Fleshing Out Dinosaurs

Laser-stimulated fluorescence imaging was used to reconstruct the body outline of the bird-like feathered dinosaur Anchiornis. Colored areas represent different fossil specimens, corresponding to the insets.

Wang XL, Pittman M et al., Nat. Commun. 2017

Fossilized bones provide basic information about the shape of extinct species that have never been seen in the flesh. However, evidence of muscles, skin, and other soft tissue is vital to understand true body shape and movement patterns. How, for example, did some dinosaur species have the physical capacity to become airborne and evolve into the birds we know today? That kind of information has been lacking.

To fill this gap, an international team led by paleontologists Xiaoli Wang of Linyi University and Michael Pittman of Hong Kong University, both in China, applied a relatively new imaging method known as laser-stimulated fluorescence. This technique involving high-powered lasers enabled them to outline the otherwise hidden scraps of soft tissue left on fossilized dinosaur bones.

The researchers beamed violet lasers at more than 200 specimens of a small, bird-like dinosaur, called Anchiornis. In an otherwise dark room, the lasers brought out the mineral luminescence of various soft tissues, preserved in a few specimens, creating a glowing outline that researchers photographed with a filter-outfitted camera. The resulting high-definition images revealed the now-fluorescent outlines and textures of the feathered dinosaur’s tail, legs, and arms.

Alive roughly 160 million years ago, Anchiornis appears to have displayed a mix of features found in later bird-like dinosaurs, as well as modern birds. It sported a lithe tail that likely could move fairly independently of its somewhat bulbous thighs. The legs of Anchiornis tapered to chicken-like feet, complete with pebbly scales adorning the bottom of its footpads.

One particularly telling feature was the flap of skin along the front of the elbow known as the propatagium, which might have allowed for the same kind of straightwinged pose as pelicans and other gliding birds. By increasing the wing size, the propatagium could potentially contribute to the lift necessary for flight. However, the team believes the orderly pattern they found dotting these skin flaps indicates that, unlike modern birds, Anchiornis had uniform, symmetrically arranged feathers that might have offered different options for aerodynamics.

Armed with this imaging technique, researchers hope to highlight the fine details of other dinosaurs’ bodies and better understand how they moved. (Nature Communications)