A specimen of the new scorpion
species Eramoscorpius brucensis, which lived about 430 million years
ago, making it among the earliest scorpions.
The species probably lived
in water, but it had feet that would have allowed it to scuttle about on
A new scorpion species found fossilized in the rocks of a
backyard could turn the scientific understanding of these stinging
creatures on its head.
The fossils suggest that ancient scorpions crawled
out of the seas and onto land earlier than thought, according to the
researchers who analyzed them. In fact, some of the oldest scorpions had
the equipment needed to walk out of their watery habitats
and onto land, the researchers said. The fossils date back some 430
million to 433 million years, which makes them only slightly younger
than the oldest known scorpions, which lived between 433 million and 438
million years ago.
The new species "is really important, because
the combination of its features don't appear in any other known
scorpion," said study leader Janet Waddington, an assistant curator of
paleontology at the Royal Ontario Museum in Toronto.
Backyard fossils
The new species fell into Waddington's hands almost by happenstance.
Museum curators frequently get calls about fossils, most of which are
run-of-the-mill, she told Live Science. But a woman who called about an
"insect" in her backyard stone wall had something very exciting on her
hands.
"When she showed me this fossil, I just about fell on the floor, it was so amazing," Waddington said.
The fossil was no insect, but rather a scorpion
— and a new species at that. Over the years, more specimens trickled
in, mostly from patio stones and rock quarries, and one from a
mislabeled fossil at a national park on Canada's Bruce Peninsula. Now,
Waddington and her team have 11 examples of the new species, ranging in
length from 1.1 inches (29 millimeters) to 6.5 inches (165 millimeters).
What made the animal, dubbed
Eramoscorpius brucensis, so fascinating was its legs.
Walking in water
Previously, the earliest scorpion fossils found came from rocks that
were originally deposited in the water, leading paleontologists to
believe that the animals evolved on the seafloor, like crabs, and only
later became landlubbers. Ancient scorpions had legs like crabs, with a
tarsus, or foot segment, that was longer than the segment preceding it.
This arrangement, Waddington said, would have meant the creatures walked
on their "tippy-toes," such as crabs do today.
But
E. brucensis
was different. This species had a tarsus segment that was shorter than
the segment before it, which would have made it possible for the animal
to set its tarsus flat against the ground. In other words, this scorpion
had feet.
"They could have walked on their feet, which is really
important because it meant that they could have supported their own
weight," Waddington said. Without the need for water to buoy them up,
the animals could have walked on land.
The fossils also show that the scorpions' legs were solidly attached at
the body, without the exaggerated "hinge" seen in scorpions that would
have needed water to stay upright. What's weird, Waddington said, is
that all the other features of these scorpions seem aquatic. They are
found in marine rocks, and their digestive systems appear to require
water (in today's land scorpions, digestion begins outside of their
bodies, a process that requires adaptations these ancient scorpions lack).
Waddington said she and her team suspect that the fossils they've
collected are not the bodies of dead scorpions at all. Instead, they may
be molts, exoskeletons left behind as the scorpions grow. Scorpions are
incredibly vulnerable during molting, Waddington said, and in deep
water, ancient squidlike animals would have loved a helpless scorpion
snack. The scorpions that could haul themselves out of the water onto
the shore to escape predators would have had a survival advantage. The
rocks that house the scorpion fossils often feature ripples that would
have been created when wind blew thin films of water over land,
suggesting a shoreline lagoon habitat.
What that means is that the first adaptations that scorpions developed
for life on land could have appeared much earlier than researchers
thought.
"Our guys are really, really old," Waddington said. "They're vying for the second-oldest [scorpions] known."
The researchers reported their findings today (Jan. 13) in the journal Biology Letters.
