Rudy Lerosey-Aubril
Modern spider with the fossil Megachelicerax cousteaui
The discovery of a new fossil indicates that chelicerates existed about 20 million years earlier than previously thought.
A new study published in the journal Nature is reshaping scientists’ understanding of the early evolution of spiders.
When examining a fossil of an arthropod from the Cambrian period, 500 million years old, researcher Rudy Lerosey-Aubril, from Harvard University, noticed something unusual: a claw positioned where an antenna should be.
Upon closer inspection, the scientist realized he had discovered the oldest known chelicerae. The chelicera is a pincer-shaped appendage that distinguishes spiders, scorpions, and related species from other arthropods.
The newly identified species, Megachelicerax cousteauiwas named in honor of the famous ocean explorer Jacques Cousteauwhose work has inspired generations to explore marine life. The fossil provides crucial information about the early evolution of chelicerates, an important group of arthropods that includes more than 120,000 species alive today, explains .
Lerosey-Aubril spent more than 50 hours carefully preparing the fossil under a microscope, using a fine needle to reveal its delicate structures. The specimen shows a cephalic shield attached to nine body segmentsalong with six pairs of specialized appendages for feeding. Its lower part also has respiratory structures similar to the foliaceous gills found in modern horseshoe crabs.
However, the most significant feature is the chelicera itself. Previously, no fossils from the Cambrian period had shown evidence of this fundamental feature. The discovery anticipates the known origin of chelicerates in about 20 million yearspredating previous records from the Ordovician period.
The fossil also helps resolve long-standing debates about how chelicerates evolved by indicating that their characteristic body plan, including specialized cephalic appendages and segmented body regions, developed earlier than previously thought.
