Scientists discover ancient spiny-legged arachnid: A peek into Earth’s distant past

Fossilized Douglassarachne acanthopoda, noted for its up-armored spiny legs, might have resemblance to modern harvestmen spiders, but with a more experimental body plan. Credit: Paul Selden.

Over 300 million years ago, strange and diverse arachnids roamed the Carboniferous coal forests of North America and Europe.

These ancient forests were home to spiders, scorpions, harvestmen, and more exotic creatures like whip spiders and whip scorpions.

Among these, a unique arachnid with spiny legs has recently been discovered.

This fascinating arachnid, named Douglassarachne acanthopoda, was found in the famous Mazon Creek fossil site in Illinois.

This creature lived about 308 million years ago and measured around 1.5 centimeters in body length.

Its most striking feature is its robust, spiny legs, making it quite different from any other known arachnid, whether living or extinct.

Paul Selden from the University of Kansas and the Natural History Museum of London, along with Jason Dunlop from the Museum für Naturkunde Berlin, co-wrote a paper describing this discovery in the Journal of Paleontology.

According to Selden, the Carboniferous Coal Measures are a crucial source of information about ancient arachnids.

This period marks the first time most living groups of arachnids coexisted, although their variety was different from what we see today.

Back then, spiders were a rare group, consisting mainly of primitive lineages. They shared their habitat with various arachnids that have since gone extinct.

Dunlop noted that Douglassarachne acanthopoda is an impressive example of these extinct species. Its spiny legs resemble those of modern harvestmen, but its body structure is unlike any known arachnid group.

The scientists found it challenging to determine Douglassarachne acanthopoda’s exact relatives due to missing details like mouth parts. It might belong to a broader group that includes spiders, whip spiders, and whip scorpions.

This discovery suggests that ancient arachnids experimented with different body plans, some of which became extinct, possibly during the “Carboniferous Rainforest Collapse.”

This period, shortly after the age of Mazon Creek, saw coal forests fragmenting and dying off. Alternatively, these strange arachnids might have survived until the end-Permian mass extinction.

The Mazon Creek fossil site is one of the most significant windows into life during the late Carboniferous period.

It has produced a wide range of fascinating plants and animals. The Douglassarachne acanthopoda fossil was found in a clay-ironstone concretion in the 1980s by Bob Masek and later acquired by the David and Sandra Douglass Collection.

The Douglass family donated the specimen to the Field Museum of Natural History in Chicago for scientific study once it was recognized as a new species.

The name Douglassarachne honors the Douglass family, and acanthopoda refers to the arachnid’s unique spiny legs.