Goldfuß was right: Soft part preservation in the late jurassic pterosaur scaphognathus crassirostris revealed by reflectance transformation imaging and ultraviolet light and the auspicious beginnings of paleo-art

Abstract

Reflectance Transformation Imaging (RTI) is a technique based on multiple digital photos with a fixed camera position and illumination from varying directions. These photos are processed to create an image file in which light source position and reflectance properties can be digitally modified. The method is frequently used in archaeology due to its abilities to visualize surface details. Here we apply RTI imaging to the holotype of the non-pterodactyloid pterosaur Scaphognathus crassirostris from the famous Solnhofen Lithographic Limestone of Late Jurassic age and compare the results with ultraviolet light (UV) imaging. The specimen is of particular historical interest since it was the first pterosaur for which a “fur-like” integument was described, by the German paleontologist and zoologist Georg August Goldfuß in 1831. His publication on this fossil includes detailed paleobiological inferences and culminates in the first published scientific life reconstruction of an extinct vertebrate in its environment. However, soft part preservation was not accepted by later scientists such as Herman von Meyer, and Goldfuß' work on soft part preservation, paleobiology and paleo-art was largely forgotten. With RTI and UV light, pycnofibres covering the neck and the body, as well as aktinofibrils and blood vessels on the wing membrane, were visualized on the Scaphognathus crassirostris specimen, largely confirming Goldfuß' observations. The application of RTI is technically easy and promising for paleontological studies, especially for flat fossils on slabs of sediment, where minor differences in relief might hold crucial information. To our knowledge, this is the first study to apply RTI to soft part preservation in vertebrate fossils.