In the case of Darwinopterus it is the head and neck that have changed, while the rest of the body remains in the ancestral state.

ECONOMIST: How new groups of creatures emerge

The fossils were found in northeast China earlier this year, embedded in rock dating back 160 million years, and have been called "Darwinopterus" after the renowned naturalist Charles Darwin.

CNN: Pterodactyl fossil fills gaps in evolutionary tale

"Darwinopterus came as quite a shock to us, " said David Unwin, from the University of Leicester's School of Museum Studies, which identified the creature, along with researchers from the Geological Institute of Beijing.

CNN: Pterodactyl fossil fills gaps in evolutionary tale

Lu Junchang of the Chinese Academy of Geological Sciences in Beijing and his colleagues, however, think that they may have done so in the case of a newly discovered flying reptile called Darwinopterus modularis.

ECONOMIST: How new groups of creatures emerge

As they report in the Proceedings of the Royal Society, the 160m-year-old Darwinopterus, which has been dug up in Liaoning Province, catches the flying reptiles in transition between the primitive, long-tailed forms exemplified by Rhamphorhynchus and the advanced, almost tailless creatures typified by Pteranodon.

ECONOMIST: How new groups of creatures emerge

"We had always expected a gap-filler with typically intermediate features such as a moderately elongate tail -- neither long nor short -- but the strange thing about Darwinopterus is that it has a head and neck just like that of advanced pterosaurs, while the rest of the skeleton, including a very long tail, is identical to that of primitive forms, " he said.

CNN: Pterodactyl fossil fills gaps in evolutionary tale