ananyo writes "Two species of African spiny mouse have been caught at something no other mammal is known to do — completely regenerating damaged tissue. The work could help improve wound healing in humans. The species — Acomys kempi and Acomys percivali — have skin that is brittle and easily torn, which helps them to escape predators by jettisoning patches of their skin when caught or bitten. Researchers report that whereas normal laboratory mice (Mus musculus) grow scar tissue when their skin is removed, African spiny mice can regrow complete suites of hair follicles, skin, sweat glands, fur and even cartilage (abstract). Tissue regeneration has not been seen in mammals before, though it is common in crustaceans, insects, reptiles and amphibians."