Fossil mystery solved by flying reptiles' skeletons

With wingspans of less than eight inches (20cm), these hatchlings are among the smallest of all known pterosaurs

A post-mortem examination "150 million years in the making" has revealed how two prehistoric flying reptiles died.

Scientists at the University of Leicester identified two new fossils of pterosaurs with broken wings at the site of a prehistoric lagoon in southern Germany, which showed the pair of hatchlings died in a tropical storm.

The palaeontologists who made the discovery said the pterosaurs were "smashed from the sky" by the storm and were "rapidly buried at the bottom of a lagoon in fine muds whipped up by the same storm that killed them".

However, according to the university, the storm created the ideal conditions to preserve the pair and hundreds more fossils like them.

Fossilisation tends to favour the largest and most robust organisms, the university said, while small, fragile creatures rarely make it into the palaeontological record.

The 150-million-year-old fossils were discovered at the Solnhofen Limestones in Germany, an area that had yielded hundreds of pterosaur fossils.

Most were very small and "perfectly preserved", the university said.

Larger, adult pterosaurs were fragmented in the rare cases they were found.

The pterosaur skeletons are complete, articulated and virtually unchanged from when they died

Lead author of the study, Rab Smyth, from the university's centre for palaeobiology and biosphere evolution, said: "Pterosaurs had incredibly lightweight skeletons. Hollow, thin-walled bones are ideal for flight but terrible for fossilisation.

"The odds of preserving one are already slim and finding a fossil that tells you how the animal died is even rarer."

The discovery of the pterosaurs with broken wings, named Lucky and Lucky II by researchers, provided evidence of ancient tropical storms and how they shaped the fossil record.

Both skeletons show the same injury - a clean, slanted fracture to the humerus, which the university said was "unusual" and suggested a "powerful twisting force", like powerful gusts of wind.

Researchers said it seemed that larger and stronger individuals were able to weather storms.

"For centuries, scientists believed that the Solnhofen lagoon ecosystems were dominated by small pterosaurs," said Mr Smyth.

"But we now know this view is deeply biased. Many of these pterosaurs weren't native to the lagoon at all.

"Most are inexperienced juveniles that were likely living on nearby islands that were unfortunately caught up in powerful storms."