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A sparkling ancient fossil discovered in New York state looks like a finely crafted piece of jewelry, but it’s also a portal to the natural world of 450 million years ago.
The striking fossil is a newly identified species of arthropod, a distant relative of modern-day horseshoe crabs, scorpions and spiders, which bears a slight resemblance to a modern-day shrimp. The creature lived on the ocean floor during the Ordovician period (485 million to 444 million years ago), a time when life had only a temporary foothold on land.
Named Lomankus edgecombei, the arthropod is a remarkably bright golden color because it is preserved in three dimensions by iron pyrite – a mineral better known as fool’s gold.
This is a very unusual way of forming a fossil.
The fossil, one of five similar specimens described in a paper published Tuesday in the journal Current Biology, was discovered in a fossil-rich area near Rome in central New York state known as from Beecher’s Bed.
The study’s lead author, Luke Parry, began examining the fossils while he was a postdoctoral researcher at the Yale Peabody Museum, where three of the specimens were housed. A collector donated two more specimens to Yu Liu, co-author and professor of paleobiology at Yunnan University in China. They are now also part of the Peabody collection.
Because pyrite was so dense, Parry was able to scan the fossil using CT to reveal hidden details of its anatomy. This discovery sheds light on why arthropods developed appendages protruding from their heads.
“I was pretty blown away by their state of preservation and having worked on pyritized burrows before I knew they would work really well on scanner,” said Parry, now an associate professor of paleobiology at the University of Oxford, by email. “Preservations in pyrite of this kind are extremely rare. Over the last half-billion years, there are only a handful of examples of places where this has happened.
Lomankus is an extraordinary discovery, said Steve Brusatte, professor of paleontology and evolution at the University of Edinburgh’s School of GeoSciences.
Brusatte, who was not involved in the study, said it was “one of the most breathtaking fossils I have ever seen.” It sparkles like gold and looks like it belongs in an art museum.
“Fool’s gold shows fine detail on many parts of this arthropod’s body, including the small, wispy sensory structures that protrude from its head,” he said. “Normally, such delicate, gossamer objects would be obliterated once an animal died and was buried, but here, the fool’s gold encased them in stone.”
The species, which belongs to an extinct group called megacheira, is named after arthropod expert Greg Edgecombe, a researcher at the Natural History Museum in London.
Other megacheirans used their appendages to capture prey. Lomankus, which had no eyes, likely used its appendages to sense the oceanic sedimentary environment in which it lived, according to the study.
The arrangement of features on the species’ head was similar to that of living arthropods, meaning its appendages are the ancient equivalent of insect antennae or the mouthparts of scorpions or spiders, Parry said.
Today, there are more known species of arthropods than any other group of animals on Earth. Parry said their adaptable head and appendages, which he described as a “biological Swiss army knife”, were one of the reasons the group had thrived for so long.
“Sometimes we see fossils preserved as opals or quartz crystals, or in this case, fool’s gold,” Brusatte said.
“It’s remarkable, as if the whole body of this little arthropod had transformed into a golden jewel,” he added. “And that makes the fossil not only beautiful, but also scientifically important.”
