In 1962, a geologist surveying rock formations near Québec pulled a thumb-sized creature from a slab of black shale and shipped it to Washington. It was cataloged, stored, and pretty much forgotten. More than six decades later, a team of paleontologists returned to the specimen and took a closer look.
What the team saw was a 500-million-year-old arthropod, a distant relative of spiders and scorpions, from one of the least-understood windows in evolutionary history. Published in BMC Biology, the discovery of Magnicornaspis garwoodi by researchers at Flinders University in Australia and Germany's Karlsruhe Institute of Technology suggests the late Cambrian may not have been as empty as the fossil record makes it seem. Instead, researchers may have been missing part of the story by overlooking the kinds of rocks most likely to preserve delicate, soft-bodied animals.
“Paleontologists have wondered whether this time of markedly less diversity of life could be linked to ocean chemistry, cooling climates, or environmental instability,” co-author Russell Bicknell said in a press release. “But perhaps we haven’t been looking at the right sedimentary rocks or fossil-bearing deposits.”
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A 500-Million-Year-Old Arthropod Fossil Turns Up in a Sparse Stretch of Time
From roughly 497 million to 485 million years ago, fossils became harder to find. Sandwiched between two major turning points in animal evolution, the Cambrian radiation and the Great Ordovician Biodiversification Event, the Furongian has looked like a missing chapter.
That is what makes Magnicornaspis so useful. Instead of just adding one more fossil to the record, it offers a clearer view of the kinds of animals that may have been living during this poorly understood interval.
The animal belongs to a family called the corcoraniids, an early group of arthropods with head shields, segmented bodies, and, in this specimen’s case, large forward-pointing spines near the front of the head shield. Those spines are part of what makes the fossil stand out. Other Cambrian corcoraniids either lacked prominent spines or carried them along the back and tail. Forward-pointing head spines like these had previously been known only from younger Ordovician relatives.
That means this defensive design appeared earlier than researchers had recognized. It also gives paleontologists another sign that late Cambrian ecosystems may have been more varied than previously believed.
Québec’s Rivière-du-Loup Formation May Hold More Soft-Bodied Fossils
In this case, the rock around the animal matters almost as much as the animal itself. Magnicornaspis came from Québec’s Rivière-du-Loup Formation, which had not been known for preserving fossils such as these.
When the team examined the specimen with scanning electron microscopy, they found calcium phosphate and carbon-rich traces in the fossil. That combination points to a level of preservation that researchers did not expect from this deposit.
That may put the Rivière-du-Loup Formation among what researchers call Konservat-Lagerstätten, fossil deposits where delicate animals can leave more than just hard shells behind.
A Museum Fossil Shows the Value of Looking Again
The new species was named for Manchester University paleontologist Russell Garwood, whose work has helped trace chelicerate evolution.
The discovery also shows why older collections are worth revisiting. The fossil had been collected during geological mapping in 1962 and preserved in the Smithsonian’s collections until researchers took another look at it with modern tools.
“This highlights one of the most important aspects of paleontology: major discoveries do not always emerge directly from fieldwork,” said Julien Kimmig from Germany’s Karlsruhe Institute of Technology (KIT) in the press release. “Museum collections contain enormous quantities of under-studied material collected during geological surveys and expeditions over the past century. Revisiting these collections with modern techniques can fundamentally reshape understanding of ancient ecosystems.”
For researchers, Magnicornaspis shows that the Furongian gap is not just about what was preserved. It is also about what scientists know to look for.
Read More: How Index Fossils Help Reconstruct Earth's Ancient and Mysterious Past
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- This article references information from a study published in BMC Biology: New exceptionally preserved arthropod from the Furongian of Canada
