ESTIMATING ABSOLUTE DIVERSITY: HOW MANY DINOSAUR GENERA WERE THERE?

Approximately 500 valid genera of non-avian dinosaurs have been described, almost half since 1990, yet many genera undoubtedly remain to be discovered. How many genera were there altogether? We demonstrate a statistical method for estimating the total number of non-avian dinosaur genera, including those that have not yet been found. Much of the previous work on estimating total diversity, often in the ecology literature, uses capture-recapture methods. However, such methods are not applicable in paleontology. Here we apply a statistical method of Zhang and Stern (2004) for estimating total diversity that accounts for the incompleteness of the fossil record. We use a Bayesian Dirichlet-Multinomial model and Markov Chain Monte Carlo simulation to calculate point estimates and interval estimates for total diversity. Note that this work differs from attempts to estimate total diversity using sampling standardization (e.g., for Phanerozoic marine genera) because we adjust for undiscovered genera rather than for unequal sampling, and we estimate the absolute number of genera over the entire Mesozoic rather than relative counts at different points in time.