Tiny Pterosaur Claims New Perch on Reptile Family Tree

From Scientific American:

The finding is preliminary, but if it holds, it could upend scientists’ view of pterosaurs’ evolution, and their eventual extinction 66 million years ago.

The fossils — an upper arm bone and vertebrae discovered on Hornby Island in British Columbia — came from a nearly full grown pterosaur that had a wingspan of just 1.5 metres and was about as tall as a housecat, scientists report on 31 August in Royal Society Open Science1. They suggest the existence of a species about 77 million years ago, during the late Cretaceous period, that was much smaller than the giant pterosaurs thought to dominate then.

“It’s quite different from other animals we’ve studied. There hasn’t really been evidence before of small pterosaurs at this time period,” says Elizabeth Martin-Silverstone, the study’s lead author and a palaeobiologist at the University of Southampton, UK.

She and her colleagues examined a thin slice of the arm bone — a humerus — and analysed it on a microscopic level, looking at how the bone had maintained and reworked itself to get an idea of the animal’s growth stage. They also found that the vertebrae were beginning to fuse together. Together, these demonstrated that it was nearly a full-grown adult when it died.

Pterosaurs’ bones were hollow, with thin walls, so relatively few have survived as fossils. And small pterosaurs are particularly tough to identify, which means that the fossils that have been found give a limited picture of the original diversity of the animals. But in recent years, scientists have discovered specimens that suggest pterosaurs grew larger as they evolved. The biggest yet known was the size of a small plane — and lived during the late Cretaceous …

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