Megaorthoceros Holdfasti

The megaorthoceros segnoneustes had proven themselves as a hardy species, but they still had their cons, as little as they may have been. One such con was that those inhabiting river habitats had to fight against the currents, swimming against it and keeping themselves buoyant. While not a superbly difficult thing to overcome, some of those segnoneustes in the Ichthy Polar River solved this problem with a cunning evolution, splitting from their ancestor and becoming known as the megaorthoceros holdfasti.

M. holdfasti have adapted their fins into pads that secrete a substance that allows them to remain attached to substrate such as rocks or fallen flora and other such objects along the riverbed. This allows them to no longer worry about having to keep their buoyancy and fight the currents all the time. However they are certainly not sessile, and can move around by swimming should they find themselves not successfully consuming smaller organisms or if something disturbs their feeding in some way. The sticky pads are known as holdfasts, and their budding larvae will also use their pads to aid in support in a similar manner to their many relatives' aiding in buoyancy. Another adaptation is a curve in their proboscis, which now curves upwards to allow it to stick out in the local currents more for easier access to smaller microbes to feast upon.

Males are still barely a spot in comparison to a female, and because of their naturally requiring to be more mobile than females, they now will swim while folding their fins backwards against their flagellum, allowing for a more streamlined body and therefore more efficient swimming. Even so, the fins are still utilized to change direction. Males are no longer chemovoric, however, and now consume microbes smaller than themselves like the females in a filter-feed style in order to increase efficiency along to coincide with their active lifestyle.

Budding female larvae will still eventually leave their parent female, but the loss of these extra holdfasts to hold it down won't stop it from being able to hold itself in place, it simply makes them less sturdy. Mating and other instinctual capabilities have not changed. Because regular segnoneustes inhabit the open areas of the river and the holdfasti inhabit the riverbed, they fill slightly different niches and co-exist peacefully.