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 fine specimen is an example of an unusual fish Paratarassius hibbardi with a 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. The fin is quite readily seen in this fine large example.

References:
Lund, R., and W. G. Melton jr., 1982. "A new actinopterygian fish from the Mississippian Bear Gulch Limestone of Montana." Palaeontology 25: 485-498.
Lund, R., and C. Poplin. 2002. "Cladistic analysis of the relationships of the Tarrasiids (Lower Carboniferous Actinopterygians)." Journal of Vertebrate Paleontology 22 (3): pp480-486, Sept 2002.