They describe their study of the fossils and the dual tails - one long with feathers near the end, the other short and more useful for flying. (Agencies)
The fossil specimens were part of a large group of fossils found in a part of China known as Jehol - most of which were of different types of birds.
Jeholornis was previously thought to have just one long ornamental tail. This new study indicates that another was present also, situated much closer to the spine and very likely useful as an aid in flight.
Earlier efforts had led to finding 11 fossil specimens that had been identified as Jeholornis - four of them had feather and bone remains that showed the bird had a long tail with just a few feathers near the tip and also another tail that was much more like those of modern birds - a frond useful for steering while in flight.
The team noted that some of the other fossils did not appear to have both tails, suggesting that one of tails, likely the long ornamental one, existed in just one gender.
Its purpose, like the large plumes on some modern birds such as peacocks, likely was for attracting a mate.
Scientists believe that Jeholornis likely belonged to a class of birds that never made it to the modern era, dying off millions of years ago.
The study was published in the journal Proceedings of the National Academy of Sciences.
They describe their study of the fossils and the dual tails - one long with feathers near the end, the other short and more useful for flying.