Mazon Creek Lamprey Fossil

Mayomyzon pieckoensis

Superclass Agnatha, Order Petromyzontiformes, Extinct Family Mayomyzontidae

Geological Time: Pennsylvanian (~300 m.y.a.)

Size: 43 mm across on a 73 mm by 48 mm nodule pair

Fossil Site: Mazon Ceek Pit 11, Francis Creek Shale, Braidwood, Illinois

Mayomyzon pieckoensisDescription: The Mazon Creek deposits of the region near Braidwood, Illinois rival the other famous Lagerstatten of the Burgess Shale, Solnhofen, and Liaoning for the variety of detailed life preserved. Many exquisitely preserved specimens are found in the ironstone nodules that make up the deposits. The majority of collecting areas are the spoil heaps of abandoned coal mines, the Mayomyzon pieckoensis most famous of which is Peabody Coal Pit 11. Pit 11 now serves as a cooling pond for the Braidwood nuclear power plant, but with over 100 other localities, specimens still come to light. This fossil exemplifies the exquisite preservation often seem in the Paleozoic Mazon Creek fossils.

This jawless fish is rarely seen; an extinct relative of the modern-day lampreys of the Family Petromyzontidae. Since there is no bony tissue, preservation was difficult. Notice the presence of myomeres, the longitudinal series of muscle fibers. Lacking mineralized tissues such as bone or calcified cartilage, lampreys are seldom preserved as fossils. In fact, other than an example from the Mississippian Bear Gulch fauna, and a recently discovered early Cretaceous example from Inner Mongolia, this is the only fossil lamprey known.

click fossil pictures to enlarge

Lamprey attched to fish
Below Lamprey Illustration - Above Attached to Ray-Finned Fish

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