Rhurm
The rhurm has split from their ancestors and moved to the open ocean of the southern Sagan 4 polar seas. They slowly began to develop the means of free-swimming locomotion. They swim awkwardly, in an indelicate serpentine manner, but the body plans and burrowing behaviors of their progenitors has lent itself well to free swimming. They have grown larger in the colder climates, and lacking any real predators on the outset of their expansion has allowed the rhurm to radiate widely along the southern seas.
They can be found scavenging along the sea beds, scooping up marine snow or decomposing organisms. During summer months, when the sunlight is plentiful, they can be found in large masses, feeding on the plentiful phytoplankton and breeding en masse. They have primitive limbs, little more than buds of flesh with an exoskeletal covering, but there is just enough mobility to allow them to move back-and-forth, allowing for both stirring up the seabed to release food and digging plots in the sand to bury their eggs.