Friday, 29 May 2026, 7:35 pm
Article: The Conversation
Russell
Dean Christopher Bicknell, Flinders
University and Julien
Kimmig
Roughly 500 million years ago, a
strange event in the evolution of life on Earth seems to
have taken place.
The known fossil record from
this time, which falls within the Cambrian period, contains
a missing chapter. Palaeontologists refer to it as the “Furongian
gap”. And it’s striking because there is an
explosion of biodiversity within the fossil record both
immediately before and after it.
This decline
has been considered evidence for a real biological crisis
– one driven by environmental instability, changing ocean
chemistry, cooling climates, a lack of oxygen in ancient
seas, or a combination of these factors.
Our new
study,
published in the journal BMC Biology, provides new evidence
for an alternative idea. The Furongian may not represent a
true collapse in biodiversity, but rather a gap in where
scientists have looked and what kinds of rocks have been
studied.
It’s a reminder of how incomplete our
understanding of Earth’s history remains.
A rare group of fossils
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We
describe a new 500-million-year-old arthropod from Québec,
Canada. Arthropods are animals with exoskeletons – that
is, skeletons on the exterior of their bodies.
The
fossil belongs to a rare group of early arthropods related
to the lineage leading to spiders and scorpions.
Importantly, it comes from a geological setting that
scientists have not previously recognised as being notable
for preserving fossils at this time in Earth’s
history.
The fossil itself is named
Magnicornaspis garwoodi. The animal belongs to the
corcoraniids – an enigmatic group of early arthropods that
have broad head shields, segmented bodies, and defensive
spines.
Corcoraniids remain exceptionally rare
globally. Only a handful of species are known from the Cambrian
and Ordovician
periods.
Our specimen is unique for its two large
forward-projecting spines extending from the head. These
exaggerated spines distinguish the species from previously
known relatives. They
suggest defensive adaptations within the group evolved
earlier than previously recognised.
Sitting in a
museum drawer for decades
The specimen was
originally collected in 1962 during geological mapping near
Sainte-Anne-de-la-Pocatière in Québec. It came from
mudstones within the Rivière-du-Loup
Formation. This formation was deposited in relatively
deep marine slope environments during the late Cambrian.
This represents quieter offshore conditions where
fine mud settled through the water column. These rocks have
received relatively little palaeontological attention,
making them ideal for reassessment.
The specimen
sat largely overlooked within the collections of the
Smithsonian National Museum of Natural History in Washington
DC for decades. This highlights one of the most important
aspects of palaeontology: major discoveries do not always
emerge directly from fieldwork.
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.
The
specimen sat largely overlooked within the collections of
the Smithsonian National Museum of Natural History in
Washington DC for decades.
Ajay
Suresh, CC
BY
More treasures awaiting
discovery
Our discovery adds to a growing body of
evidence that challenges the notion of a barren late
Cambrian world.
Studies from China
and Sweden
have documented other well-preserved fossils from about
497–485 million years ago.
Together, these
discoveries suggest ecosystems may have remained diverse and
ecologically complex during this time.
The new
Québec fossil expands this picture geographically. Our
specimen demonstrates the ancient Appalachian margin of
eastern Laurentia, the ancient continent that included much
of present-day North America and Greenland, was a site of
excellent fossil preservation.
This broadens the
known distribution of soft-bodied fossil preservation during
the interval. It also hints that comparable deposits may
await discovery elsewhere.
The Furongian gap
therefore may not represent a biological collapse at all.
Instead, it may partly reflect an “anthropogenic bias”
in the fossil record – a distortion introduced by where
humans have searched, collected, and studied fossils.
Each newly discovered Furongian exceptional fossil
site narrows this supposed gap. They reveal increasingly
sophisticated ecosystems thriving during the late
Cambrian.
Entire groups of organisms – and
possibly even ecosystems – may still await discovery
within museum drawers or poorly studied rock formations. The
late Cambrian lasted millions of years across vast ancient
oceans. Yet only a tiny fraction of its environments have
been systematically explored for soft-bodied preservation.
The next major fossil discovery may not come from
a newly discovered outcrop in a remote desert. It may
already exist, inside a museum cabinet, collected decades
ago and waiting for someone to recognise its
significance.
Russell
Dean Christopher Bicknell, Post-doctoral researcher in
Palaeobiology, Flinders
University and Julien
Kimmig, Head of Palaeontology Division at the Natural
History Museum Karlsruhe
This article is
republished from The
Conversation under a Creative Commons license. Read the
original
article.