IS IT TIME TO QUIT?

Sampling is a critical issue in paleontological studies with many potential difficulties, including, among others, geographic sampling bias, incomplete sampling, taxonomic errors, stratigraphic errors and inconsistencies, rock quantity, sequence architecture, geographic distribution of rock, and various taphonomic considerations. Unfortunately, a predetermined statistically valid sampling scheme is rarely possible, and one is forced to collect all available data and then evaluate it post hoc to determine data suitability.

Anticosti Island, Quebec, offers a unique situation to study sampling among crinoids. Anticosti is a large, remote island that has experienced relatively limited collecting, the vast majority of all collected crinoids are present in museum collections, and Anticosti Island stratigraphy spans the end-Ordovician extinction event that had a profound affect on the macroevolutionary history of crinoids.

Standard rarefaction analysis is performed on these data. However, the unique aspects of Anticosti allow for comprehensive collection curves for Anticosti Island crinoids. Historically nine separate collections exist of Anticosti Island crinoids, four of which are from recent field seasons. These current investigations have increased the known crinoid species richness by 800 percent. So, can I stop collecting? Through evaluation of species richness, specimen abundance, time spent collecting in each formation, and stratigraphic thickness and area, one can conclude that the Ordovician-Silurian boundary crinoids from Anticosti Island have been well sampled.