RARE Gravid Terrasiid Mississippian Bear Gulch Fossil Fish

Apholodotus (Apholodotos) osna

Class Actinoptergyii, Order Terrasiiformes, Family Terrasiidae

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

Size: Fish fossil: 108 mm long (tip of nose to tip of tail along backbone) on a 243 mm by 180 mm and 275 mm by 240 mm matrix

Fossil Site: Heath Shale Formation, Bear Gulch Limestone, Fergus County, Montana

Apholodotus Bear Gulch Fossil FishDescription: 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 fine specimen is an example of an unusual fish known as Apholodotus osna with a narrow blade-like shape. Modern fishes of such morphology are often inhabitants of extremely weedy, sheltered environments. Locomotion is by undulation of the continuous dorsal/caudal/ventral fin complex, and can be used for both forward and backward movement. This one is believed to have been a burrower as specimens have been found in what are presumed to have been burrows. Note that this one is a gravid female; the body cavity is filled with roe, indicating that this one was overcome prior to spawning. This is a PRISTINE example, with NO RESTORATION.

Also see: Bear Gulch Paleozoic Fish Bear Gulch Fossils

Reference: Frickhinger, F. A., Fossil Atlas Fishes, 1995, p.327

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