Symbiomats
Carpetesta and clingowhexia long intermingled within their shared range. Both made their home on any hard surfaces on the ocean floor. Carpetesta formed layers of mats, consisting of interconnected four-cell clumps, while clingowhexia existed as independent single cells. Significant gaps existed between carpetesta clumps, and clingowhexia would often settle within them. Each could sometimes eat the other.
Things changed with the rise of predation in the form of scrapercells. Suddenly, it became beneficial for carpetestans to have clingowhexia among them, as their flagella could ensnare the scrapercells, indirectly protecting the carpesta. The clingowhexia, too, survived best when there were several of them near each other, the better to take on a scrapercell. They benefited from living among carpesta too, as they could feed from their secretions.
Thus, the two species developed to form a single comingled mat, the symbiomat. Laminanimbus amicus forms the base structure, each four-cell clump connected to neighboring clumps by tentacles, with these networks forming stacked layers, one atop the next. The larger cells of Krakowhexia amica fill in the gaps, where they cling to Laminanimbus tentacles as well as the base surface.
In upper layers, the Laminanimbus filter-feeds, and the lower layers specialize in decomposition, all secreting nutrients to feed other parts of the mat. Upper Krakowhexia extend their flagella to grab passing cells for defense and food. In lower layers, they cling to the surrounding cells on all sides. At any point, Krakowhexia keep up photosynthesis to sustain themselves. But if they get sufficiently buried by higher levels of the mat, the low-level decomposition levels consume them. This final gift is their contribution to the mat's nourishment.
Symbiomats grow all over the ocean floor. (They often start to grow on wormreefs, but will quickly find themselves covered by new polyps. Dead reefs are fair game, however.) They can also extend into the tidal zone. This is a change for clingowhexia, as their soft cells were vulnerable to drying out. However, the uppermost layers of the Laminanimbus component can lock together to form, in effect, a thin skin over the mat, holding in the moisture until the tide returns. This does mean that the Krakowhexia components recede inside, so their flagella are no longer available, but as their predators are aquatic, this is not a problem.
Reproduction occurs entirely on a cellular level, by binary fission. (In Laminanimbus, the four cells in a clump split in tandem.) These new cells may join the existing mat or flow away somewhere else, to join another mat or start a new one. Within a mat, Laminanimbus are constantly able to exchange genetic material and organelles with their neighbors via their tentacles. The Krakowhexia part may exchange genetic material with any of their fellows that they physically touch.