Scientists say "Ida," a 47-million-year-old fossil, may be a critical missing-link species that bridges the evolutionary divide between higher primates(霊長類)such as monkeys, apes, and humans and their more distant relatives such as lemurs(キツネザル). Analysis revealed that the talus bone(距骨)in her ankle is the same shape as the one in humans and that she possesses opposable(向い合せにできる)big toes and clawless(かぎ爪のない)digits(指)with nails - features commonly associated with primates. The creature, whose scientific name is Darwinius masillae, is about the size of a cat, has four legs and a long tail, and fed on fruit and leaves.