"archaeopteryx" used to be considered the first bird. nowadays, it is not the only fossil of a bird-like dinosaur. a similar species called "anchiornis huxlei" lived from 160 to 155 million years ago. it had feathers on both front and rear legs, and could probably glide. it may or may not have had some ability to fly. this discovery means we cannot say "archaeopteryx" is the first known bird, but its contribution to science has been huge. we now know for sure that a whole group of small theropod dinosaurs had feathers, and that flight was a later, secondary, use of feathers. the first use of feathers was temperature regulation, and probably also signalling (see "epidexipteryx").