The Effect of Taxonomic Corrections on Phanerozoic Generic Richness Trends in Marine Bivalves with a Discussion on the Clade’s Overall History

Abstract

This study uses a comprehensive, revised, and updated global bivalve dataset combining information from two major databases available to study temporal trends in Phanerozoic bivalve richness: the Sepkoski Compendium and the Paleobiology Database. This compilation results in greater taxonomic and stratigraphic coverage than possible with either of the two databases alone. However, there are challenges in directly comparing these two sources due to differences in their taxonomic designations and stratigraphic range information. Moreover, both of these datasets are fraught with a number of taxonomic errors, which can significantly bias the overall richness estimate. Additionally, a substantial number of taxonomic corrections were made before a new Phanerozoic bivalve richness curve was produced. The new generic taxonomic curve is comparable with the trajectory of the Sepkoski’s modern fauna and shows rapid and substantial diversification through the Ordovician, followed by a Paleozoic plateau, a Mesozoic high, and Cenozoic diversification after a small reduction in richness associated with the K/Pg extinction. The steep Cenozoic rise documented in the raw richness curve derived from the new dataset is likely real, and reflects the overall robustness and completeness of the bivalve fossil record.

The Miocene: The Future of the Past

“…Mollusks are the most species-rich group of marine animals and also have a very wide range of morphological diversity, life habits, and geographic and bathymetric distributions (Bouchet et al, 2016). Shell-bearing mollusks, especially bivalves and gastropods, which have left a rich fossil record, diversified through the Cenozoic, though this trend seems to have slowed during the Miocene compared to the Paleogene (Crampton et al, 2006;Mondal & Harries, 2016). During the Miocene, warm-water mollusks inhabited higher latitudes compared to both their Oligocene and present-day distribution (Beu & Maxwell, 1990;Kafanov & Volvenko, 1997;Nielsen & Glodny, 2009).…”

Were bivalves ecologically dominant over brachiopods in the late Paleozoic? A test using exceptionally preserved fossil assemblages

“…Bivalves and brachiopods have long provided a model system for testing methods and theories about biodiversity change, given their morphological and ecological similarities and their excellent fossil records (Gould and Calloway 1980; Foote and Sepkoski 1999; Valentine et al 2006; Payne et al 2014; Liow et al 2015). Though both clades first appeared in the early Cambrian (Williams and Carlson 2007; Parkhaev 2008), their relative diversity trajectories contrast strongly—globally, brachiopods were more diverse than bivalves in the Paleozoic and declined thereafter, whereas bivalves radiated steadily, becoming more diverse than brachiopods in the Mesozoic and Cenozoic (Miller and Sepkoski 1988; Sepkoski 1996; Bush et al 2016; Mondal and Harries 2016). Paleontologists and biologists have variously argued that bivalves were superior to brachiopods and competitively replaced them (Agassiz 1859; Mayr 1960; Steele-Petrovic 1979), that the shift in dominance was a contingent result of the Permian extinction (Gould and Calloway 1980), and that biotic interactions and mass extinction were both influential factors (Miller and Sepkoski 1988; Sepkoski 1996; Aberhan et al 2006).…”

Trophic and tectonic limits to the global increase of marine invertebrate diversity

“…We interpret this causal connection between plate kinematics and the diversity dynamics of marine invertebrates as a result of the positive relationship between seafloor age and number of geographical barriers to dispersal, which represents a major control on marine animal diversification 47 , 48 . Separate analyses on specific taxonomic groups (bivalves, gastropods, etc) might potentially unveil additional controls on diversity 49 , 50 .…”