Paratarrasius Mississippian Bear Gulch Fish Fossil
Rare Museum Fossil Fish
Time: Mississippian (~320 m.y.a.)
mm = 1 inch): Fish fossil is 120 mm long (tip of nose to tip of tail
along backbone) on a 250 mm by 170 mm matrix
Heath Shale Formation, Bear Gulch Limestone, Fergus County, Montana
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.
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,
to enlarge fossil pictures