Generally, my research draws upon fossil echinoderms, especially crinoids, as a medium for testing hypotheses of evolution and ecology. Adhering to a philosophy that "to understand fossils best one must know them in the rocks" (Crinoidea Flexibilia, Springer 1920), I dedicate much time to fieldwork. In particular, I make every effort to bolster my research with field data, paying careful attention to the sequence stratigraphic and environmental framework of fossil occurrences. Such experiences glean taphonomic and relative abundance data that are not often available in publications and museum collections. Moreover, I prefer specimen- and field-based strategies to data generation over literature-based approaches. I have great respect for literature-based science, but I prefer to press forward at the paleontological frontline, making fresh observations and generating original data.
Systematics is not my primary interest, but I am aware of the importance of addressing paleontological questions within a sound phylogenetic framework, thus I specialize in echinoderm taxonomy. Likewise, I embrace cladistic methodology in testing hypotheses of evolution and ecology. Although I've been accused of wearing "crinoid-colored glasses," crinoids are an exceptional group for analyzing spatiotemporal patterns of morphological and ecological diversity through time, especially the Paleozoic.
My research is centered in three areas. First are the evolutionary and ecological consequences of parasitism and predation on crinoids. Specifically, I study the interaction between crinoids and infesting snails called platyceratids. Despite the common view that the snails had no ill-effect on their crinoid hosts, I (with Tom Baumiller, University of Michigan) have demonstrated otherwise (e.g. snail-infested crinoids are significantly smaller than uninfested crinoids). Furthermore, we have presented data consistent with hypotheses that some crinoid characters evolved as a response to gastropod parasitism.
Predation on crinoids is another biotic interaction of interest. Crinoids, like all echinoderms, are able to regenerate lost body parts. Most regeneration in extant crinoids is a consequence of fish attacks, and the frequency of regenerating arms is positively correlated with predation intensity. Likewise, regenerated arms are observable in fossil crinoids; hence the fossil record of predation can be studied for this group. Most notably, this research demonstrates that during the Middle Devonian (~380 mya), a time referred to as the Middle Paleozoic Marine Revolution, patterns of crinoid arm regeneration are consistent with increases in shell-crushing predator diversity and the evolution of spines among crinoids. Such an "arms race" is predicted by the hypothesis of evolutionary escalation. This work has been published in Science and featured in national (and international) media. Currently, I am compiling additional regeneration data to test other predation-related hypotheses.
The second area of research involves early crinoid (and other echinoderm) morphological diversification and phylogeny. I've been tackling questions of crinoid plate homology that have long been a source of contention among echinoderm workers. One difficulty in resolving plate homology (and phylogeny) is that the early echinoderm fossil record is relatively poor. With hopes of filling this void, I have dedicated a considerable amount of time searching for Early Ordovician (~490 mya) echinoderms in the field. In the summer of 2004, perseverance was rewarded with an exceptional discovery in Idaho: A new (Tremadoc-Arenig) echinoderm fauna preserving more than two hundred specimens representing over 35 new echinoderm species and higher taxa. Not only does the fauna preserve the oldest known crinoids, but they are exquisitely preserved and buried in situ atop small algal mounds. Currently, I am preparing and describing this material (with Jim Sprinkle, University of Texas-Austin).
Lastly, I have a deeply-rooted (since the "Burlington Days") interest in Mississippian crinoid evolution and ecology. I'm particularly interested in the underlying causes of the rapid diversification of crinoids in the Early Mississippian (~350 mya) and the faunal turnover in the Late Mississippian that resulted in a restructuring of crinoid-clade dominance (and the rise of the Recent crinoid fauna). Broadly, I am working on several hypotheses related to the evolutionary ecology of Paleozoic echinoderms.