The crow-like Confuciusornis, which lived about 120 million years ago, was one of the first birds to evolve a beak. Unfortunately, early beak evolution lacks sufficient study. Using an imaging technique called Laser-Stimulated Fluorescence (LSF), researchers at the University of Hong Kong (HKU) have addressed this problem by revealing just how different the beak and jaw of Confuciusornis are compared to birds today.

LSF is an imaging technique co-developed at HKU that involves shining a laser onto a target. It makes fossil bones – and the soft tissues preserved alongside them – glow in the dark. The technique has revealed fine skin details and other previously invisible soft tissue in a wide range of fossils, especially those of early birds and other feathered dinosaurs.

HKU Ph.D. student Case Vincent Miller and his supervisor, Research Assistant Professor Dr. Michael Pittman, led the study with Thomas G. Kaye of the Foundation for Scientific Advancement in Arizona and colleagues at the Shandong Tianyu Museum of Nature in China. Under LSF, which was co-developed by Pittman and Kaye, the team revealed the fingernail-like “soft beak” of Confuciusornis, a feature that covers the beak of every bird and is called the rhamphotheca. The example the team found in Confuciusornis was preserved detached from the bony part of the beak. “Fossilized rhamphothecae have been reported in fossil birds before,” said Pittman, “but no one has really asked what they tell us about the earliest beaked birds.”

The international research team reconstructed what the beak looked like in life and used this depiction to consolidate knowledge of the beak of Confuciusornis across all known specimens. In highlighting that the rhamphotheca was easily detachable and by performing the first test of jaw strength in a dinosaur-era bird, the team suggested that this early beaked bird was suited to eating soft foods. Finally, the team highlighted differences in how the beak is assembled to show that despite looking like living birds, the early beaks of Confuciusornis and its close relatives are fundamentally different structures to those seen in modern birds.

Regarding future plans, Miller said this research has raised a lot of interesting questions going forward. “We know so little about fossil rhamphothecae and plan on using LSF to study even more fossils to find more of these hidden gems.”