120-Million-Year-Old Fossil Reveals Mammal with Reptile-Like Teeth and Platypus Feet
A newly described Early Cretaceous mammal, Dongoconodon platycauda, challenges long-held views of mammalian evolution by exhibiting polyphyodonty (multiple tooth replacements) and semi-aquatic adaptations similar to modern platypuses and nutrias. Found in China, this 120-million-year-old specimen suggests that key mammalian traits like dental replacement and ear structure evolved independently rather than as a single package.