Douglassarachne acanthopoda: The Mysterious Spiny Arachnid of the Past
Douglassarachne acanthopoda, a 308-million-year-old spiny fossil, challenges the classification of ancient arachnids. Discovered in Mazon Creek, Illinois, it represents a crucial era in the history of arachnids.
The long and spiny individual we are about to present to you is Douglassarachne acanthopoda, but for convenience we will call him Doug. We're joking :) At first glance, you might think it's just a spider, but wait a minute! This fossilized specimen, although it shares many characteristics of modern arachnids, has traits so unique that paleontologists have trouble classifying it.
Spiders and their ancestors have populated our planet for approximately 400 million years. If we traveled back in time to the Carboniferous and found ourselves in the coal forests of North America or Europe, we might recognize creatures similar to spiders, opilionids, or scorpions. However, even in that context, Douglassarachne acanthopoda would stand out.
“Douglassarachne acanthopoda was found at the famous Mazon Creek locality in Illinois and has an estimated age of approximately 308 million years,” said Paul Selden, lead author of a study on this enigmatic fossil. This compact arachnid measured about 1.5 centimeters in length and was distinguished by its sturdy, spiny legs, making it completely different from any other known arachnid, both living and extinct.
This fossil's extremely spiny legs are reminiscent of some modern opilionids, but its body structure is very different from that of an opilion or any other known group of arachnids, as Jason Dunlop, a co-author of the study, explained. The lack of details, such as clear mouthparts, typical of such an ancient fossil, makes precise classification difficult.
The period in which Douglassarachne acanthopoda lived is considered crucial to the history of arachnid, as it represents a time when many arachnid species shared the same environment. The Mazon Creek location, where this fossil was discovered in the 1980s, is an important landmark for understanding this period.
Despite uncertainties about its evolutionary affinities, it appears that these spiny arachnids come from a time when arachnids were experimenting with different body structures, some of which later disappeared, perhaps during the “Carboniferous rainforest collapse” or perhaps persisting until to the great Permian mass extinction.
Although the classification of this fossil was problematic, it was necessary to give it a scientific name. The Douglassarachne genus is a tribute to the Douglass family, who donated the specimen to the Field Museum of Natural History in Chicago for scientific study once it was clear that it represented an yet undescribed species. The term “acanthopoda” refers to the animal's unique, spiny legs.
Nowadays, spiders seem to be everywhere on our planet, but in the past they were a rarer presence. Their ancestors shared the environment with many other impressive, now extinct creatures, the diversity of which we can only imagine thanks to fossils. Douglassarachne acanthopoda represents an extraordinary example of these extinct forms, as Jason Dunlop points out.
The study on this fascinating fossil was published in the Journal of Paleontology (https://www.cambridge.org/core/journals/journal-of-paleontology/article/remarkable-spiny-arachnid-from-the-pennsylvanian-mazon-creek-lagerstatte-illinois/0E1B32BAFCAEA067018EF9BF349F8B81) and represents an important contribution to our understanding of the evolution of arachnids.
