The skull of Darwinopterus. © Lu Junchang
Researchers have identified a new type of flying reptile providing the first clear evidence of an unusual and controversial type of evolution.
More than 20 fossil skeletons of the new Pterosaur, including a number of complete sections, were discovered earlier this year in North-East China in Jurassic rocks, believed to date from more than 160 million years ago.
The species, discovered by researchers from the University of Leicester and the Geological Institute, Beijing, has been named Darwinopterus, meaning Darwin's wing, in honour of the 200th anniversary of Charles Darwin's birthday.
Although 10 million years older than the first bird, the long jaws, rows of razor sharp-pointed teeth and rather flexible neck suggest it may have been a hawk-like predator, catching and killing other flying creatures.
Scientists have long recognised two different groups of Pterosaurs: primitive long-tailed forms and their descendants, advanced short-tailed pterosaurs. The groups, identified in Darwin's time, had been separated by a large evolutionary gap, until now.
"The strangest 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," explained research team member David Unwin.
The fossilised skeleton of Darwinopterus. © Lu Jungchang
The geological age of Darwinopterus and peculiar combination of advanced and primitive features reveals a great deal about the evolution of advanced pterosaurs from their primitive ancestors.
"First it was quick, with lots of big changes concentrated into a short period of time," said Unwin.
"Second, whole groups of features (termed modules by the researchers) that form important structures such as the skull, the neck, or the tail seem to have evolved together."
"Frustratingly, these events are only rarely recorded by fossils. Darwin was acutely aware of this, as he noted in the Origin of species, and hoped one day fossils would help to fill these gaps. Darwinopterus is a small but important step in that direction."
However, as Darwinopterus shows, not all of the modules (features) changed at the same time.
The head and neck evolved first, followed later by the body, tail, wings and legs, suggesting natural selection was acting on and changing entire modules and not, as would normally be expected, just on single features. This supports the controversial idea of a relatively rapid, "modular" form of evolution.
Researchers say more work is needed to substantiate the idea of modular evolution. If proven true, it could also help to explain many other cases in which rapid large-scale evolution must have taken place.