Imma Perfetto
Cosmos science journalist
A spectacular golden fossil has been discovered preserved in iron pyrite, otherwise known as fool’s gold, in the US state of New York.
The new species, Lomankus edgecombei, was an arthropod – an animal with a hard exoskeleton. It is distantly related to today’s spiders, scorpions, insects, and crustaceans.
“As well as having their beautiful and striking golden colour, these fossils are spectacularly preserved,” says Associate Professor Luke Parry of the University of Oxford, UK, lead author of a paper describing the discovery in Current Biology.
“They look as if they could just get up and scuttle away.”
L. edgecombei belonged to the extinct class of predatory arthropods known as the megacherians. These animals are known for the large, modified legs on their heads known as “great appendages”, which were typically used to capture prey.
Megacheirans were very diverse during the Cambrian Period (538-485 million years ago) but were thought to be largely extinct by the Ordovician Period (485-443 million years ago). L. edgecombei dates to about 450 million years ago.
The low-oxygen environment in which it lived allowed pyrite to rapidly replace its delicate anatomical features before they decayed. Because pyrite is a very dense mineral, the researchers were then able to scan the fossil using micro-computed tomography (microCT) to reveal hidden details of its anatomy.
They found that, unlike earlier megacheirans, L. edgecombei had much smaller claws which ended in 3 long and flexible whip-like appendages. It also seems to have lacked eyes.
This suggests the animal relied on its frontal appendage to sense and search for food in the dark environment in which it lived, rather than to actively capture prey like the apex predators of the Cambrian period.
The new discovery offers important new clues towards solving an interesting question: what is the equivalent of the megacheirans’ great appendage in living species?
The researchers say that the arrangement of features in the L. edgecombei fossil is similar to living arthropods, suggesting the great appendage may be the equivalent of insects’ antennae and the chelicera (mouthparts) of spiders and scorpions.
“Today, there are more species of arthropod than any other group of animals on Earth,” says Parry.
“Part of the key to this success is their highly adaptable head and its appendages, that has adapted to various challenges like a biological Swiss army knife.”
