Sunday 21 July 2019

Feathers may have evolved in lizards before birds

Pterosaurs were a group of flying lizards that had a covering of the earliest-known feathers
Pterosaurs were a group of flying lizards that had a covering of the earliest-known feathers

Jim Hurley - Nature Trail

The peculiar-looking creature in the illustration above is a pterosaur, a member of a group of flying lizards that became extinct some 66 million years ago. Pterosaurs did not have flight feathers and wings like modern birds; their wings were more like those of fruit bats with a membrane of skin stretching from their ankles to their fingers. They were the first back-boned animals to evolve true flapping flight.

Several pterosaur species, like the one above, were furry rather than being entirely scaly like modern lizards. And while they lived side by side with them from 230 to 66 million years ago, pterosaurs were not dinosaurs but were a distinct group of their own.

The illustration is by Yang Zhang from China's Nanjing University and is featured in the current issue of the journal Nature Ecology and Evolution. The drawing is based on a reconstruction of the flying lizard from two exceptionally well preserved fossils found in the Daohugou fossil beds in north-eastern China near Inner Mongolia.

The beautifully-preserved fossils were estimated to be 160-165 million year old. Examination of the detail preserved in them showed that the lizard had four different feather types over its ginger-brown head, neck, body, and wings: simple filaments or 'hairs', bunches or bundles of filaments, filaments with a tuft halfway down, and down feathers.

The significance of the fossil find is that it pushes the origin of feathers back 70 million years earlier than heretofore understood and suggests that feathers may have first evolved in lizards rather than in birds. However, the early rudimentary feathers were short, fuzzy and hair-like, so they could not have been used for flight; it appears more likely that they, like fur, were used for insulation against the cold.

It is believed that the fossil pterosaur had a wingspan of about 45cm, bigger than that of a Blackbird but smaller than a Jackdaw. It is likely that it lived in woodlands and probably fed on insects. Some pterosaurs, like the pterodactyls, had wingspans in excess of 10m and were the sharks of the ancient skies.

About 66 million years ago, an asteroid struck Earth with such devastating force that it led to the mass extinction of all pterosaurs, pterodactyls and dinosaurs.

The study of the lizard's feathers was led by researchers from Nanjing University in China, Dr Maria McNamara and Prof Patrick Orr from University College Cork, and Prof Mike Benton from the University of Bristol.

Fingal Independent