Superb Mazon Creek Acanthodian Fossil Fish Acanthodes

Acanthodes sp

Infraphylum Gnathostomata, Class Acanthodii, Order Acanthodiformes

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

Size (25.4 mm = 1 inch): Fossil is 40 mm long; Matrix: 30 mm by 50 mm and 47 mm by 24 mm nodule pair

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

Code: HMC13

Price: $1595.00 - sold

Acanthodian Fossil Fish AcanthodesDescription: 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 most famous of which is AcanthodiiPeabody 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 one is of the fossil fish Acanthodes, preserved here in lateral aspect. Note the pigmented retinas, spines in the fins, and the tail fin. The Acanthodians are jaw-bearing fish who still are the subject of dispute over their systematic position. They possess highly-advanced, spindle-shaped bodies thought to have made them swift swimmers. The body was covered in small mosaic-like scales. They possessed small teeth which were typically confined to the lower jaw; some were toothless. The feature they all share in common is the fact that all fins other than the caudal are supported by massive spines formed of dentine. Indeed, the name Acanthodii is derived from the Greek word for spine. The oldest acanthodian lived during the late Ordovician. They reached their peak during the Devonian, and became extinct during the Great Dying of the end-Permian extinction. This is beyond a doubt the finest example I have ever come across.

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