Adelaide

Scientists have uncovered a 500-million-year-old fossil in Canada that could help explain a puzzling gap in Earth’s evolutionary history known as the “Furongian gap”.

The discovery, detailed in a study published in the journal BMC Biology, suggests that the apparent decline in biodiversity during the late Cambrian period may not have been due to a mass biological crisis, but rather because scientists have not yet explored enough fossil-rich rock formations from that era.

The fossil belongs to an early arthropod — a group of animals with external skeletons that includes modern spiders, scorpions and insects. Researchers identified the newly described species as Magnicornaspis garwoodi, a rare member of the corcoraniids, an unusual group of ancient arthropods characterised by broad head shields, segmented bodies and defensive spines.

What makes the fossil especially significant are two large spines projecting from the animal’s head, a feature not previously seen in related species. Scientists believe these structures may point to defensive adaptations that evolved earlier than previously thought.

The specimen was originally collected in 1962 during geological surveys near Sainte-Anne-de-la-Pocatière in Québec, Canada. It was found in mudstones of the Rivière-du-Loup Formation, which formed in deep marine environments during the late Cambrian period.

Despite its importance, the fossil remained largely unnoticed for decades in the collections of the Smithsonian National Museum of Natural History in Washington DC.

Researchers say the discovery highlights the value of museum collections, where overlooked specimens can still reshape scientific understanding of ancient ecosystems.

Palaeontologists have long been puzzled by the Furongian gap — a period around 497 to 485 million years ago in which the fossil record appears sparse despite rich biodiversity before and after the interval.

Earlier theories suggested environmental instability, cooling climates, low oxygen levels or changes in ocean chemistry may have caused a collapse in marine life during that time.

However, recent discoveries from China, Sweden and now Canada are challenging that idea. Scientists now believe ecosystems during the late Cambrian may have remained far more diverse and complex than previously assumed.

The Québec fossil also expands the known geographic range of well-preserved Cambrian fossils, showing that the ancient Appalachian margin of eastern Laurentia — a prehistoric continent that included much of present-day North America and Greenland — was capable of preserving delicate organisms.

Researchers argue that the Furongian gap may partly be the result of an “anthropogenic bias” — meaning the fossil record appears incomplete because of where humans have searched and studied rocks.

According to the study, many important fossils and even entire ecosystems from the late Cambrian may still remain hidden in museum drawers or in underexplored rock formations around the world.

READ MORE: Bashir Badr: people's poet whose words echoed from college canteens to political corridors

The researchers said the finding serves as a reminder that Earth’s evolutionary history is still far from fully understood, and that major scientific breakthroughs may emerge not only from new excavations, but also from re-examining forgotten specimens collected decades ago.