450-million-year-old spider relative fossil found in fool's gold

A newly discovered fossil arthropod dating back 450 million years offers remarkable insights into the evolution of ancient creatures, according to a study published in the journal Current Biology. The species, named Lomankus edgecombei, was unearthed at the famous Beecher's Trilobite Bed in New York State, a site renowned for its exceptional preservation conditions that have yielded fossils with intricate details.

Lomankus edgecombei is a distant relative of modern-day horseshoe crabs, scorpions, and spiders. Belonging to the extinct class of predatory arthropods known as megacheirans, this discovery demonstrates that this group was still evolving 450 million years ago. Megacheirans thrived during the Cambrian Period (538-485 million years ago) and had mostly gone extinct by the Ordovician Period (485-443 million years ago). The finding of

Lomankus edgecombei adds a valuable piece to the puzzle of arthropod evolution.The fossil is preserved in three dimensions due to a unique natural process involving iron pyrite, also known as 'fool's gold', which infiltrated the remains after the animal's death. The iron pyrite occupied the cavities and replicated the animal's forms, resulting in exceptional golden shine preservation. This process is due to specific conditions of low oxygen and rich iron content at the Beecher's Trilobite Bed. Luke Parry, an Associate Professor of Paleobiology at the University of Oxford and lead author of the study, began examining the fossils when he was a postdoctoral researcher at the Yale Peabody Museum. He was "astonished" at how well

"In addition to their beautiful and striking golden color, these fossils are spectacularly preserved; it seems as if by washing the rock they come to life and flee," Parry said, according to El Cronista. He added, "They look as if they could just get up and scuttle away." The exceptional preservation allowed scientists to study the anatomy of Lomankus edgecombei in unprecedented detail.

Beecher's Trilobite Bed has a large representation of fossil organisms in perfect condition because iron pyrite maintained the shape of their bodies after being buried in sediment. The low-oxygen environment in which Lomankus edgecombei lived allowed pyrite to rapidly replace its delicate anatomical features before they decayed. Luke Parry explained that pyrite forms through the action of sulfate-reducing bacteria that break down organic material in the absence of oxygen, producing hydrogen sulfide, which can then react with iron to form pyrite.

The anatomy of Lomankus edgecombei offers insights into how the appendages on the heads of arthropods changed into the antennae, pincers, and fangs seen on insects, crustaceans, and arachnids today. Megacheirans, including Lomankus edgecombei were characterized by a large frontal appendage used to capture prey. However, Lomankus had a unique adaptation: its appendages featured three long, flexible whip-like flagella. These features are similar to living arthropods, suggesting the great appendage is the equivalent of the antennae of insects and the mouths of spiders and scorpions.

Lomankus edgecombei used its front appendage to perceive the environment rather than to capture prey, indicating a very different lifestyle from its older Cambrian relatives, who used their appendages to capture prey. This suggests that Lomankus edgecombei probably relied on its frontal appendage to sense and search for food in its dark, low-oxygen habitat.

The exceptional preservation process resulted in spectacular golden fossils in three dimensions that can be scanned to reveal hidden details about their anatomy. Due to the density of the pyrite, researchers had to employ advanced techniques like computed tomography to explore the anatomical details of

Lomankus edgecombei. Computed tomography involves rotating the specimen to take thousands of X-ray images that allow reconstructing the fossil in three dimensions.

Luke Parry said, "We get an almost complete look at their anatomy," according to The Independent. The specimens of Lomankus edgecombei were buried alive in turbidites, ensuring rapid burial without decomposition, likely due to huge dumps of sediment carried by turbidity currents. These turbidity currents created special conditions that allowed the arthropods to be pyritized from the outside in.

Co-corresponding author Professor Yu Liu from Yunnan University, China, 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," as reported by The Independent. The arrangement of features on Lomankus edgecombei's head was similar to that of living arthropods, suggesting evolutionary connections.

Greg Edgecombe, from the Natural History Museum in London, is considered one of the world's leading experts on arthropods. The new species honors him in its naming. The study confirms the importance of this discovery for the scientific community.

Steve Brusatte, a professor of paleontology and evolution at the University of Edinburgh's School of GeoSciences, said Lomankus edgecombei is an extraordinary find. "It's remarkable, like the whole body of this little arthropod has turned into a golden piece of jewelry," he said, according to Science. "And that makes the fossil not only beautiful, but scientifically important."

The finding of Lomankus edgecombei offers valuable clues to better understand how arthropods developed front appendages to control their environment and capture prey. These well-preserved fossils give new insight into the anatomy of megacheirans and help prove how arthropods developed their appendages.

Today, there are more species of arthropod than any other group of animals on Earth," Luke Parry said, as reported by Science. "Part of the key to this success is their highly adaptable head and its appendages, that have adapted to various challenges like a biological Swiss army knife."

Thanks to these exceptional discoveries, we can continue to learn about the evolution of life in ancient oceans and the anatomical features preserved so delicately. The fossil offers a portal into the natural world 450 million years ago, providing clues about what life on Earth looked like during that time.

Sources: Popular Science, Cosmos, Discover Magazine, El Nuevo Día, The Independent, Mundo Deportivo, Milenio.com, Scienze Notizie, Yahoo News, Science, ScienceAlert, El Cronista

This article was written in collaboration with generative AI company Alchemiq