This is Mazon Monday post #58. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Arthropleura is a genus of extinct millipedes. Their size ranged from about 0.3 meters to about 2.5 meters long. They are the largest known land invertebrates. Fossils are known from North America and Scotland, and are thought to have lived during the Carboniferous Period through to the early Permian Period (345 to 295 million years ago). At one time, Arthropleura was thought to an active predator, but due to the lack of preserved mouths, which could be an indicator that their mouth parts were not powerful and strongly sclerotized, it is now generally believed that they were herbivorous like modern millipedes. Arthropleura fossils have been found in the Mazon Creek deposit, no whole animals, just parts.
"Creature Corner" had a good page describing what has been found.
Arthropleura (millipede-like)
"The invertebrates are, on the whole, rather inconspicuous animals, --.
- Dr. E. S. Richardson, 1954
Thus did Dr. Richardson, over 30 years ago, begin an article describing a specimen found at Pit 11: it was a portion of the first arthropleurid found in North America.
Arthropleurids are millipede-like animals. One worker states "They resemble huge sow bugs. They also resemble trilobites in the trilobed structure of their numerous segments. These characteristics have seen the arthropleurids placed among the Myriapoda in a separate class, also in a separate Phylum, Trilobitomorpha. No truly complete specimen has been found. Reconstruction of the animal by various workers, produces an animal that has between 20 to 30 limb-bearing segments. Arthropleura Reconstruction. Head and tail reconstructions are tentative. Body sizes range from 30 mm (1.2 inches) to almost 2 meters (6 feet)! The giant among arthropodous animals.
Our creature was first described from a specimen discovered during the last century in the Saar Basin coalfields. Subsequently, portions of these animals have been found in France, Germany, Scotland, Canada and the United States. Earliest known arthropleurid is Eoarthropleura devonica from the Devonian of Aiken, Germany. Arthropluerids from the Carboniferous are given the generic name Arthropluera.
What is of interest is that their presumed trackways, the inchnogenus Diplichnites, have been discovered in Scotland, France, eastern Canada and Pennsylvania. Trackway widths in Canada and Scotland reached 36 cm (14 inches). Can you envision the animal that made these tracks winding its way through the Coal Age forest -- and wind its way it did. The curved trackways reveal an articulated animal, capable of maneuvering around obstacles. The trackways also show the animal to be terrestrial rather than aquatic. Trails were made in strata that eventually became laminated, silty sandstone and siltstone (originally sticky mud) material that was laid down during sheet floods. Our creature presumably walked through a "forest" growing along an alluvial fan in search of food. Arthropleura is considered to have been a vegetarian since fossils of this animal have been found with lycopod fragments in the gut area. A terrestrial animal of this size must have been a choice "prize" for the amphibians and mammal-like reptiles that were contemporaneous with Arthropleura.
Workers have made tests of various modern insects, myriapods and crustaceans traveling over smoked glass, powder, etc. Trackways made by the modern myriapods in these tests, especially the patterns made in "cornering", are so similar to the trackways of Arthropleura that many workers place our Creature among the Myriapoda, a view objected to by others.
Andrew A. Hay
The "Richardson's Guide to the Fossil Fauna of Mazon Creek" mentions find by Eugene Richardson shown in the specimens below.
Arthropleura cristata Richardson
Richardson (1956) was the first to accurately describe specimens of Arthropleura from Mazon Creek. Later (1959), he named a new species, A. cristata, designating a specimen consisting of the dorsal surface of a single paratergal fold (lat eral part of a tergite) as the holotype. This very large species is characterized by a row of large spines near the back border of the paratergal fold accompanied by a row of smaller spines even nearer to the border, and other characters. This rare form is found within the Braidwood fauna. Although there have been a number of good papers (e.g., Rolfe, 1969; Hahn et al., 1986) on arthropleurids, there has been little subsequent work on the classification of arthropleurids from Mazon Creek since Richardson's work. Most specimens from Mazon Creek consist of isolated limb fragments and rosette plates.
The flattened body form of Arthropleura and the layers of lycopod tree debris sometimes found fossilized in its guts suggest a life in the surface layers of litter along the forest floor, bur rowing within the rotting trunks of lycopod trees (Rolfe, 1980, 1985). However, trace fossils made by these large beasts indicate that they could roam about sandy areas as well (Rolfe, 1985; Briggs et al., 1984).
Arthropleura appears in "The Mazon Creek Fossil Fauna" by Jack Wittry. There's a good discussion, which notes that the contents of some suspiciously large coprolites might have belonged to Arthropleura.
Myriapods are among certain groups of animals that evolved giants at one time or another. Several species of Arthropleura grew to a length of two meters and are the largest known terrestrial arthropods of all. This enormous creature is also the largest known land animal in the Mazon Creek Biota and, in most locations, only pieces have been found. Concretions containing body parts-one or two segments, isolated limbs, rosette plates-are the rule. This genus differs from all other myriapods (and other arthropods) in the large number of segments per leg and in its unique rosette plate: a problematical plate-like structure developed at the base of the leg showing a complex pattern of grooved and raised areas. Trackways and trails of this animal have been found, disproving the early belief that it was aquatic. We now know what it ate; the gut contents found in fossils from other regions show that Arthropleura had a diet which at least in part consisted of lycopsid spores. In Mazon Creek fossils there is another bit of circumstantial evidence: unusually big coprolites have been found containing large amounts of broken-up lycopsid cone bracts.
Specimens
Found by Eugene Richardson and George Langford in 1952
Found by John L. McLuckie in 1953
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