Hidden details of dinosaur fossil revealed

The vast majority of dinosaur fossils preserve only the bones of the animal, but in very rare cases scientists get a much more detailed glimpse at what these extinct creatures might have looked like. China’s Liaoning province is one place that regularly yields up incredible fossils with traces of feathers, internal organs and even gut contents preserved.

Now researchers have used a new method to reveal details of the body, skin, feathers and scales of a dinosaur called Anchiornis, which are not visible to the naked eye. Known as laser-stimulated fluorescence (LSF), the technique uses a violet laser to stimulate molecules in remnants of organic tissues in the rock to fluoresce or glow in the dark. This effect can be captured on a special camera under dark conditions, revealing otherwise hidden details of fossils.

“We were able to directly observe parts of the body outline of a bird-like dinosaur,” says Hong Kong University palaeontologist Michael Pittman, one of the lead authors of a study reporting the find in the journal Nature Communications. “We also observed soft tissue details of the wings and feet that are usually extremely difficult to infer from studying fossil skeletons.”

Anchiornis is important for understanding both the origin of birds and of flight, Pittman says, as the crow-sized flying dinosaur is thought to be closely related to the ancestor of birds. The scans revealed foot pads and scales on the dinosaur very similar to those seen on chickens today, as well as small flaps of skin under the feathers on the leading edge of the wings. These are known as “propatagia” and are important for flight in birds. “Drumstick-shaped legs” and a thin feathery tail were also exposed.

The researchers chose Anchiornis for the study because it is one of the most common feathered dinosaurs found, with about 230 specimens held in Chinese museum collections. This meant the scientists had many fossils from which to select the best soft-tissue preservation.

“The method does work,” comments Mike Benton, a vertebrate palaeontologist at the University of Bristol who has been at the forefront of new techniques for studying dinosaur fossils. “I can see in this example that [LSF] can discriminate between rock and flesh. Often in the Chinese fossils there may be smooth areas around the bones which, in natural light, could be taken as either impressions of flesh or simply artefacts of preservation around the bones, such as the movement of water. The LSF, if appropriately treated, can be trained to discriminate between these two effects.”

LSF is a relatively new technique but has also been used to reveal camouflage patterning on the dinosaur Psittacosaurus, as well as the body shape of an early bird, Confuciusornis. A spectacular scan of a pterosaur – a flying reptilian contemporary of the dinosaurs – has revealed details of the eyeball completely invisible to the naked eye.

Fossils from Liaoning, such as those of Anchiornis, were created under unique conditions that provide an unparalleled snapshot of prehistoric life. “The remarkably preserved fossils were deposited in freshwater lakes with a regular input of sediments from nearby volcanoes,” explains the University of Manchester’s Phillip Manning, author of Grave Secrets of the Dinosaurs: Soft Tissues and Hard Science. “The rapid blanketing of the volcanic sediments was a major factor contributing to the exceptional level of preservation and might have contributed to the death of many of the animals.”