Ingrown Hedgestar
Externally the ingrown hedgestar hasn't changed much from its ancestor. They are larger and they supplement their diet with carrion. The lateral toes on their anal arm point forward, making them more effective as toes. The internal changes it has undergone are more significant however.
Ingrown hedgestars have developed a primitive endoskeleton made of pairs of curving keratin rods. Originally derived from the roots of their protective spines these skeletal rods embedded in the body wall were they provide attachment points for the muscles there. They are covered in a sheath of live cells which allow the rod to grow in diameter by adding new keratin fibers. Fibers are laid down in a cross-hatch pattern which makes them more resistant to chipping and splintering than they would be otherwise. The very first pair of rods are thicker and sturdier than the others and several of the muscles that pull the mouth back in are attached to these. Thanks to the support and leverage provided by this skeleton their anal arm is stronger than it was in their ancestor. Their skeleton also makes them decent swimmers, they pump their anal arm up and down in a similar fashion to that of Osteoastera.
Like their ancestor they lay large numbers of small eggs, generally over a hundred at a time. These eggs have live eggshells and can filter feed. Not only does this let them replenish the yolk but it even allows the eggs to grow larger after being laid. Larva hatch at nearly 2 mm in length, already bilateral and equipped with defensive spikes.