The Bear Gulch Limestone (Mississippian of Montana) is what is known as a lagerstätte, a well-bedded sequence of limestone layers containing an extremely well-preserved assemblage of fossils. This deposit has yielded one of the most diverse and well preserved fossil fish assemblages in the world. We have excavated approximately 130 species of fish from this deposit over the last 35 years. The site also contains well preserved arthropods, sponges, starfish, conulariids, worms, and other soft-bodied organisms, as well as brachiopods, bryozoans, and molluscs. The Bear Gulch fossils are so well preserved that they provide a window into the life of the Mississippian that has never been available before. This site is dedicated to bringing you and the fishes of the Mississippian together.
The fish of the Bear Gulch Limestone include a lamprey, an acanthodian, over 65 species of "sharks", six coelacanths, a rhizodont, and a host of ray-finned bony fish. Most of these species had never been seen before by science and none had ever been seen intact before. Fossils are preserved along a spectrum that ranges from scattered scales to the extreme of beautiful sharks with their venous systems and skin pigments intact.
The Bear Gulch limestone is up to 90 feet thick and approximately 8 miles in east-west extent, and was deposited in a shallow, muddy, tropical marine bay 318 million years ago. The latitude of the bay was approximately 12° from the equator at the time of deposition. The climate of the surrounding area must have been seasonally quite arid, as there are gypsum beds in adjacent parts of the Heath Formation. Fish faunal diversity is high, while invertebrate diversity is only moderate. The high diversity of fish and the wide range of body forms is evidence of a complex ecosystem most similar to modern bay or estuarine communities.
Work (by Richard Lund and Eileen Grogan) continues on the descriptions of the fish and on understanding their relationships and ecology. Further fish and additional information will be added to this site as studies of them are completed.