The irondigger has replaced its ancestor. To dig deeper in the Alpine, their front legs have evolved into scooping claws. Their 4 other legs are still used for walking. The other side of their body is smaller and thicker now as it is used to balance out them. Their legs and scoopers are also double jointed for improved walking.
Their nostrils are much more sensitive to Iron to help them find food. They also look for other magnetic metals (like nickel and cobalt) to use to build up their shell and legs. Their metal shells are stronger (as well as being over their heads and legs leaving only the nostrils visible) now, protecting them in case of cave-ins when they are burrowing. They also have more organic tissue inside of them as they now eat more organic food, in the form of poo. However they still mainly eat Iron.