Whirltooths are (relatively) small carnivores from the creed plains of Ageriul. Before it was discovered, it was believed that an unknown apodothere filled its niche. Now, though, it is known that this is the main predator of the abundant herds of tuarateh.
Like the apodotheres, the whirltooth's ancestors were aquatic lungfish-like animals, living in the vast prehistoric swamps of their continent. When the swamps disappeared, though, it was either adapt, move or die. Most of the xenopisces died or moved, going into the rivers. The ancestor of the whirltooth, however, adapted dramatically. It starting digging, using its scraf-jaws and four fins to help it dig and move along the surface. Over millions of years, it changed dramatically, becoming a creature unlike any archogigian ever on Ageriul before. Animals like these, though, didn't evolve fast enough to become the dominant diggers. The apodotheres got there first.
The whirltooth's teeth are its distinctive feature compared to other of Viperius' animals. They are lined up in a spiral along the inside of its mouth, letting it bite on to its prey, twist its head and get to the juicy flesh inside. It has no separation between the upper jaw and cranium. The bones fused soon after they started digging, as there were problems with dirt getting between. Their neck is only three bones long, and connects to a bone that, in most archogigians, joins the cranium, scrafs and skull directly together. In this animal, however, it connects to the chest, front limbs and neck. The front limbs are actually highly modified scrafs, with the digits once being claws on the mandibles for catching prey. They have many chemical receptors, letting them taste and smell with their legs. This bone also contains a single, small lung at the top.
The chest is mostly normal for an archogigan, except there are two lungs slipping between the rib-bones. This evolved from wrinkled skin at the top of the body that absorbed oxygen, which eventually formed two sacs, which then moved into the chest for safety. Their tail still retains their lateral-line spine, which lets them feel vibrations in the ground. They also have some tiny rays in their legs, which serve the same purpose.