DIVERSITY AND RELATIVE ABUNDANCE OF A PALEOCOMMUNITY OF CRINOIDS (ECHINODERMATA) FROM A WALDRON SHALE (HOMERIAN, WENLOCK) LAGERSTÄTTE

The Middle Silurian (Homerian, Wenlock) Waldron Shale of south-central Indiana, Shelby County contains an abundance of exquisitely preserved fossils, including a diverse assemblage of crinoids. The crinoids of the Waldron Shale were initially described by James Hall (1882). Because of the exceptional preservation of the Waldron biota, the Waldron Shale is well suited for paleoecological study (Peters and Bork, 1999).

Relatively few studies have attempted to reconstruct the paleoecology of the Waldron Shale. Previous authors used species-abundance models to infer changes in the paleoecological communities. Peters and Bork (1999) sampled multiple localities in south-central Indiana and analyzed species abundance for all identifiable macrofossil fauna encountered, including several crinoid genera.

This study is based on crinoid specimens from a single locality that were collected over a span of many years. Some rare species that are represented by only a few specimens are included. This study estimates the true diversity and relative abundance of the crinoids within each of the various paleoecological communities (sensu Peters and Bork, 1999) that are represented at the locality.