By Damien Knight
The traditional study of morphology in paleontology is changing with the use of X-ray and tomography technologies. X-ray Computer Tomography (CT) Scanners and other X-ray techniques are aiding our understanding of fossils in greater detail. Traditional paleontology required digging fossils from their matrix which destroyed the samples to study them. New technology can penetrate dense rocks with resolution in the microns.
CT scanning means we now can examine fossils without damaging the sample. In the past fossil examination through tomography was a destructive process. This process is serial grinding. Serial grinding required manual grinding away of fossils, stopping at intervals then drawing 2D slices. Its start was with William Sollas, he would grind away at fossils only to stop at intervals to photograph or trace them. The process is time consuming and destroyed the fossil being examined.
Figure 1 Siemens Introskope Conventional Tomography 1934 (Left) Modern Micro-CT (Right) Photo: Siemens Medarchiv and Elsa Panciroli
X-ray Computer Tomography (CT scanning) has changed the way we examine fossils. Initially medical CT scanners were used but are low resolution and could not scan for fine details. The CT Scanner’s Paleontologists use today are different from the early medical scanners. They use the Micro-CT or µCT, which can penetrate dense rocks with higher doses of X-ray. µCT lets us remove fossils from host rocks digitally and examine without destroying the sample.
CT scanning can be used to detect bone and tissue on creatures trapped in amber. In 2016 The Guardian published an article detailing the use of CT scanning to detect bones and soft tissues in amber preserved tropical lizards from Myanmar (Panciroli, 2016). In mammals CT scanning can reveal fine details such as ear complexes encased in rock (Landman, 2018).
Figure 2 Cretaceous amber encased lizard fossil. Photograph: David Grimaldi
Figure 3 CT scan of lizards in amber. Photograph: David Grimaldi
CT scanning along with synchrotron radiation (SR) helps paleontologist gain a new understanding of the diversity of life. Using SR in paleontology reveals even further details when used to study fossils. SR has a larger photon energy range which allows finer details to be examined and allows for chemical analysis (Barbi, 2014). SR has the advantage of being powerful enough to examine dense material and is noninvasive, like CT. In the figure 4 taken from a “New Age of Morphology Takes Shape” article synchrotron microtomography radiation is used to expose radular teeth.
Figure 4 SR Microtomography scan of radular teeth in a buccal apparatus of a Baculites ammonite (Lanman, 2018).
The SR’s broad spectrum makes it sensitive to chemical elements. Different SR techniques provide a better understanding of fossil make up. The SR technique, X-ray fluorescence (XRF) is used to analyze chemical makeup and identify fossil bones from surrounding sediments or fossil plants. XRF also can be used to “differentiate species, based on fragmentary and non-traditional phenotypical character states,” (Barbi, 2014). For example Canada Light Source (CLS) used XRF to study the chemical composition of a Tyrannosaurus Rex, named Scotty, whose vertebrae analysis produced the Spectrum Comparison graph in fig 5. (Barbi, 2014)
Figure 5 XRF spectrum from T. rex bone (Barbi, 2014).
The X-Ray Absorption Near Edge Structure (XANES) works well with the XRF. The XRF reveals atoms present in fossils while XANES shows chemical state. In the study of the T. rex, Scotty, vertebrae they used this technique to distinguish Ca in sediment from bone. “The XANES spectra for x-ray absorption about the calcium edge of the T. rex bone… … depicts a different signature left by the calcium compared to that of the sediment,” (Barbi, 2014). This means the Ca in the bone was like apatite while the Ca in the sedimentwas like calcite.
Figure 6 Element Map of T. rex Vert (Barbi, 2014).
Figure 7 XANES Spectrafor T. rex vertebra (Barbi,2014).
The Fourier Transform Infrared Spectrometry (IR) was used in the T. rex Scotty vertebrae study with similar goals as XRF and XANES. IR interacts with the samples when certain molecules are present. When a molecule is present IR light “interacts with the sample, the wavelength corresponding to the vibrational state will be preferentially absorbed.” (Barbi, 2014) Once measured the absorption helps determine the molecule present. This helps with the search for organic molecules in fossils thought lost in diagenesis.
SR is changing how we view fossils and their preservation. In the study of Scotty’s vertebrae, it showed the fossils were distinguishable from their host sediment. It also showed that evidence of original organic material is preserved in the fossils. These types of discoveries in the past would have required destroying the samples, yet here we could use the same samples in multiple tests with no damage.
Throughout we have discussed the benefits of CT and SR scanning, such as the ability to study fossils in a nondestructive way. It also has benefits in education and industry. The ability to 3D print scanned fossils makes fossil study more accessible to the public. 3d printing and websites such as DigiMorph “allow rare fossils, including very large and very small and even those still embedded in rock, to be viewed in a dynamic way and interactive way…” (Cunningham, 2014). CT scanning is worth the costs.
Figure 8 Jaw of the early mammal Palaeoxonodon (top), digital reconstruction using CT scans (middle), the enlarged 3D printed version (bottom). Photograph: Roger Close (Panciroli,2016)
While the technology is revolutionary, there is a few cons. The biggest drawback is the expense. Funding for CT scanners at institutions was at one time a great anxiety. Institutions did not want to acquire them with the belief students would not want to learn the software. The National Science Foundation insisted scientist send samples to the national facility in Texas. “Thankfully, in the U.S. at least, NSF and Institutional Administrators changed their minds… … CT Scanners in universities and museums are now used 24 hours a day by scientists and students,” (Landman, 2018).
When they were not as common the cost to use the equipment along with the legal issues of data ownership were also a problem. If you used a museum scanner, they would have you sign data ownership documents stating data and 3D prints produced were their property. (Cunningham, 2014) Lastly, the scanners require large amounts of computer space for data storage. Storage space adds to the cost of using X-ray technology.
The analysis of fossils is more objective and reproducible, transforming our understanding of fossils (Cunningham,2014). It changes traditional study of fossil morphology via X-ray scanning technologies. Instead of traditional grinding or acid dissolving to see inside fossils we can examine fossils in a nondestructive manner. While costs are an issue CT and SR scanning has proven its use. With this new technology there is excitement and a better understanding of the shape and diversity of life (Landman, 2018).
Works Cited
Cunningham, J. A., Rahman, I. A., Lautenschlager, S., Rayfield, E. J., & Donoghue, P. C. (2014, May 10). A virtual world of paleontology. Retrieved November 24, 2018, from https://www.sciencedirect.com/science/article/pii/S0169534714000871
Daza, J. D., Stanley, E. L., Wagner, P., Bauer, A. M., & Grimaldi, D. A. (2016, March 01). Mid-Cretaceous amber fossils illuminate the past diversity of tropical lizards. Retrieved November 27, 2018, from http://advances.sciencemag.org/content/2/3/e1501080.full
Landman, N. H. (2018). A New Age of Morphology Takes Shape. Palaios (2018) 33 (7), 287-289.
Mauricio Barbi, T. T. (2014). Synchrotron Radiation as a Tool in Paleontology. Physics in Canada, 8-12.
Panciroli, E. (2016, March 30). Getting under a fossil’s skin: How CT scans have changed palaeontology. Retrieved from https://www.theguardian.com/science/2016/mar/30/getting-under-a-fossils-skin-how-ct-scans-have-changed-palaeontology-dinosaur-lizard
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