Evolutionary loss of foot muscle during development with characteristics of atrophy and no evidence of cell death.

Many species that run or leap across sparsely vegetated habitats, including horses and deer, evolved the severe reduction or complete loss of foot muscles as skeletal elements elongated and digits were lost, and yet the developmental mechanisms remain unknown. Here, we report the natural loss of foot muscles in the bipedal jerboa, . Although adults have no muscles in their feet, newborn animals have muscles that rapidly disappear soon after birth.