Late Ordovician Paleontology, Sedimentology
and Stratigraphy in Ohio, Indiana and Kentucky
A Keck Geology Consortium Project
June 19 - July 16, 1999
Rugose corals (Order Rugosa) are a well documented fossil group that can be found in many marine deposits in the Paleozoic. The organism consisted of a polyp that lived in a calcareous shell. The shell of solitary rugosans is conical with vertical partitions known as septa. Being soft in form, the polyp (tentacled soft body) of the coral is not preserved; all that remains is the corallum or the shell (Boardman et al., 1987). It is assumed that the rugose coral situated itself into an appropriate position on the substrate in its earlier polyp stage (before it secreted its protective shell). The trend with larval organisms is that they do not survive in areas long enough to grow unless they make it to their appropriate environment. While many questions concerning this organism have been answered, the life position the solitary rugosans favored on the sea floor is still debated. In my project I will work on this question. I am concentrating on solitary rugose corals (Grewingkia canadensis) in the Whitewater Formations in the Cincinnatian Group (Upper Ordovician) in Indiana.
The presence of encrusting bryozoans and borings on the corallum will shed
light on the life position of the coral, because parts exposed during the
life of the coral will have more encrustations and borings even if the
individual became exposed after the death of the coral. In the study
conducted by Elias et al. (1990), it was suggested that the organism was
oriented as upright as possible. These researchers suggested that the
shapes of the shell were caused by high energy currents during its
development. That study mentioned that bryozoans were present on the
corallum which suggests that these areas were possibly exposed. In
addition, they state that initial colonization may have occurred while the
hosts were living. If I were to measure and compare the bryzoans and
borings on the corallum, then I could find a relationship between the life
position and the coral exposed. Areas where the shell was exposed were
colonized by the moss- like bryozoan, and by borers. Thus, I expect to
find that there are more bryozoans and borings on the parts exposed in life
position than on the parts exposed after the death of the polyp.
