A rare and stunning discovery in New York State has unveiled a 450-million-year-old fossil that provides valuable insights into the evolutionary path of arthropods.

This remarkable specimen, named Lomankus edgecombei, is a new species that belongs to the extinct class of Megacheirans, known for their large, clawed appendages used for grabbing prey.

A Rare Find: The Golden Fossil

Unlike the typical fossils that form through the gradual hardening of minerals around organic material, Lomankus edgecombei was preserved in a much rarer and striking way. Its body was replaced by pyrite, also known as fool’s gold.

This unique form of preservation is known as pyritization, and it allows the intricate details of the creature to be preserved in three-dimensional clarity.

The fossils were found in the Beecher’s Trilobite Bed, a Lagerstätte site well known for its exceptional preservation of ancient organisms. Lagerstätten sites are incredibly rare and offer an exceptional window into the distant past, where fossils remain so well-preserved that they seem almost alive.

The Role of Pyritization in Fossil Preservation

Pyritization is a rare preservation process that occurs when organic material is broken down in an oxygen-free environment by sulfate-reducing bacteria. These bacteria produce hydrogen sulfide, which reacts with iron in the surrounding sediment to form pyrite.

“Pyrite forms today through the action of sulfate-reducing bacteria that break down organic material in the absence of oxygen and produce hydrogen sulfide,” explains Luke Parry, a paleobiologist.

In the case of Lomankus edgecombei, this process allowed its anatomy to remain remarkably intact. The pyrite preserved its fine structures, providing a clear view of the animal’s body that would have otherwise been lost.

A Glimpse Into Arthropod Evolution

The discovery of Lomankus edgecombei is significant not only for its preservation but also for the insight it provides into the evolution of arthropods. Lomankus edgecombei belonged to the Megacheiran class, a group of arthropods that were abundant during the Cambrian period.

However, by the early Ordovician period, Megacheirans were in decline, making L. edgecombei one of the last surviving species from this group.

The fossil reveals that the front appendages, once used for prey capture in other Megacheirans, had undergone a significant transformation in L. edgecombei. These appendages, known as “great appendages,” had become much smaller and appeared to serve a different function.

A Window Into the Past

This reminder of the importance of exceptional fossil finds in unraveling the history of life on Earth. The pyritized fossils from Beecher’s Trilobite Bed offer an unparalleled opportunity to study ancient organisms in great detail, revealing insights into their biology and evolutionary history.

The exceptional preservation of Lomankus edgecombei highlights how the study of ancient life can provide valuable insights into the evolutionary processes that have shaped the diversity of life we see today.

Through careful analysis of these fossils, scientists can trace the steps of evolution that led to the development of modern arthropods.

Evolutionary Significance of Megacheirans

The Megacheirans were a dominant class of arthropods during the Cambrian period, with a wide range of species using their large appendages to capture prey. However, the decline of the Megacheirans by the early Ordovician marked the end of an era.

The discovery of Lomankus edgecombei offers a glimpse into the final stages of their evolutionary history. The species’ anatomical changes suggest that even as the group was declining, it was still evolving, adapting its appendages for new functions.

 “Lomankus shows us that megacheirans continued to diversify and evolve long after the Cambrian, with the formerly fearsome great appendage now performing a totally different function,” added Parry.

Today, arthropods are the most diverse group of animals on Earth, with their appendages evolving to serve a variety of functions in insects, arachnids, and crustaceans.