Feathers in their caps

• Published date: 27 May 2023

A well-received recent paper published in the journal Nature has shown that extinct flying reptiles, pterosaurs (‘‘pterodactyls’’), while mostly covered with short hair-like filaments, bore on some parts of their heads at least a few true branched feathers, which were brightly coloured and probably used for communication

This may indicate they were more closely related to dinosaurs than previously thought.

The work by a group of Belgian and Brazilian scientists at University College Cork, Ireland, analysed the head crest of a 115-million-year-old Brazilian pterosaur, Tupandactylus imperator. Its huge head crest bore a basal ring of fuzzy, branched true feathers which had melanophores of different sizes and shapes to produce different bright colours, under genetic control.

Pterosaurs, comprising the order Pterosauria (Owen, 1842), flew throughout the Mesozoic era and, like dinosaurs, became extinct about 65.5million years ago in the end-Cretaceous event. Prodigiously adapted for flight, pterosaurs were characterised by extreme elongation of the fourth finger of the ‘‘hand’’ to support a membranous wing that extended back to the ankle of the hind leg, and by a reduction of the hind limb. The fifth finger was vestigial and the first three fingers were free of the wing, enabling grasping and terrestrial locomotion on all four limbs.

Pterosaur bones were very thin — only 1mm-2mm thick, even in giant species. This immediately distinguishes pterosaur fossil bones from those of other vertebrates with hollow bones, such as birds and some dinosaurs, whose bones had thicker walls. Very thin walls lighten bones for flight, and walls only 1mm or 2mm wide enable the identification even of damaged, isolated fossil pterosaur bones. Other features unique to pterosaurs are the rod-like pteroid bone in the wrist and the long clawless first toe of the foot, not found in any other reptile. They were likely warm blooded. The overall shape of pterosaurs was unique and distinctive.

Pterosaurs were mostly brightly coloured and possessed physiologically sophisticated wings, the wingspan ranging from 20cm to 12.2m. On the ground, they walked on all fours.

Although there are no known fossils outside the Mesozoic era, it is likely that pterosaurs arose just before the Mesozoic, because even the...