Paleontologists have been offered unprecedented insight into the breeding practices of flying reptiles with the discovery of five largely intact pterosaur eggs. This more than doubles the number of eggs known from the many pterosaur species.
Maurilio Oliveira. A largely intact pterosaur egg from more than 100 million years ago.
Popularly known as pterodactyls after the first species in the order to be described, pterosaurs were the first vertebrates to evolve powered flight and dominated the skies from 228-66 million years ago. Their thin bones and powerful muscles allowed them to grow to a size birds and bats could never match. The largest pterosaurs had a 10m wingspan and may have weighed an intimidating 250kg.
While they were wiped out by the same forces that eliminated the dinosaurs and many other species at the end of the Cretaceous, smaller species had disappeared well before.
Based on the bones accompanying the eggs they come from a previously undescribed species from 100-120 million years ago in what is now Xinjang. The species has been named Hamipterus tianshanensis in Current Biology and is considered a new genus.
Male H tianshanensis skull
“We found a lot of pterosaur bones which belong to different individuals in the sites, with five eggs," said Xiaolin Wang, of the Chinese Academy of Sciences in Beijing.
While the thin bones were great for flight they didn't fossilize well, so relatively little is known about pterosaurs considering their diversity and longevity. More than 150 species have been identified, but this probably just scratches the surface of what once existed. Consequently the discovery of what may be thousands of bones from 40 individuals of both sexes, along with the eggs, is a major find. It is thought that many members of a breeding colony were wiped out together by a catastrophic storm. This supports previous theories that at least some pterosaurs were gregarious.
Chuang Zhao/PA. Reconstruction of a female H tianshanensis
Chuang Zhao/PA. The much larger crest is visible on the male
Only four previous eggs were known, and all had been flattened. While the H tianshanensis eggs are somewhat worse for wear, they are still intact enough to tell us the eggs had a hard but thin shell and a thick soft membrane layer like some modern snakes
Having both male and female specimens also helps settle a long standing question. There are indeed considerable differences between the crests of the sexes in size and shape, as seen in many species of crested birds.
Contrary to popular myth, birds did not evolve from pterosaurs, but had an entirely different ancestry, something that can be seen in the different ways their wings attach to the front finger bones.