Ups and downs of belemnite diversity in the Early Jurassic of Western Tethys

Although belemnites form a major clade of extinct cephalopods, the early stage of their diversification remains poorly known in time and space. Here we investigate the first diversification episodes of belemnites (order Belemnitida) using a new species-level database encompassing the Hettangian-Aalenian interval (Early Jurassic-earliest Middle Jurassic) and covering the Western Tethys. Rarefied richness shows a four-fold increase from the Planorbis chronozone to the Ibex chronozone, a strong decrease between the Margaritatus and Spinatum chronozones, followed by a drop in the Spinatum-Serpentinum interval that is coeval with the second-order Toarcian biological crisis. The Bifrons chronozone records a high richness that departs significantly from those of the surrounding chronozones. A last richness peak in the Dispansum chronozone precedes a decrease towards the Aalenian. Biogeographic analyses do not reveal any clear large-scale provincialism for belemnites, in sharp contrast with amm..., The database of the present work is constructed upon a near-exhaustive, species-level taxonomic revision of the available literature, covering 150 years of palaeontological investigations (1867-2018): 64 publications (Appendix S1) were selected according to the criteria described hereafter and analysed. Some publications are monographs dealing with a large palaeogeographic area, whereas others are more geographically restricted. Only rarely were data from the authors’ own samples or from museum collections added (Appendix S2). Because published data are far from being homogeneous, we constructed a dataset respecting several strict criteria. Data from the literature have been evaluated only if they contained specimen illustrations (drawings and/or photographs) in order to check the original species attribution. Occurrences that were simply cited were ignored. Once this first criterion was validated, geographical and stratigraphic information were checked. In cases where one of these two ..., , # Data from: Ups and downs of belemnite diversity in the Early Jurassic of Western Tethys

Dataset DOI: [https://doi.org/10.5061/dryad.tqjq2bvx2](https://doi.org/10.5061/dryad.tqjq2bvx2)

## Description of the data and file structure

The database of the present work is constructed upon a near-exhaustive, species-level taxonomic revision of the available literature, covering 150 years of palaeontological investigations (1867–2018): 64 publications (Neige et al. 2020, Appendix_S1_Biblio.rtf) were selected according to the criteria described here-after and analysed. Some publications are monographs dealing with a large palaeogeographical area (e.g. Doyle1990, 1992), whereas others are more geographically restricted (e.g. Schumann 1974). Only rarely were data from the authors’ own samples or from museum collections added (Neige et al. 2020, appendix S2). Because published data are far from being homogeneous, we constructed a dataset respecting several strict criteria. Data from the literat...,