Laser-Stimulated Fluorescence of Aurorazhdarchid Pterosaur Shows Soft Tissues with Implications for Pterosaur Water Launch and Foraging Behaviour

Solnhofen Limestone is renowned for pterosaur discoveries including Pterodactylus, the first pterosaur species identified as a flying reptile. Here a Solnhofen aurorazhdarchid pterosaur specimen was imaged under Laser-Stimulated Fluorescence (LSF) showing its fossil soft tissues. The data recovered under LSF shows a distinct, well preserved actinofibrillar complex, an undistorted actinopatagium retaining the retrophalangeal connective tissue wedge and entire trailing edge, as well as webbed feet. These soft tissues are of particular interest for investigating water launch adaptations, because they include likely primary contact surfaces. Pterosaur launch performance has primarily focused on larger species. Here the soft tissue data supports the dynamic feasibility of small aurorazhdarchid water launch. Our model suggests that webbed feet might be an important water launch specialization, having a significant impact on launch performance. However, webbed feet appear to be plesiomorphic for most pterosaurs implying that they were probably exapted for water launch. Aquatic prey is important for many pterosaurs. The ability to water launch was likely important in all water-feeding pterosaurs. Wider future efforts to study water launch across pterosaurs should prioritise three key factors that limit its performance: available propulsive contact area, forelimb extension range and forelimb extension power about the shoulder.