CT scan of a fossilized bryozoan with bioerosional trace fossils, specimen GIT 537-4714

The uploaded files contain X-ray Micro Computed Tomography (µCT) scans of a fossilized bryozoan colony, Esthoniopora subsphaerica (GIT 537-4714-1), that contain bioerosional trace fossils. The sample belongs to the GIT 537 collection at the Department of Geology, Tallinn University of Technology, Estonia. Digital images of the samples are also stored in the Geocollections database (https://geoloogia.info/en/specimen/301729). Micro-CT image acquisition and post-processing were done at the Central European Institute of Technology, Brno. Images were assessed for structures that indicate borings into the bryozoan colonies. The images are in are saved in a .vgl format, which can be viewed using softwares including VGSTUDIO MAX and Dragonfly. The images were made in an attempt to study the bioerosion revolution in Baltica. Bioerosional traces refer to borings in organic and inorganic substrates. Over time, these traces have infill, which may have a different texture from the substrate. The producers of these macroborings have evolved over time. However, the Middle–Late Ordovician was when the diversity of these bioerosional traces increased. In Baltoscandia, a shallow epeiric sea had emerged, and the prevalent environmental conditions favoured the precipitation of carbonates, which served as substrates within which organisms made borings. With over 15 macroboring ichnogenera identified in Baltic Palaeozoic carbonates, Baltica is believed to be the birthplace of bioerosion, and many undescribed macroborings still abound within the numerous hardgrounds and biogenic substrates. However, these bioerosional traces are not always clear because of diagenesis and taphonomy. Their real architecture is unknown, and they have more complicated structures that cannot be described in 2D. Non-destructive techniques are needed to describe them. Micro-Computed Tomography is a powerful non-destructive technique to describe structures hidden in hard substrates. It also has the added advantage of making 3-D images, animations, and serial sections through samples of interest. Hence, the resort to studying the samples using micro-CT. It is however acknowledged that using this method to study carbonate samples may be hindered due to poor contrast between the substrate and infill, as well as diagenesis and taphonomy. Examination of the bioerosional traces in the samples both in hand specimen and micro-CT show some complex structures that are yet to be assigned appropriate ichnotaxonomy. Acknowledgement: This project has received funding from the European Union’s Horizon Europe research and innovation programme under grant agreement No 101131765 (EXCITE2) for Transnational Access conducted at CEITEC Brno University of Technology.