The taxonomy, phylogeny, biostratigraphy, functional morphology, and paleoecology of Middle and Upper Ordovician (Blackriveran-Richmondian) Monoplacophora and bellerophontacean Gastropoda of the Cincinnati Arch region are discussed. Six genera and 29 species of monoplacophorans, and 13 genera and 56 species of bellerophontaceans are evaluated. The study is centered around new U.S. Geological Survey silicified collections.
A stratigraphic and paleontological analysis of 303 samples of Paleocene sediments of the eastern Gulf Coastal Plain of Mississippi, Alabama, and Georgia provided the basis for a geochronologic, quantitative paleoecologic, and paleoceanographic model.
The nature of taphonomic overprint affecting the fossil records of the regular echinoid Families Cidaridae, Diadematidae, Toxopneustidae and Echinometridae is investigated using a synthesis of actualistic and literature-derived data. The actualistic portion of this study focuses on the following extant members of the four families: Eucidaris tribuloides, Diadema antillarum, Tripneustes ventricosus and Echinometra lucunter. Population censuses of these animals in tropical reef and near-reef environments demonstrate that the distribution of macro- and microscopic skeletal material does not reflect the distribution of the living fauna. Field experiments with freshly-killed carcasses of Eucidaris, Diadema and Echinometra indicate that loss of all organic tissue occurs within six days after death, reducing these echinoids to essentially bleached carcasses.