georgia-science.com

This Late Eocene echinoid is from the Tivola Limestone of Houston County, Georgia, near the community of Clinchfield. Similar ones are found in the Ocala Limestone of Florida and related limestone units.

The Eocene Epoch was a time of global warmth and great biodiversity, especially among echinoids (sand dollars, sea urchins, heart urchins). The Middle and Late Eocene of the Coastal Plain of Mississippi, Florida, Alabama, Georgia, North Carolina, and South Carolina have produced a rich diversity of echinoid genera and species.

These are among my favorite types of fossils. There are three other species of this sand dollar found in Georgia, one older, the other two younger. This genus became extinct at the end of the Eocene Epoch, approximately 37 million years ago.

Here are some links for the Periarchus genus: Periarchus pileussinensis, and Periarchus lyelli.

Here is a slide series concerning the Sandersville Limestone, where the echinoid Periarchus quinquefarius is found.

Here is some more Tertiary echinoid info.