X-Ray Scan Reveals 445M-Year-Old 'Ghost' Fossils
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- Jonathan Aitchison at the University of Queensland and colleagues applied synchrotron-based micro-computed tomography to a rice-grain-sized pellet drilled from a 445-million-year-old black shale collected in late 2018 from China's Sichuan Basin.
- The X-ray scans revealed that radiolarian skeletons had dissolved away but left detailed hollow imprints later filled with bitumen and minerals, functioning like microscopic plaster casts of the Pompeii-victim mold type.
- The team identified eight radiolarian species, including one previously unknown to science, as detailed in a paper published in Royal Society Open Science (DOI: 10.1098/rsos.252091).
- The fossils predate the peak of the Late Ordovician mass extinction and come from a period when parts of the oceans were already losing oxygen, potentially illuminating how marine life responded to that environmental stress.
- The researchers note that radiolarians can be abundant in organic-rich black shales worldwide yet remain invisible to conventional acid-based extraction, which typically destroys delicate specimens.
- The study is based on a single small rock sample from one locality; the team now plans to scale the approach to longer cores and larger sample sets to search for more hidden fossils.
Why it matters: The method gives paleontologists a non-destructive way to read fossils preserved as mineral casts in black shales—rocks that are common globally but previously opaque to conventional extraction. That opens a new archive for studying how radiolarian zooplankton survived oceanic oxygen loss in the run-up to the Late Ordovician extinction, a data point useful for refining models of ecosystem resilience under past climate warming.
