechanism against predators and a means of ambushing microscopic prey, which they capture with sudden, precise movements. 

One of their most striking features is their elaborate, flowing crowns—thick, membranous structures that extend from their heads and backs like delicate veils. Though these crowns still serve the same propulsive function as they do in other dumbocrowns, helping laruacrowns maneuver through the water with subtle undulations, they have also been dramatically exaggerated by sexual selection. Individuals with the largest, most ornate crowns tend to be the most successful in attracting mates, leading to increasingly elaborate and visually striking forms over generations. This dual-purpose adaptation allows laruacrowns to maintain their graceful, drifting locomotion while also using their crowns as a display of fitness and vitality in their complex courtship rituals. 

Laruacrowns are relatively social compared to other dumbocrowns, often congregating in loose, drifting schools where they engage in intricate courtship dances. Their slow, vertical movements and tendency to sway gently with the currents make them resemble floating wisps of living silk, adding to their ghostly appearance. While they are not particularly active hunters, they feed by hovering near dense clusters of plankton and small cyanophyte grazers, using their quick, darting strikes to snatch up meals, their heads propelling towards their prey by their propulsive crowns.

The Segniverms

Spathuvermis (Legged Worms) is a lineage of segniverms that have diverged from their tiny, plankton-feeding ancestors. Unlike their predecessors, which relied mostly on undulating movements and passive drifting, spathuverms have further adapted their three pairs of leg-like appendages to swimming. These flexible, fin-like structures provide them with enhanced maneuverability, allowing them to move with more precision than their undulatory relatives.  

Despite this adaptation, spathuverms struggle to establish themselves in the increasingly competitive pelagic ecosystem of the Hyperpelagene. Faster and more efficient swimmers like veloverms dominate the open ocean, their streamlined bodies and rapid movements making them superior hunters and filter-feeders. The natastachids, with their long, rippling mustaches and benthic camouflage, have secured their own specialized niche, leaving little room for spathuverms in midwater zones. Even dumbocrowns, with their powerful jet propulsion and efficient filter-feeding, have carved out a dominant niche in the pelagic ecosystem, further marginalizing the struggling spathuverms. 

As a result, most species of spathuverms are restricted to marginal environments, where competition is less intense. Some have adapted to deep-sea habitats, where slower movement and low-energy lifestyles are advantageous. Others have transitioned to estuarine or brackish waters, where fluctuating conditions make it difficult for their more specialized competitors to thrive. However, their inability to fully exploit the vast pelagic realm has left them as a remnant lineage, overshadowed by the more dominant swimmers of the Hyperpelagene seas.

This form of defensive mimicry provides comiverms with a crucial advantage: by resembling harmless cyanophytes, they can avoid the attention of visual predators that hunt by shape and movement. Their rhythmic, swaying motion further enhances the illusion, making them nearly indistinguishable from the surrounding mats of cyanocoma. Some species have refined this mimicry even further, developing subtle bioluminescence to imitate the faint glow of certain cyanophytes. 

Despite their disguise, comiverms are not passive drifters. They actively graze on microbial life, filtering out plankton with specialized mouthparts. Some species are even opportunistic, snapping up smaller organisms that mistake them for harmless cyanophytes. In a pelagic environment where segniverms have struggled to compete with the more efficient veloverms, natastachids, and dumbocrowns, the comiverm lineage has survived by becoming masters of deception.

The Pleruplods

The Velicatiplods

One of the most fascinating aspects of their reproductive cycle is the role reversal that occurs between the virifer and matrifer stages. Some individuals who fail to secure mates during their virifer stage may, under certain environmental pressures, delay their transition to matriferhood, instead continuing to roam and compete for extended periods. Others may take on a temporary “helper” role, guarding a relative’s offspring in exchange for access to their territory or the opportunity to reproduce indirectly. This flexible life history strategy allows centuriplod populations to adapt to fluctuating ecological conditions, ensuring their continued survival.

