The Early Tristagmacene

The Magtrogs

During the early Tristagmacene, magtrogs solidified their dominance as the primary sessile heterotrophs, diversifying into an array of specialized forms that shaped the benthic landscapes of Atmos’s oceans. These creatures, anchored to the seafloor, evolved varied feeding strategies to capitalize on the abundant marine snow and passing organisms. 

One clade, Torretrogis (Towering Eaters), grew to monolithic proportions, their massive, rock-like bodies looming over the ocean floor like underwater cliffs. Their open, cavernous mouths, resembling shadowy grottoes, created natural suction currents that funneled drifting organic matter and small creatures into their digestive chambers. Some species developed layered, ridged structures along their interiors, forming intricate labyrinths where prey could become trapped before being slowly digested. Others slowed their metabolic processes to incredibly low rates, becoming akin to rock formations on the ocean floor. Some torretrog species developed symbiotic relationships with filter-feeding organisms that inhabited the edges of their mouths, benefiting from the steady supply of food while providing their massive hosts with an additional means of capturing plankton and detritus. 

Another distinctive clade of magtrogs, Trichostrogis (Hairy Eaters), took a different approach. Instead of sheer size, they relied on camouflage and passive trapping. Their outer surface became covered in dense, flexible filaments, resembling the benthic cyanophyte meadows that coated much of the ocean floor. These hairs not only enabled camouflage-they functioned as an elaborate trapping mechanism. Small, unsuspecting creatures seeking shelter among the false grasses would become entangled within the sticky, fibrous strands, unable to escape. Once caught, the hairs would slowly contract, guiding the prey toward the central, hidden mouth of the trichostrogs. 

The Sporepores

While the fingopores spread across the ocean's surfaces, the sporepores leveraged their efficient spore dispersal mechanisms to expand into diverse ecological niches. Their reproductive strategy allowed them to colonize environments inaccessible to other poremorphs, leading to the emergence of multiple specialized lineages. 

Pinguesporis (Fat Spores) developed large, swollen spore sacs filled with dense reserves of nutrients. These spore sacs allowed pinguespores to store energy for extended periods, making them exceptionally resilient in low-nutrient environments like the deep ocean or isolated seabeds where organic material was scarce. When conditions became favorable, the sacs would burst open, releasing a thick cloud of spores that blanketed the surrounding substrate, ensuring rapid colonization. Some species even evolved protective outer coatings on their spore sacs, delaying their release until triggered by environmental shifts, such as an influx of detritus or a change in ocean currents.

Hydrusporis (Many-Headed Spores) developed a unique branching structure, with multiple small, bulbous spore nodes extending from a central body. These nodes periodically detached and drifted with the currents, allowing hydruspores to colonize vast stretches of the ocean floor. Unlike other sporepores, which primarily spread through passive dispersal, hydruspores exhibited a form of adaptive fragmentation-if a section was disturbed or broken off, it could survive independently and establish a new colony elsewhere. This ability made them particularly successful in turbulent, shifting environments, such as coastal shelves, hydrothermal vent regions, and deep-sea trenches where sediment frequently shifted. 

The Tristags

The descendants of the tristags would leverage their unique advantages, such as their internal skeletons, bilateral symmetry, and efficient nutrient intake and excretion, ultimately becoming the most successful of the heterotrophs. During the Tristagmacene, they would evolve into a great many forms, each of which would conquer Atmos in its own way.

Miruvermis

Miruvermis (Strange Worms) is a lineage of elongated, segmented organisms descended from the tristags. These worm-like heterotrophs possess five distinct bodily segments, each specializing in a different function, allowing them to exploit multiple ecological niches. Their anterior segment, or head segment, contains the mouth, eyes, primary sensory structures, and respiratory pores. Some species possess fleshy tendrils around their mouths, which help detect food in dark or murky water. Their four eyes, positioned in pairs, provide them with an expanded field of vision, useful for detecting movement and changes in light intensity. Unlike their tristag ancestors, whose vision was primarily limited to sensing brightness, some miruverms developed improved photoreceptors, granting them the ability to track slow-moving prey and discern basic shapes. One of their most notable adaptations is their unique respiratory system. Miruverms breathe by drawing water into their mouths, extracting oxygen internally, and expelling deoxygenated water through lateral pores located at the back of their necks. 

Their second, third, and fourth segments function for weighting and/or locomotion. Depending on the species, these segments function as either a flexible muscular structure, aiding in movement, or as a densely packed weight-bearing segment, stabilizing burrowing species. In free-swimming species, these segments serve as an anchor point for powerful undulating movements. In benthic variants, they act as a central pivot for burrowing or clinging to surfaces. Finally, their tail segment ends in a flattened fin, flexible barb, or rudder-like extension, depending on the species. 

While seemingly simple organisms, miruverms are among the most diverse tristag-descended clades of the early Tristagmacene, with species found in open water, deep-sea trenches, and burrowing through seabeds. Some retain their free-swimming lifestyle, while others have adapted to semi-sessile scavenging or parasitic feeding behaviors. 

Pleruplodis

Pleruplodis (Many Legs) represents the other major offshoot of the tristag lineage, evolving into elongated, multi-limbed organisms that thrived in benthic and crawling niches across the ocean floor. These tristags are distinguished by their thirteen pairs of legs, which propel them along sediment, rocky outcrops, and even the surfaces of larger marine organisms.

Their locomotion is driven by hydrostatic propulsion, with pressurized internal fluid assisting in limb movement. This hydraulic system allows their legs to function with remarkable flexibility, enabling both crawling and swimming adaptations. Some species even utilize the first two pairs of legs as specialized tentacular appendages, useful for grasping food, exploring their surroundings, or even fending off potential threats.

A key evolutionary shift in pleruplods is the modification of the internal skeleton of their tristag ancestors. Unlike their miruverm relatives, which retained an internalized structure, pleruplods evolved a hardened exoskeletal plate along their dorsal side. This protective shell acts both as a means of protection against predators and as a form of passive camouflage, helping benthic species blend into their environments by mimicking sand, rock, or aquatic vegetation. In some deep-sea species, the shell may take on a flexible, leathery texture, allowing for greater mobility while still offering protection.

Pleruplods have two forward-facing eyes at the front of their narrow, elongated bodies, providing binocular vision suited for detecting movement along the ocean floor. Unlike the more dispersed visual arrangements of some other tristag-descended lineages, the pleruplods’ eye placement supports a more directional lifestyle, supporting predatory and/or scavenging behaviors in various species.