Tectonic and eustatic controls on the palaeobiogeographic distribution of Eocene bivalves.

This article focuses on the global palaeobiogeography of Eocene bivalve genera and how their distribution patterns were influenced by major tectonic, climatic, and sea-level changes during the Eocene epoch (56–34 million years ago). Using comprehensive data from the Paleobiology Database and additional sources, the study identifies formal palaeobiogeographic provinces for each Eocene stage and analyzes their evolving relationships through cluster and network analyses. Key findings include increased bivalve diversity and provincial expansion during the early Eocene warming (Paleocene–Eocene boundary) and diversity decline with provincial contraction during the late Eocene cooling (Eocene–Oligocene boundary). The study highlights faunal connections facilitated by ocean currents such as the North Atlantic Gyre, Northern Equatorial Current, Alaska and Oyashio currents, and the role of tectonic events like the closure of the Tethys Sea and the disappearance of the Western Interior Seaway in shaping provincial affinities and migration routes. Imparidentia and Pteriomorphia bivalves predominantly defined these provinces, with protobranchs playing a significant role in high-latitude provinces.