Sugoplods (Sucking Legs) is a lineage of velicatiplod descendants that have developed specialized suction pads on the bottom of their feet, allowing them to cling tightly to rocky surfaces, much like Earth’s tree frogs or clingfish. This adaptation enables them to scale cliffs and other vertical environments where they graze on small cyanophytes and poremorphs, exploiting food sources that are inaccessible to many other creatures. To further enhance their survival, sugoplods have evolved large, camouflaged shells that help them blend seamlessly into the rocky outcrops and lithoflora they inhabit. These shells not only provide passive protection from predators but also act as stabilizers, giving them extra support when adhering to uneven surfaces. 

Remuplodis (Paddle Legs) is a lineage of velicatiplods that have transitioned into an active, pelagic lifestyle. Their twelve legs have evolved into broad, muscular paddles, allowing them to propel themselves efficiently through the open water. Without an internal skeleton, their paddles rely on a combination of muscular contractions and a hydraulic system where fluid is pumped in and out of the limbs—similar to the hemolymph-driven limb movement seen in Earth’s spiders—to generate forceful strokes. 

Their predatory strategy involves using their elongated front pincers to snatch prey from the water column, a method reminiscent of mantis shrimp on Earth. These specialized appendages give them an advantage in capturing fast-moving prey, such as small vorms and pleruplods, but they also face stiff competition from other pelagic hunters, particularly veloverms. To aid in buoyancy and stabilization, remuplods have developed a distinctive adaptation: a hollow, gas-filled horn atop their shells, much like the ammonite shells of Earth’s past. This structure allows them to remain neutrally buoyant, conserving energy as they navigate the currents.  

Despite these adaptations, remuplods struggle to find a secure ecological foothold in the face of fierce competition from veloverms, natastachids, and dumbocrowns. Their niche appears to be one of opportunistic ambush predation—hovering in the midwater, relying on their buoyancy to remain motionless before striking with their long pincers. Unlike the more streamlined, fast-swimming veloverms, remuplods may favor short bursts of movement rather than sustained chases, allowing them to specialize in ambushing slower or more unsuspecting prey in the open ocean. 

The Lutumplods

Moreover, duocrustaplods have developed a unique form of symbiosis with certain species of microscopic fungi and bacteria, which live on the surface of their skins. These microorganisms aid in breaking down the organic matter that the duocrustaplods consume, enriching their diet and providing them with essential nutrients that they might otherwise miss from the seafloor detritus alone. In return, the microorganisms receive shelter and nutrients from the duocrustaplods’ body fluids on their skin. This relationship enhances their ecological role as detritivores, making them key players in the recycling of nutrients in the ocean floor ecosystems. Many species, from small maculovorms to larger mordeverms, prey upon the duocrustaplods regularly. However, their r-selected high reproductive rate and ability to seek refuge in tight spaces help sustain their populations despite heavy predation. 

Herenaceuplodis (Sand Legs), or "Sand Gobblers," is lineage of lutumplods that has adapted to a life spent almost entirely buried in sand. Unlike their shelled ancestors, sand gobblers have completely lost their protective shell, opting instead for a highly flattened body that allows them to blend seamlessly into their sandy environment. Their streamlined shape is perfect for staying close to the substrate while minimizing exposure to predators. 

The head of a sand gobbler is positioned close to the seafloor, where it lies lazily, mouth open, constantly scooping up detritus and other organic matter from the sand. This feeding method allows them to passively collect a wide range of nutrients without expending significant energy. Their sandy coloration offers excellent camouflage, helping them avoid detection by predators as they remain largely hidden beneath the surface. 

Their flattened, disk-shaped bodies are made up of soft, pliable tissue that helps them move with minimal resistance through the sand, enabling them to burrow further down or shift position with ease. The lack of a rigid exoskeleton or endoskeleton means they can contort and shift in ways their shelled ancestors could not, making them more flexible and capable of occupying tighter spaces within the sand. This pliability also aids in their camouflage, as their bodies can subtly conform to the contours of the substrate, making them less noticeable to predators. 

