This is Mazon Monday post #217. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
-----------------------------------------------------
Douglassarachne acanthopoda n. gen. n. sp., reconstruction of the possible appearance of the animal in life.
The world has a brand new Mazon Creek spider. Douglassarachne acanthopoda was originally found in the Pit 15 locality by Bob Masek in the 1980s. Bob (Earth Magazine article) has been a premier fossil preparator for many years, working on SUE and other important finds at the Field Museum. Later, he worked at the University of Chicago preparing fossils for Paul Sereno, among his contributions SuperCroc, Sarcosuchus. The fossil spider was later acquired by David and Sandra Douglass and displayed in their Prehistoric Life Museum in the basement of Dave's Down to Earth Rock Shop in Evanston, IL (Throwback Thursday #94 and TFF post by Ralph Jewell). Bob Masek and David and Sandra Douglass are all long time ESCONI members.
Douglassarachne acanthopoda was described in a new paper published in the Journal of Paleontology "A remarkable spiny arachnid from the Pennsylvanian Mazon Creek Lagerstätte, Illinois" by Paul A. Seldon (University of Kansas and the Natural History Museum of London) and Jason A. Dunlop (Museum für Naturkunde Berlin).
Abstract
A new genus and species of arachnid (Chelicerata: Arachnida), Douglassarachne acanthopoda n. gen. n. sp., is described from the late Carboniferous (Moscovian) Coal Measures of the Mazon Creek Lagerstätte, Illinois, USA. This is a unique animal with distinctive large spines on the legs. It has a subovate body, a segmented opisthosoma, and a terminal anal tubercle. The legs are robust and appear to have been similar in construction throughout the limb series, with heavy spination of the preserved proximal podomeres. The mouthparts and coxo-sternal region are equivocal. The preserved character combination does not permit easy referral to any known arachnid order, living or extinct, thus the new fossil in placed as Arachnida/Pantetrapulmonata incertae sedis. It contributes to an emerging pattern of disparate body plans among late Carboniferous arachnids, ranging from anatomically modern members of living orders through to extinct taxa, such as the present fossil, whose phylogenetic position remains unresolved.
UUID: http://zoobank.org/b70f5f95-9c8b-4389-bee5-b6031bff2ee2
Non-technical Summary
The forests of the late Carboniferous period (about 300–320 million years ago) harbored a great variety of arachnids. In addition to the familiar spiders, harvestmen, and scorpions, there were other, stranger kinds of spider-like animals. Here, we describe a large spider-like arachnid with very spiny legs (presumably to deter predators), from the world-famous Mazon Creek fossil localities of Illinois, USA.
Holotype
PE 91366, part and counterpart, donated from The David and Sandra Douglass Collection to The Field Museum of Natural History, Chicago, Illinois; Mazon Creek Lagerstätte, Francis Creek Shale Member of the Carbondale Formation (Desmoinesian), Pit 15 Northern Mine tip, near Essex, Kankakee County, Illinois (41.1525°N, 88.2275°W).
Description
Large arachnid with subovate body, length including anal tubercle ~15.4 mm. Carapace subtriangular in outline, length 5.2 mm, width 7.2 mm (ratio 0.73). Cephalic area subtrapezoidal, length 2.2 mm, width 3.0 mm (ratio 0.73), with curved anterior–lateral margin, straight posterior edge demarcated by line of tubercles; suboval raised region in median part of cephalic area bearing high point at anterior end (ocular tubercle?). Cephalic area finely tuberculate, lateral areas less so. Transverse line ~0.6 mm behind posterior edge of central area.
Acknowledgments
Most grateful thanks go to A. Young, the Douglass family, and The David and Sandra Douglass Collection for kindly allowing study of the specimen and depositing it at the Field Museum for posterity. We thank P. Mayer (FMNH) and the Field Museum for the loan of the specimen for research. Finally, we thank R. Garwood and L. Lustri for their helpful comments on the manuscript.
