Thursday, January 21, 2010

Endothyra baileyi Foraminifera

Foraminifera fossils from the Salem Limestone of Washington County, Indiana. These creatures are called Endothyra baileyi and existed 360-325 million years ago (Mississippian Period).  Microfossils were studied quite a bit by the oil exploration industry so they could determine the rock layers drills had reached to help find fossil fuels.  I am not sure if they have the same importance today with the proliferation of advanced sensing technology.

Endothyra baileyi foraminifera (Webster's dictionary: "marine protozoans with calcareous shells full of tiny holes through which slender filaments project") described by James Hall in Transactions Albany Institute, volume IV, page 34 published in 1856.  The description is "Shell depressed, orbicular, sub-equally convex above and below, smooth, margin rounded, indented by the septa; spire depressed, involved; last volution slightly oblique, consisting of eight loculi; aperture contracted. The general form of this fossil is depressed, globular, with the involutions deviating slightly from the same plane. Not infrequently, however, the spire ascends in greater or less degree, and one of more loculi become visible beyond the single volution. Sometimes seven loculi only are visible in the volutions. The surface is smooth under the ordinary magnifier, and the outline is indented at the septa."

Listing found in Fauna of the Salem Limestone of Indiana section written by E.R. Cumings, J.W. Beede, E.B. Branson, and Essie A. Smith in the Indiana Department of Geology and Natural Resources Thirtieth Annual Report from 1905 on pages 1201-1202.

Thanks to Herb for the Salem Limestone sand.