Ancient eggs in one basket

– A dazzling discovery in northwestern China of hundreds of fossilised pterosaur eggs is providing fresh understanding of these flying reptiles that lived alongside the dinosaurs, including evidence that their babies were born flightless and needed parental care.

Scientists said on Thursday their research, published in the Journal of Science, unearthed 215 eggs of the fish-eating Hamipterus tianshanensis – a species whose adults had a crest atop an elongated skull, pointy teeth and a wingspan of more than 3.5m – including 16 eggs containing partial embryonic remains.

Fossils of hundreds of male and female adult Hamipterus individuals were found alongside juveniles and eggs at the Xinjiang Uygur Autonomous Region site, making this Cretaceous Period species that lived 120 million years ago perhaps the best understood of all pterosaurs.

“We want to call this region ‘Pterosaur Eden’,” said paleontologist Shunxing Jiang of the Chinese Academy of Sciences’ Institute of Vertebrate Paleontology and Paleoanthropology.

Pterosaurs were Earth’s first flying vertebrates. Birds and bats appeared later.

Until now, no pterosaur eggs had been found with embryos preserved in three dimensions. Up to 300 eggs may be present.

The embryonic bones indicated the hind legs of a baby Hamipterus developed more rapidly than crucial wing elements like the humerus bone, said paleontologist Alexander Kellner of Museu Nacional in Rio de Janeiro.

“Some birds can fly on the same day they break out from the egg, while some others will need a long period of parental care. Our conclusion is that a baby Hamipterus can walk but can’t fly,” Jiang said.

The researchers believe these pterosaurs lived in a bustling colony near a large freshwater lake. Kellner cited evidence that females gathered together to lay eggs in nesting colonies and returned over the years to the site.

They suspect the eggs and some juvenile and adult individuals were washed away from a nesting site in a storm and into the lake, where they were fossilised.

The oblong eggs, up to 7.2 cm long, were pliable with a thin, hard outer layer marked by cracking covering a thick membrane inner layer, resembling soft eggs of some modern snakes. –