Methodologies for the visualization and reconstruction of three-dimensional fossils from the silurian herefordshire lagerstätte

The dominantly soft-bodied fauna of the Silurian (Wenlock) Herefordshire Lagerstätte of England is preserved as three-dimensional calcitic fossils within calcareous nodules. These fossils are difficult to interpret from study of sections produced by splitting, and are difficult also to isolate from their matrix. CT scanning of nodules is feasible, but is expensive and unlikely to be able to image the fossils at a sufficiently high resolution. We describe a technique based on serial grinding and digital photography which enables the capture of three-dimensional morphological information from the fossils. Computer video files are used to package the resulting datasets for inspection. Three-dimensional reconstructions can be created by a method involving the manual tracing of outlines on each image, but we consider this approach inappropriate in this instance. Datasets from grinding are treated instead as volumes, which are rendered either directly to produce virtual X-ray images, or by the computation of isosurfaces which are then visualized by ray-tracing. Rendering is performed from sequential angles to produce video files of rotating three-dimensional models. The method is illustrated with reconstructions of a trilobite and graptolite associated with the Herefordshire soft-bodied fauna, and of the wormlike mollusc Acaenoplax hayae. Reconstructions produced in this way can be retouched easily and manipulated to remove noise and preservational artifacts, to dissect out structures for detailed study, or to combine part and counterpart into a single reconstruction. The approach will provide the primary means of study of the Herefordshire fauna, and has the potential to provide a method of obtaining and/or communicating morphological information in a variety of palaeontological applications. Copyright: Palaeontological Association, 22 June 2001