The Late Stromacene

The Cyanophytes

Throughout the Stromacene, the cyanophytes have continued to diversify. By the Stromacene's end, the ocean floor was blanketed in a  thousand species of blue flora, each adapted to different environmental niches. From the grass-like Cyandirectis (Upright Blues), which formed dense, swaying meadows in the shallows, to the branching Cyanostirpis (Branching Blues), whose intricate, tree-like structures provided shelter for countless marine organisms, the cyanophytes have become the foundation of Atmos’s marine ecosystems. 

In deeper waters, Cyanotendris (Tendriled Blues) evolved long, filamentous strands, drifting in the currents to maximize light absorption, while some species, such as the Cyanolentis (Soft Blues), developed broad, undulating fronds that optimize surface area for photosynthesis, thriving in the dim, nutrient-rich depths. Others, like the Cyanocrustis (Crusted Blues), adapted to life in the harshest environments, forming tough, rock-like encrustations on submerged surfaces, even colonizing the exterior of some membranutriors. 

The increasing complexity of cyanophyte forests has led to profound ecological shifts, offering new habitats and food sources for evolving heterotrophic organisms. Sessile membranutriors like the poremorphs burrowed into their root-like structures, while serpostomes creeped between the towering cyanophyte stalks, consuming fallen detritus. Some luranutriors evolved grazing behaviors, stripping the cyanophytes of their nutrient-rich outer layers, while others have adapted to ambush prey within the dense, blue-green undergrowth.

The Membranutriors

Lithofloris

Lithoflora continued to diversify, blanketing vast stretches of the ocean floor in towering, vibrant structures that shaped the marine landscape. Unlike the cyanophytes, which primarily relied on rapid spread and surface coverage, lithoflora developed sturdier, mineralized exoskeletons, allowing them to grow taller and form massive reef-like formations. These structures provide shelter, food, and breeding grounds for countless marine organisms, making them one of the most ecologically significant autotrophs of the Stromacene seas.

 Among the most dominant groups are the Ardufloris (Towering Flowers), which formed rigid, coral-like forests that stretched toward the ocean’s light-filled surface. Their massive, calcified structures created labyrinthine ecosystems teeming with life, as sessile membranutriors anchored themselves to their trunks and luranutrior grazers picked at their nutrient-rich symbiotic layers. In contrast, the Tenufloris (Thin Flowers) took a different evolutionary path, developing flexible, ribbon-like appendages that swayed with the ocean currents. These organisms thrived in mid-depth waters, where their delicate, branching structures maximized exposure to light while serving as sanctuaries for smaller marine creatures. Some species evolved symbiotic relationships with filter-feeding heterotrophs, which took refuge among their swaying fronds while consuming plankton drawn to the lithoflora’s nutrient-rich surfaces.

Poremorphis

The poremorphs, by this point, largely diversified into two dominant lineages, each filling a unique niche in the benthic ecosystem. Fingoporis (Mold Pores) developed dense, creeping networks that spread across the seabed, forming mat-like colonies that slowly broke down organic matter. Their tendril-like extensions allowed them to engulf detritus directly, dissolving nutrients with specialized enzymes before absorbing them into their porous bodies. These organisms thrive din nutrient-rich regions, where decomposing plant and animal matter accumulates, sustaining vast, carpet-like growths that ripple with the movement of water. 

Sporeporis (Spore Pores), by contrast, evolved to leave most of their mass underground, consuming subsurface detritus through deep-reaching, root-like structures. Their most distinctive feature was the development of small, spore-bearing bulges that protruded above the sediment, releasing microscopig reproductive particles into the water. These spores drift with the currents, settling in new locations where they could establish underground colonies, much like Earth's fungi spreading through spores.

The Luranutriors

Praefixiasseculis ("Paraspikes")

Praefixiasseculis (Spiked Parasites), or "paraspikes," is a lineage descending from the luranutriors. This group has become the smallest of the heterotroph clade, and evolved a predatory lifestyle, latching onto larger hosts, siphoning nutrients directly from their bodies. Their elongated forms are lined with rows of curved, chitinous spikes along both their dorsal and ventral sides, allowing them to anchor themselves securely to their chosen hosts, resisting dislodgement by currents, movement, or even the host’s own defensive measures. 

To penetrate the protective layers of their hosts, paraspikes possess a needle-like feeding organ, a hollow, retractable proboscis that they could drive into flesh or softer tissue to extract bodily fluids. Some species specialized in piercing the exoskeletons of lithoflora symbiotes, draining sap-like nutrients from their autotrophic layers, while others target the soft underbellies of free-swimming animals, clinging to their undersides to avoid detection. 

Unlike many of their ossacorp relatives, paraspikes simplified their internal structures, relying heavily on their hosts for sustenance and metabolic regulation. Their digestive system is minimal, adapted only for processing nutrient-rich fluids, and their sensory organs are reduced, as they spend the majority of their lives attached to a single host. However, despite this simplified physiology, they have developed a highly specialized nervous system, allowing them to detect minute chemical shifts in their host’s body-adjusting their feeding behavior based on the host’s condition to avoid triggering immune response. 

Reproduction for paraspikes is equally stealthy and efficient. Paraspikes release microscopic larval forms into the water, which drift until they detect the chemical signature of an appropriate host. Upon contact, these larvae burrow into soft tissues or attach to external surfaces, growing rapidly into their spiked, anchor-like adult form. Some species engage in kleptoparasitism, attaching themselves to other parasites already embedded in a host, indirectly benefiting from their work.

Tristagmis

One descendant of the ossacorps, Tristagmis (Three Stages), was a wormlike organism that underwent a three-stage reproductive cycle, transitioning through distinct juvenalifer (infant), virifer (male), and matrifer (female) phases over its lifespan. Beginning as small, translucent larvae, juvenalifers drift through the ocean as filter-feeders, sustaining themselves on microscopic plankton. As they mature, they transform into virifers, the mobile male stage, characterized by muscular bodies and specialized reproductive structures for fertilization. After mating, virifers may undergo a final transformation into matrifers, growing significantly larger and becoming capable of carrying and laying eggs. Structurally, tristags were a notable innovation among early luranutriors, possessing not only an internal skeleton, but also a fully formed digestive system with an anterior mouth and posterior anus, and lateral spiracle-like openings along the neck for expelling deoxygenated water. 

The descendants of this clade of ossacorps would prove undoubtedly to be the most successful of the luranutriors. For that reason, the next period of life on Atmos would come to be known as the Tristagmacene.