Heritage Cases

Coprolites can be used to reconstruct ancient food webs and to sample smaller species (such as insects and microvertebrates) that are otherwise uncommon in the fossil record. These are critical data for ecosystem reconstruction. Such evidence is currently lacking in our understanding of the recovery period after the Permo-Triassic Extinction, which occurred some 252 million years ago and wiped out 95% of all species. Fossils from Driefontein Farm 11, in South Africa’s Free State province document a rare, Early Triassic freshwater ecosystem including sharks, fishes, mammal-like reptiles, archosaurs, and other vertebrates. Importantly, Driefontein 11 has produced more than 30 000 coprolites of diverse sizes, shapes, and perpetrators. These coprolites have the potential to provide a rich, unprecedented source of data about biotic recovery after the world’s worst extinction. Coprolites contain direct evidence of the feeding biology of extinct organisms. Coprolites are relatively common in the fossil record and have a long history of classical means of study, including destructive sampling to study their organic inclusions1-4. However, recent pioneering work3 using PPCSRmCT on coprolites generated 3D-reconstruction of inclusions inaccessible by classical investigation, including a whole new family of beetles. We propose to study 30 promising Early Triassic coprolites from Driefontein 11. A subset of these have been previously scanned using laboratory CT machines and shown to have myriad fossil inclusions, such as lungfish tooth plates, tetrapod maxillae, diverse fish scales, bivalve molluscs, and beetles. Our aim is to segment and develop 3D digital visualizations of these inclusions to identify them at more precise taxonomic levels, and to use material cross-sections and three-dimensional properties to study the fabric of the coprolites to determine their origins. Specimens are 30 individual coprolites, with min/max lengths of >1mm–70mm and min/max diameters of <1mm–40mm. They have cylindrical or spherical morphologies well-suited for tomographic scanning, and they can be batch-scanned in acrylic tubular housings already employed by the ESRF for other fossils. The samples will be scanned in two sets of experiments using propagation phase-contrast synchrotron microtomography (PPC-SRμCT) at beamline BM05 or ID19 of the European Synchrotron Radiation Facility (ESRF). Phase contrast is required to discriminate between the material inclusions and groundmass of the coprolites, which have only subtle differences in their density. The largest samples will be scanned at a resolution that will incorporate the complete sample in the field of view in half-acquisition mode and then increasing resolution to incorporate smaller samples in the field of view in half-acquisition mode. Scanning will proceed at three different voxel sizes, ~6 μm for complete scan of larger specimens, and ~1.4μm depending on the size of the smaller specimens. Region of interests (ROI) will be identified from the first series of scans within the coprolites (e.g. significant inclusions or insects) and a second experiment to scan ROI’s at higher resolutions (~1.4 – 0.35 μm) scheduled a month or two after the first experiment, to scan ROIs at higher resolutions. Due to the size and density of the fossils, we are requesting the beamline BM05 or ID19 of the ESRF which are the best suited beamlines for this type of experiment given the multiresolution phase contrast propagation scan techniques required. We are requesting 9 shifts for the first experiment, and 9 shifts for the second experiment. Results expected and their significance in the respective field of research : This will be the first study of Early Triassic coprolites and as such will provide novel information on the post extinction ecosystem dynamics globally. We will document new species of beetles, mollusks, and tetrapods, and assess broader evolutionary questions such as the trophic structures of ecosystems. The novelty of this work will result in high profile publications showcasing the capabilities of the synchrotron to provide further data of problematic fossil remains. The data generated from these scans will also form the basis of the lead applicants PhD thesis. Statement why this study cannot be done in South Africa: Due to the incredibly small scale of the coprolite inclusions, we require exceptionally high resolution to see diagnostic features. Micro-computed tomography has shown the presence of key inclusions but even at its maximum resolution does not allow us to see the necessary diagnostic features. The only equipment that would is the European Synchrotron and Radiation Facility in Grenoble, France. A staff member of the palaeo beamline, Dr. Kathleen N Dollman, has offered use of her discretionary beam time to have these specimens scanned (separate addendum). In terms of security, the coprolite specimens are small so will comfortably fit into the safe at this facility and other material from the Evolutionary Studies Institute has been scanned at this facility without incident.