The last trilobites became extinct more than 250 million years ago, but the first fossils of trilobites appeared from the early Cambrian period, about 540 million years ago. Studies have mainly been of fossils exposed on the surface of rock slabs, and attempts to study structures preserved inside the slabs required removing the matrix, the natural rock that surrounds the fossil, which often can damage the specimen. Because of its non-destructive qualities, micro-CT is ideal for studying fossilized trilobites that are situated within a fossil slab.
X-Ray Microscopic Imaging of a Fossilized Trilobite
A fossilized trilobite sample was imaged using our high-power SkyScan 1273 micro-CT with an isotropic voxel size of 20 µm. With a 130kV X-ray source capable of operating at up to 39W of power, the SkyScan 1273 is a great match for small fossil samples where density can be a concern on lower-powered instruments.
As shown in Figure 2, DataViewer provides us with a linked set of 2D images through the coordinate planes of the sample and allows us to fine tune the orientation of the sample within 3D space for downstream datasets. The trilobite portion of the sample contains dense mineral grains. which show up as bright white spots. Additionally, the trilobite portion of the sample also shows up with higher attenuation than the remaining rock sample, as can be seen in the different gray values for the trilobite and the surrounding rock. This differential attenuation will allow us to segment the trilobite out of the larger sample volume with relative ease.
Using CTVox, we digitally sliced into the trilobite to explore the local features and structures present within the sample.
Likewise, if we want to look more broadly through the sample at regions of different intensity, CTVox allows us to view the dataset as a maximum intensity projection image, as shown in Figure 4. This view renders the dataset mostly transparent with coloration directly resulting from apparent density and highlights the densest regions of the sample.
Conclusion
Among the SkyScan product line, the SkyScan 1273 is a workhorse instrument with the most flexibility for different sample types. As the highest-powered desktop model available within the SkyScan portfolio, the SkyScan 1273 is a great match for imaging small fossils and notable historical artifacts.
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Scan Specifications
| Sample | Trilobite Fossil |
| Voltage (kV) | 130 |
| Current (µA) | 115 |
| Filter | 1 mm Copper |
| Voxel Size (nm) | 20 |
| Rotation Step | 0.2 |
| Exposure Time (ms) | 1831 |
| Rotation Extent (deg.) | 360 |
| Scan Time (HH:MM:SS) | 08:44:27 |
These scans were completed on our SkyScan 1273 micro-CT system at the Micro Photonics Imaging Laboratory in Allentown, PA. Reconstructions were completed using NRecon 2.0 while visualization and volumetric inspection of the 2D and 3D results were completed using DataViewer and CTVox. The rock and fossilized trilobite were converted to STL volumetric models using Synopsys’ Simpleware ScanIP software with the CAD add-on module (Synopsys, Inc., Mountain View, USA) before 3D rendering using Maverick Render Indie (Random Control, Madrid, Spain).
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