TAPHONOMY OF EOCENE OPHIUROIDS FROM THE COASTAL PLAIN OF GEORGIA

Ophiuroids are known from the Late Ordovician to the recent. There are approximately 1400 living species of ophiuroids. In comparison there are 18 known species from the Cretaceous. There have been only 14 species of ophiuroids described from the Tertiary with 5 from the Eocene. The Eocene ophiuroid species have been described from Belgium, England, Venezuela, the Antarctic Peninsula, and New Jersey, where this species was described from disarticulated specimens.

Most ophiuroid species described in the fossil record consist of whole to nearly complete, articulated specimens. Very few fossil ophiuroid species have been described from disarticulated specimens. The most identifiable parts of an ophiuroid are the outer arm plates and the internal vertebral ossicles.

Well-preserved disarticulated ophiuroid specimens composed of outer arm plates and internal vertebral ossicles have been found to be abundant in the Sandersville Limestone member of the Tobacco Road Sandstone and the Cooper Marl from the coastal plain of Georgia. The ophiuroid specimens appear to all be from a single species of ophiuroid tentatively placed in the genus Ophiomusium. Relative abundance of ophiuroid parts is about 250 parts per kilogram of limestone sample. Comparing this abundance with sediment from a saltwater tank with captive ophiuroids indicates that the Eocene ophiuroid assemblage is most likely a death assemblage not from loss of arms in life. The abundance of ophiuroids in the fossil record is most likely skewed due to identification biases of workers only identifying articulated specimens.