Cardiosuctor, A Mississippian Bear Gulch Coelacanth

Cardiosuctor populosum

Class Sarcopterygii, Subclass Coelacanthimorpha, Order Coelacanthiformes, Family Rhabdodermatidae

Geological Time: Mississippian (~320 m.y.a.)

Size: 198 mm

Fossil Site: Taylor Formation, Bear Gulch Limestone, Fergus County, Montana

Cardiosuctor populosumDescription: The Bear Gulch Limestone is a deposit of some 70 square km in extent and 30 m in depth that has been a source of one of the most diverse assemblages of fossil fish with some 110 species having been described over the past 30 years. Most were new to science, and provided a unique view of the marine environment of Mississippian times. Fine preservation of both fish and invertebrates is a hallmark of these deposits, presumably due to an anoxic depositional environment. This specimen is a coelacanth known as Cardioscuctor, and is well-represented in the Bear Gulch deposits. Specimens found range from 30 mm to 250 mm. They exhibit sexual dimorphism, with larger, more robust females and smaller, more gracile males, a condition found in the modern coelacanth Latimeria. The species died out in the Lower Carboniferous.

click to enlarge fossil pictures


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