X-ray microtomography as a tool to present and discuss new taxa: The example of Risananeiza sp. from the late Chattian of Porto Badisco

In many earth science studies, especially in palaeontology, examination and/or measurement of internal features of samples are routinely requested. X-ray computed tomography (CT) is for such tasks very well suited (CARLSON et alii, 2003). A variety of different X-ray CT instruments and techniques are now available: they can scan objects of a size range from less than one millimeter, to many decimeters and they can scan at different resolutions: from less than one micron (nanoCT) to one or a few microns (microCT), and up to the millimeters range (CT). The best-known advantage of X-ray CT is its ability to reconstruct quickly and nondestructively the interior of opaque solid objects in three dimensions when the density contrast is high enough to let the Xray differentiate the internal features (NEUES & EPPLE, 2008; METSCHER, 2009). The computed tomography is thus a powerful tool for biometric study as the obtained scans are scaled according to the reported voxel size and therefore suited for linear and volumetric measurements (SPEIJER et alii, 2008; BRIGUGLIO et alii, 2011; GÖRÖG et alii, 2012; HOHENEGGER & BRIGUGLIO, 2012). For many fossils, the X-ray CT may be the only practical means of gaining information on internal materials and geometries or other features hidden from external view (e.g., SPEIJER et alii, 2008). So far, the X-ray tomography is a well known technique and is extensively used in several earth science disciplines. As computed tomography allows quantification of the scanned material in all 3 spatial dimensions, the metric and biometric analyses represent the main field of application for xray methodology. The description of fossil forms and the quantification of some morphologic relevant parameter are the keys to investigate fossils for taxonomic purposes, and consequently for paleoenvironmental analyses and for biostratigraphic purposes. Measuring morphologic parameters of shells, bones or tests requires often the destruction of part of the body, or oriented cuts through the test. Since the prices for x-ray computed tomography working stations have became available for academia, the use of such technique is spreading in many geological and paleontological research institution.