The Magtrogs

Pipantistrogis (Pipantine Eaters), affectionately called “dumplings” due to their plump, rounded appearance, represent a striking divergence from their sessile magtrog ancestors. Unlike their benthic relatives, which remain sessile throughout their maturity, these creatures remain motile throughout their entire lives, never settling onto the seafloor to anchor themselves. Instead, they have embraced a permanently free-swimming existence, retaining the general body plan of juvenilafer pipants while growing larger and more muscular during adulthood. This evolutionary shift has allowed them to occupy a distinct niche, drifting and propelling themselves through the water column in search of food.

Their method of locomotion remains similar to their pipant ancestors, using their eight undulating tentacles to propel themselves with surprising agility. However, instead of eventually settling into a sessile magtroglodyte stage, dumplings reproduce directly within the open ocean, releasing their offspring into the water column where they, too, remain fully mobile for life. Over time, they have developed a more advanced sensory system: the once-simple photosensitive cells that lined their oral region have evolved into a distinct ring of primitive eyes surrounding their large, filter-feeding mouths. This adaptation grants them 360-degree environmental awareness, allowing them to detect movement, changes in light, and potential threats from all directions.

Despite their soft, dumpling-like form, dumplings are active filter feeders, sweeping their tentacles through the water to capture plankton and organic detritus. They have found success in a wide range of environments, from coastal shallows to deeper mesopelagic zones, where they drift in large, slow-moving shoals—ever-hungry clouds of living dumplings floating through the seas. 

The Playtglosses

The platyglosses—soft-bodied, flattened organisms—lack rigid internal or external skeletons, moving instead through undulating contractions of their bodies. Their thin, flexible structures allow for efficient gas exchange directly through their skin, eliminating the need for a complex respiratory system. However, these same traits also render them vulnerable to predation and competition, particularly against the dominant tristags, whose segmented bodies, specialized appendages, and complex life cycles give them a major ecological advantage. 

While tristags diversified into a vast array of mobile, specialized creatures—becoming hunters, filter feeders, grazers, and scavengers—platyglosses were unable to compete directly in most active niches. Their simple body plan prevented them from developing complex structures like articulated limbs, leaving them at a disadvantage in speed, maneuverability, and environmental awareness. Much like how Earth’s free-living flatworms are often overshadowed by more complex bilaterians, platyglosses found themselves outcompeted in the open waters and on the seafloor.

For added defense, sputoglosses have also adopted a form of Batesian mimicry by taking on a partially green coloration similar to the toxic teterstomes, a long-standing poisonous lineage in Atmos’s oceans. Over millions of years, many predators have learned to associate the green hue of teterstomes with danger, avoiding anything resembling them. While sputoglosses lack the same potent toxins as true teterstomes, its resemblance is often enough to dissuade would-be hunters.  This dual defense—both chemical and visual—has allowed sputoglosses to persist in environments where other platyglosses struggle. They can be found in shallow waters and reef-like structures, slithering along surfaces in search of microscopic food while remaining just unappetizing enough to avoid being eaten.

Microglosses primarily feed on bacterial mats, organic detritus, and microscopic cyanophytes, scraping nutrients from surfaces with their soft, absorbent mouths. Unlike their larger relatives, which rely on muscle contractions for movement, microglosses often drift passively with ocean currents, only actively crawling when necessary. Their flattened, ribbon-like bodies allow them to squeeze into the tiniest crevices of reefs, burrow between grains of sand, or even cling to the surfaces of larger marine organisms, living as harmless epibionts. Some species have adapted to a symbiotic lifestyle, hitching rides on slow-moving benthic creatures such as duocrustaplods and harenaceuplods in exchange for cleaning off biofilms and parasites. Others have become so small that they blend seamlessly into the microbial world, avoiding predators simply by existing below their detection threshold.