REVISITING THE BIVALVE AND BRACHIOPOD SAGA USING NEW TOOLS AND DATA: THEY REALLY DID NOT PASS EACH OTHER IN THE NIGHT

The classic story of clade-clade interaction between brachiopods and bivalves was shown to be poorly supported by Gould and Calloway in their seminal paper in 1980 (Paleobiology 6:383-396). Subsequent authors in various publications, including Miller, Sepkoski, Payne and others, in part revived the idea that brachiopods really are evolutionarily inferior to bivalves. However, the question whether bivalves causally drove brachiopods to extinction remains unanswered. Here, we use the latest data from the Paleobiology Database to estimate diversification dynamics of both brachiopod and bivalve genera over the Phanerozoic while simultaneously estimating sampling probability, such that diversification estimates are not confounded by temporal sampling heterogeneity. We then apply a time series approach using Stochastic Differential Equations (SDEs) that circumvents many statistical issues in commonly used regression and time series techniques to model causal links between brachiopod and bivalve diversification time series and five paleoenvironmental proxies over the same time period. We found that the five paleoenvironmental proxies, including oxygen and carbon isotopes and eustatic sea levels, had no statistical relationships to the time series of brachiopod and bivalve extinctions and originations. In contrast, we inferred robust relationships among bivalve and brachiopod time series, leading us to conclude that high bivalve extinction rates causally and positively drove brachiopod origination rates, i.e. brachiopods were allowed comebacks when bivalves were (temporarily) in the decline.