Scientists Identify 240-Million-Year-Old Mystery Ancient Marine Reptile

Radiography Imaging of a Middle Triassic Mixosaurid From Svalbard

Photograph of specimen PMO 219.250. Credit: Engelschiøn et al. PLOS ONE, CC-BY 4.0

New research reveals that sulfur minerals that make fossils in the Norwegian archipelago are especially well-suited to radiography.

X-ray analysis has led to the categorization of a previously-unidentified marine reptile fossil discovered in Edgeøya, Svalbard. The research was recently published in the journal PLOS ONE.  The study, conducted by Victoria S. Engelschiøn of the University of Oslo and her team, suggests that this method could reveal fresh insights about ancient life in the future.

The effectiveness of X-ray techniques in investigating well-conserved fossil remains is often dependent on the condition of preservation, which can vary greatly across different sites. Through this study, Engelschiøn and her team showed that fossils from the Middle Triassic Botneheia Formation in Svalbard, Norway, are particularly suitable for radiographic imaging.

Muen Plateau

An overlook of the Muen plateau as seen from the Muen mountain on Edgeøya, Svalbard. Marine reptiles are spread out across the plateau. Author VSE in red jacket for scale. Credit: Sofie Bernhardsen, CC-BY 4.0

The focus of this study is a fossil marine reptile whose remains are compressed and encased in shale. It lived around 240 million years ago, when Svalbard was covered by an ocean. After it died, it sank to the seafloor and was buried in the mud, then became extremely flattened over time. Originally excavated in 2008, the identity of this fossil has since been debated. X-ray imaging of the specimen revealed new details, including features of the skull and teeth that allowed researchers to conclude that this reptile most likely belongs to the ichthyosaur species Phalarodon atavus.

The authors also examined the mineralogy of fossils from this formation, identifying multiple forms of sulfate minerals, notably including sulfate baryte, which gives the fossils very high X-ray contrast, allowing for the high quality of radiographic imaging. The formation of these minerals is little understood but could be linked to conditions created by ancient volcanic activity. Thus, this study not only demonstrates the utility of X-ray techniques for studying these fossils, but also identifies conditions that can form fossils well-suited for these techniques, in Svalbard and potentially elsewhere.

The authors add: “The rocks from Svalbard are full of flattened marine reptiles. Our discovery of the exceptional X-Ray contrast means that we can learn much more about these ancient predators than we previously thought.”

Reference: “Exceptional X-Ray contrast: Radiography imaging of a Middle Triassic mixosaurid from Svalbard” by Victoria S. Engelschiøn, Aubrey J. Roberts, Ruben With and Øyvind Hammer, 31 May 2023, PLOS ONE.
DOI: 10.1371/journal.pone.0285939

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