This is Mazon Monday post #28. What's your favorite Mazon Creek fossil? Tell us at email:[email protected].
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Today, we have a species spotlight on Cyclus americanus. It's one of my favorite Mazon Creek animals. Cycloids form an order of fossil arthropods that lived from the Carboniferous to the Cretaceous periods.
Here is the text from the Creature Corner column, which was published in March 1987.
Cyclus americanus (crustacean)
Cyclus is indeed a most "vexing animal". Discovered as a fossil in Europe in 1836, it was classified among the trilobites. In ensuing years, the Carboniferous limestones and ironstones of Europe yielded several more specimens. Cyclus was discovered in an ironstone nodule at Morris, llinois 45 years later, named species -americanus.
A short chronology will explain the opening sentence.
- 1836 Cyclus discovered labeled a Trilobite
- 1884/5 Cyclus discovered at Morris, described and labeled limulid/Xiphosuran ("horseshoe crab")
- 1894 Numerous species studied; "suckers" described on Cyclus.
- 1902 Cyclids discovered in Pn. Limestone at Kansas City, Missouri
- 1925 Cyclidae described. Cyclus classified with the Branchiura - "fish lice".
Most recently Cyclus is classified thus - Subphylum: Crustacea; Class: Maxillopoda; Subclass: Branchiura; Order: ? (F. Schram personal communication).
A quick field identification of Cyclus - if it looks like an apple hanging from a twig, it's Cyclus. Straight, bar-like antennae at 90 degrees to the center line of the circular body, give it the appearance of a hanging object. The six pairs of "legs" and the telson (tail) are not always visible on the fossil specimens. Location of the eyes is a matter for conjecture. A circular, low profile carapace is the shape of an animal living in a swift water environment. As noted by early workers,Carboniferous swamps are not envisioned as swift water environments. Discovery of "suckers" on the animal, coupled with body shape, led to the conclusion it may have been a parasite. Hence the "fish lice designation. Despite the fine preservation of certain Mazon Creek/Pit 11 Cyclus americanus, details of body parts are difficult to discern.
Mazon Creek/Pit 11 is the location for Cyclus americanus. The Cyclids found at Kansas City are of a different species.
Here is the text from book "The Mazon Creek Fossil Fauna" by Jack Wittry.
Cycloids are an extinct group which wan first discovered in Europe in 1835 and assigned to the trilobites. Originally described from European specimens as a horseshoe crab by Packard (1883), Cyclus americanus was first found in the Mazon Creek area in 1884 in a single concretion from Morris, Illinois. Later in 1925, this group was assigned by A. T. Hopwood to the group known commonly as Fish Lice. These efforts were just some in a long history of confusion over the affinities of these enigmatic arthropods. Due to the fact that several features are not yet fully understood, its closest. taxonomic relation still remains a mystery. At present, the evidence points to Cycloids most likely being a sister group to Copopods.
C. americanus is common in Essex animal concretions.A round body (about 15 mm in diameter) and long, straight antennae located on the anterior of the body give the fossil the appearance of an apple hanging from a twig. At the posterior, there is a distinct notch where a pair of short, stout, flipper-like processes are seen. Leg appendages are seldom visible, and no internal details are known. Schram believes they filled a crab-like niche in Paleozoic shallow seas. Other members of the Cycloids have since been discovered at other locations in North America and Europe.