Three Ringed Rollogob
The three ringed rollogob is named for its two most prominent features, the fact that it travels by rolling and the fact that it has three rings of limbs. The middle ring of limbs is derived from a duplication of the ancestral hind limbs. Instead of developing at the base of the tail this ring develops at the midpoint between the first and third quartets of limbs. Because it is derived from the hind quartet this middle ring also has modified versions of the air sacs and cartilaginous “shelves” associated with the hind limbs. Cartilage-like tissue now forms a ring just below the skin which the limb's muscles are attached to. The other two cartilaginous regions have also expanded and now offer support to the first and last pair of limbs. They thus have three limb girdles, anterior, middle, and posterior. Longitudinal muscles connecting these three girdles allow them to be moved and even rotated relative to each other.
This ability to rotate their limbs allows them to more easily move by rolling. Most commonly they walk sideways in a cartwheeling motion by moving each limb individually to achieve a continuous rolling motion but they can also “ratchet” themselves. Ratcheting is accomplished by rotating the middle limbs while holding the anterior and posterior limbs angled forward and back respectively so they are slightly shorter then the middle ones. Once they have reached the limit of their rotation, they stretch the anterior and posterior limbs out so that they are slightly longer than the middle set and reset the middle limbs. They then lower themselves onto the middle set to begin the process over again. They have developed a claw like covering on the toes at the ends of their feet to protect them from abrasion damage. These claws are dull and comprised of strontium-compound reinforced keratin. The tail is usually held close to the body while in motion and is used mostly used to push off of obstacles and to prop them up onto their faces for feeding. The inside of the lips are studded with bumps of the same strontium-compound reinforced keratin that the claws are made of. By pressing their lips together and "kissing" food by slowly everting their lips they can scrape off small pieces of food that would otherwise be too big to eat.
Unlike other descendants of the gobbob the three ringed rollogob is diurnal. This is made possible by their tough rubbery skin which is resistant to punctures and desiccation but doesn't allow cutaneous respiration. Although they still use their mouths and vents for gas exchange they have also evolved an octet of simple lungs, one on either side of each of the middle legs. Derived from the air sacs copied along with the middle limbs these lungs are still quite primitive. Expansion and contraction is mostly incidental as muscles move around them for unrelated reasons.
Reproduction now takes place in freshwater but is similar to the gobbob's in many ways. Most reproduction involves the release of cloned larva but during times of physiological stress such as starvation they will spawn. Larva have three sets of fins with the first pair offset forty-five degrees from the middle and hind sets. During metamorphosis however they undergo torsion and the hind set of limbs along with the tail and vents twist forty-five degrees to the right.