A minuscule pellet of ancient rock, measuring only half the size of a rice grain, has unveiled 20 microscopic fossils from eight distinct species, including several previously unknown types. This significant discovery enhances our knowledge of the second-largest mass extinction known to science, while demonstrating how innovative analytical techniques can uncover neglected segments of the fossil record.

Jonathan Aitchison, a professor at the University of Queensland in Australia, was pivotal in extracting these pellets from rocks gathered in late 2018 from the Sichuan Basin in China, located approximately 300 kilometers south of Xi’an. These rocks date back 445 million years, situating them just prior to the late Ordovician mass extinction, ranked as the second most severe extinction event in the last half billion years.

The pellets contained eight species of radiolarians—single-celled plankton characterized by silica shells that continue to inhabit oceans today.

The discovered fossils encompass five genera, four families, and three orders, including a newly identified species named Haplotaniatum woufengensis.

The fossils are remarkably well-preserved, with both external and internal structures perfectly encased in asphalt, creating flawless impressions.

Patrick Smith, from the New South Wales Geological Survey in Sydney, Australia, remarked that the fossils were formed before the extinction event escalated.

“The quantity and diversity of fossils indicate that marine ecosystems, especially microscopic plankton communities, thrived just prior to the extinction,” Smith stated. “Ordovician oceans were significantly more biologically diverse than previously understood, especially on a microscopic scale. These fossils showcase a vibrant plankton community during a pivotal moment of environmental upheaval in Earth’s oceans.”

Traditionally, researchers have studied small fossils by using acid to dissolve surrounding rock, a process Aitchison notes is highly destructive.

In contrast, the study employed advanced X-ray technology (from the Australian Nuclear Science and Technology Organization’s synchrotron in Melbourne) to scan the rock pellets, yielding high-resolution 3D images of the contained fossils within seconds.

“Growing up, I was fascinated by ads for X-ray glasses that could see through objects,” Aitchison commented. “Now, I can ‘see’ these radiolarian plankton directly within the rocks without needing to remove them.”

“This represents the most significant technological advancement in my career,” he added.

Professor Aitchison concluded that the extensive life forms discovered in such a limited sample size imply that the marine biodiversity found in other Late Ordovician rocks might be “significantly underestimated.”

Smith emphasizes that a key takeaway from this study is that numerous fossils remain to be explored worldwide, “not due to a lack of specimens, but because our traditional methods are insufficient for detection and recovery.”