Paleontologists say the unearthing in Brazil of almost 50 fossil skeletons of an ancient flying reptile sporting a bizarre butterfly-like crest on its head is an "absolutely unprecedented" find.

The fossils of a previously unknown species of pterosaur, flying reptiles that were distant cousins of ground-bound dinosaurs, were discovered in a huge bone bed in southern Brazil, in what was an ancient dry region 87 to 75 million years ago dubbed the Caiua Desert.

The new species, named Caiuajara dobruskii, existed in a lake oasis in that desert and carried a extraordinary bony crest atop its head resembling a butterfly's wings.

It possessed a wingspan that would have allowed it to begin flying at a very early age, the researchers say.

Hundreds of bone fragments found in an area of just 215 square feet, strongly suggested the creatures were social creatures living together in large groups or colonies, says study co-author Alexander Kellner of Brazil's Museu Nacional/Universidade Federal do Rio de Janeiro.

Other scientists suggested the pterosaurs may have lived in flocks, similar to the way flamingoes do today, and may have been attracted to the oasis of an inland lake in the otherwise arid landscape.

Although pterosaurs have been unearthed on every continent, usually the fragile wing bones of the creatures don't preserve well, which made the huge number of well-preserved skeletons at the Brazil site all the more remarkable, he said.

"To be honest with you, when they first told me they had pterosaur bones, I was going, 'Yeah, sure,'" Kellner said.

"To find part of what could be part of a [pterosaur] population is really splendid," he said.

The bones protruding from the earth were first noticed in 1971, although paleontological excavations didn't begin in earnest until several years ago.

How the group of pterosaurs all died together is unknown, the scientists say, but it is thought a desert storm could have caused their demise.

The large number of skeletons allowed the paleontologists to follow the development of this particular pterosaur species from youth to full adulthood.

Writing in the journal PLOS ONE, the researchers say their study suggests young pterosaurs were able to fend for themselves and were not dependent on care provided by their parents.

They infer that from the fact the juvenile flying reptiles were miniature versions of the adults, already possessing the signature head crests and almost certainly capable of flight very soon after birth, they said.