Mississippian Bear Gulch Living Fossil Lingula and Oyster Assemblage

Description: 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 is an inarticulate brachiopod of the genus Lingula from the Mississippian of Montana. The genus is colloquially termed a “living fossil” by virtue of the fact that it has been in existence since the Ordovician some 450 million years ago, and persists today. Note the presence of another shellfish underneath the one brachiopod, and oyster of indeterminate genus. To round out this fine association piece we also have two fragments of the sponge Arborispongia (see my other listings for more complete examples).