I am an invertebrate paleontologist specializing in Paleozoic-age echinoderms, especially from the Cambrian, Ordovician, and Mississippian Periods. I have worked on many groups of primitive echinoderms, including members of the extinct Subphylum Blastozoa (proposed in 1973), early crinoids, extinct edrioasteroids, stylophorans, and ctenocystoids (co-named in 1969). I am primarily interested in the systematics, phylogeny, and paleoecology of these fossil echinoderms. I have done recent field work to collect fossil echinoderms in the central and southern Rocky Mountains, especially Utah and Nevada, but have previously collected fossil echinoderms in Oklahoma, west Texas, Missouri, and the southern and central Appalachians. I have published or edited three monographs or books and about 40 research papers and book chapters since 1967.