Press Release from Andrew Young
A remarkable spiny-legged arachnid from the coal forests of America
More than 300 million years ago, all sorts of arachnids crawled around in the Carboniferous coal forests of North America and Europe. These included familiar forms we would recognize today, such as spiders, harvestmen and scorpions, as well exotic animals which now occur in warmer regions such as whip spiders and whip scorpions. There were also some quite strange-looking arachnids in these habitats which belonged to groups that are now long extinct. One such fossil was recently described in a new paper published in the international science journal, Journal of Paleontology, co-authored by Paul Selden from the University of Kansas and the Natural History Museum of London and Jason Dunlop from the Museum für Naturkunde Berlin. Douglassarachne acanthopoda comes from the famous Mazon Creek locality in Illinois, USA, and is about 308 million years old. This compact arachnid has a body length of about 1.5 cm and is characterized by its remarkably robust and spiny legs, such that it is quite unlike any other arachnid known: living or extinct.
The Carboniferous Coal Measures are an important source of information for fossil arachnids, and represent the first time in Earth’s history when most of the living groups of arachnids occurred together. At the same time, the fauna was still quite different to today. Spiders were a rather rare group, only known at that time from primitive lineages, and they shared these ecosystems with various arachnids which have long since died out. Douglassarachne acanthopoda is a particularly impressive example of one of these extinct forms. The fossil’s very spiny legs are reminiscent of some modern harvestmen, but its body plan is quite different from a harvestman, or any other known arachnid group. This led the scientists to conclude that it does not belong in any of the known arachnid orders. Unfortunately, details such as the mouthparts cannot be seen, which makes it difficult to say exactly which group of arachnids are its closest relatives, but it could belong to a wider group which includes spiders, whip spiders and whip scorpions.
Whatever its evolutionary affinities, these spiny arachnids appear come from a time when arachnids were experimenting with a range of different body plans. Some of these later became extinct, perhaps during the so-called ‘Carboniferous Rainforest Collapse’, a time shortly after the age of Mazon Creek when the coal forests began to fragment and die off. Or perhaps these strange arachnids clung on until the end Permian mass extinction?
The Mazon Creek fossil locality is one of the most important windows into life in the Late Carboniferous, and has produced a wide range of fascinating plants and animals. The present fossil was discovered in a clay-ironstone concretion in the 1980s by Bob Masek and later acquired by the David and Sandra Douglass Collection and displayed in their Prehistoric Life Museum. The genus name Douglassarachne acknowledges the Douglass family, who kindly donated the specimen to the Field Museum of Natural History in Chicago for scientific study once it became apparent that it represented an undescribed species, while acanthopoda refers to the unique and characteristic spiny legs of the animal.
Reference
Selden, P. A. & Dunlop, J.A. 2024. A remarkable spiny arachnid from the Pennsylvanian Mazon Creek Lagerstätte, Illinois. Journal of Paleontology.
doi: 10.1017/jpa.2024.13
University of Kansas Press Release
The ancient critter recently was described in a new paper published in the Journal of Paleontology, co-written by Paul Selden from the University of Kansas and the Natural History Museum of London and Jason Dunlop from the Museum für Naturkunde Berlin.
“Douglassarachne acanthopoda comes from the famous Mazon Creek locality in Illinois and is about 308 million years old,” said lead author Selden. “This compact arachnid had a body length of about 1.5 centimeters and is characterized by its remarkably robust and spiny legs — such that it is quite unlike any other arachnid known, living or extinct.”
The KU researcher said Carboniferous Coal Measures are an important source of information for fossil arachnids, representing the first time in Earth’s history when most living groups of arachnids occurred together. Yet, the fauna was still quite different to today.
“Spiders were a rather rare group, only known at that time from primitive lineages, and they shared these ecosystems with various arachnids which have long since died out,” said co-author Dunlop. “Douglassarachne acanthopoda is a particularly impressive example of one of these extinct forms. The fossil’s very spiny legs are reminiscent of some modern harvestmen, but its body plan is quite different from a harvestman or any other known arachnid group.”
This led the two scientists to conclude it doesn’t belong in any of the known arachnid orders.
Photos
From the paper
Douglassarachne acanthopoda n. gen. n. sp., holotype and only known specimen FMNH PE 91366. (1) Photograph of part; (2) explanatory drawing of part; (3) photograph of counterpart; (4) explanatory drawing of counterpart; 1–4 = leg numbers; a t = anal tubercle; e t = eye tubercle; fe = femur; t = tergite. Scale bars = 5 mm.
from the Prehistoric Life Museum in the basement of Dave's Down to Earth Rock Shop in Evanston, IL (photo by Ralph Jewell)
