An ancient bug preserved in glittering fool’s gold

• Scientists analyzed a newly discovered fossilized bug species named Lomankus edgecombei, preserved in pyrite (fool’s gold). They found intricate details of its 450-million-year-old structure with 3D-imaging techniques.
• Lomankus edgecombei was a marine, eyeless arthropod. An arthropod is an invertebrate animal with a hard outer covering, jointed legs and a segmented body. This species likely lived in a dark, deep-sea habitat.
• The new analysis challenges previous beliefs about the extinction timeline of the group of arthropods it belongs to. The discovery shows they continued evolving into the Ordovician period, well after the Cambrian explosion.

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Meet the ancient bug Lomankus edgecombei

On October 29, 2024, scientists said they identified a new species of ancient bug from a fossil found in New York. This fossil is extraordinary because it was pristinely preserved in pyrite, otherwise known as fool’s gold. They named it Lomankus edgecombei, which means edge of a valley.

Lomankus edgecombei was a marine creature that lived 450 million years ago, back when New York State was submerged beneath the sea. It had no eyes. And it used small leg-like appendages next to its head to dig into ocean floor sediment in search of food.

This ancient bug was an arthropod. That’s a diverse group of animals that include present-day scorpions, spiders, horseshoe crabs and insects.

Moreover, it belongs to a sub-group of arthropods known as Megacheirans. These are extinct arthropods that had large, modified legs (called “great appendages” by scientists) near the head. Many, but not all, Megacheirans used those large legs to catch prey.

The researchers published their findings in the peer-reviewed journal Current Biology on October 29, 2024.

More details about this ancient bug

Like other Megacheirans, Lomankus also had large, modified legs near its head. But Lomankus was different. Its front legs were smaller in comparison to other Megacheirans. And its front leg tips had three long, whip-like structures. Its anatomy suggests Lomankus used its large front legs in sensing its environment, not for grabbing food.

Lomankus also did not have eyes. This, and its front leg structures for sensing its surroundings, indicates it lived in a dark environment.

Co-author Yu Liu of Yunnan University said:

These beautiful new fossils show a very clear plate on the underside of the head, associated with the mouth and flanked by the great appendages. This is a very similar arrangement to the head of Megacheirans from the early Cambrian of China except for the lack of eyes, suggesting that Lomankus probably lived in a deeper and darker niche than its Cambrian relatives.

Lomankus in the fossil record timeline

Megacheirans emerged and widely diversified during the Cambrian Period (541 to 485 million years ago), a period noted for an explosion in the diversity of life on Earth. But scientists thought many Megacheirans were extinct by the beginning of the Ordovician Period (485 to 443 million years ago).

However, Lomankus, dated at 450 million years old, indicates that Megacheirans continued to evolve longer than scientists previously thought.

Lead author Luke Parry of the University of Oxford remarked:

As well as having their beautiful and striking golden color, these fossils are spectacularly preserved. They look as if they could just get up and scuttle away. Rather than representing a “dead end,” Lomankus shows us that Megacheirans continued to diversify and evolve long after the Cambrian.

How this golden fossil came to be

Lomankus was found near Rome, New York, in a location called Beecher’s Bed, which is rich in fossils such as trilobites (extinct bug-like creatures distantly related to horseshoe crabs). The animals had been rapidly buried in a low-oxygen environment. That significantly slowed decomposition, allowing minerals to replace its body parts.

Lomankus was buried in sediment rich in sulfate and iron. As a result, pyrite (a form of iron sulfide) replaced its body during fossilization. Since pyrite is a dense mineral, a micro-CT scan revealed details of Lomankus‘ body. Micro-CT stands for micro-computed tomography: It’s x-ray imaging from many angles to construct a detailed 3D view of a small object.

Co-author Derek Briggs of Yale University said:

These remarkable fossils show how rapid replacement of delicate anatomical features in pyrite before they decay, which is a signature feature of Beecher’s Bed, preserves critical evidence of the evolution of life in the oceans 450 million years ago.

The density of the pyrite contrasts with that of the mudstone in which they were buried. Their details were extracted based on computed tomography [CT] scanning, which gave us 3D images of the fossils.

Bottom line: Scientists analyzed a newly discovered fossilized bug species, 450 million years old, pristinely preserved in pyrite, or fool’s gold.

Source: A pyritized Ordovician leanchoiliid arthropod

Via Yale University

Via University of Oxford

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