For example, Struthiomimus is a genus within the family of Ornithomimosauria.
"Struthiomimus (meaning "ostrich mimic", from the Greek στρουθιον/strouthion meaning "ostrich" and μιμος/mimos meaning "mimic" or "imitator") is a genus of ornithomimid dinosaur from the late Cretaceous of Alberta, Canada. It was a long-legged, ostrich-like
In fact, it was not a dinosaur, but was a flightless bird that had developed from the basal pterosaur line. Such a bird is called a "secondarily flightless bird". (It is called "secondarily flightless" because they developed from creatures that were able to fly).
More to come.