It has recently been discovered that the pterosaur, a flying reptile that frequently appears in Hollywood sci-fi thrillers depicting the era of dinosaurs, laid eggs rather than giving birth in mammalian fashion.

Two Chinese paleontologists have published their fossil find of a pterosaur embryo, the first of its kind in the world, in the latest issue of the science journal, Nature, ending the long-time search for clues to corroborate the belief that the pterosaur was an egg-layer.

Pterosaurs were contemporaries of the dinosaurs and abounded in the Early Cretaceous period around 121 million years ago, the time from which the fossil dates.

"Dinosaur embryos have been discovered all over the world, but so far no pterosaur embryos have been reported," said Zhou Zhonghe, a researcher from the Institute of Vertebrate Palaeontology and Palaeoanthropology of the Chinese Academy of Sciences, in the magazine Nature.

According to Zhou, the fossil was discovered in the lake shales at Jin'gangshan in western Liaoning Province, in Northeast China.

Famous among paleontologists, the area is referred to as the Jehol Biota. ("Biota" is a term used to refer to the diverse flora and fauna of a given region.) Zhou and his colleagues have found many fossils there, including that of the feathered dinosaur, which has rewritten palaeontological history.

Dating techniques show the fossil-bearing deposit is 121 million years old, indicating that the fossil is from the end of the Early Cretaceous period. Many more fossils from the same horizon, or geological stratum, have been found in the same region, according to Zhou.

Zhou and the paper's co-author, Wang Xiaolin, noted that a careful examination proved the fossil embryo is "unambiguously a pterosaur." Its well-developed shoulder and chest bones, and the elongated fourth finger, mark it out as a pterosaur, according to Wang.

The pterosaur's wing membrane fibers are well preserved, together with some wing phalanges. Large patches of skin imprints are also preserved, mainly in the rear part of the body.

Zhou said that the fact the embryo is very well formed suggests that this pterosaur embryo was probably enjoying its last few days in the egg before hatching out to walk on the Early Cretaceous Earth.

The embryo has a wingspan of 27 centimetres, indicating that it would have matured into a medium-to-large pterosaur, according to the scientist.

Preservation of such delicate tissues with the skeleton and eggshell probably indicates that the embryo was killed in some sort of natural disaster.

Zhou and Wang believe that an event such as a volcanic eruption could have caused the quick death and preservation of the egg and embryo intact.

Wang was quoted by the magazine as saying that the tiny creature also gives us a new insight into the world of pterosaurs. Only 53 millimeters in length and 41 millimeters in diameter, the egg is slightly smaller than a typical hen's egg.

But its 27-centimetre wingspan would have more than quadrupled by adulthood.

Zhou and Wang also noted that the baby pterosaur would have been an early developer, like the chicks of many modern birds.

"The well developed wings suggest that it would have been able to fly and feed independent of its parents soon after it hatched," Wang said.

(China Daily June 14, 2004)