Phylum Ossacava
This is the dominant macrofaunal phylum of life on Hyperborea. These animals are descended from athropod-like ancestors possessing a jointed exoskeleton. A modified cuticle in the common ancestor developed into a skin-like layer which retained moisture on land and allowed for a reduction of the now endo-skeleton to only essential structural components. The ancestral bauplan possesses four-eyes, three pairs of limbs (a vestigial fourth pair exists only as tails), and one or two sets of mouthparts (the second set generally comprises a pharyngeal jaw). In some clades, such as birgs, the prothorax segments have become vertebra-like and function as a neck.
Indigo-iron complex in the blood fulfills the role of oxygenation and grants the flesh and blood a deep blue color when enriched. The bones are composed of a zinc ion and protein complex which makes them relatively lightweight and strong.