Abstract
AbstractThe Ordovician–Silurian (~485–419 Ma) was a time of considerable evolutionary upheaval, encompassing both great evolutionary diversification and one of the first major mass extinctions. The Ordovician diversification coincided with global climatic cooling and paleocontinental collision, the ecological impacts of which were mediated by region-specific processes including substrate changes, biotic invasions, and tectonic movements. From the Sandbian–Katian (~453 Ma) onward, an extensive carbonate shelf developed in the eastern Baltic paleobasin in response to a tectonic shift to tropical latitudes and an increase in the abundance of calcareous macroorganisms. We quantify the contributions of environmental differentiation and temporal turnover to regional diversity through the Ordovician and Silurian, using brachiopod occurrences from the more shallow-water facies belts of the eastern Baltic paleobasin, an epicontinental sea on the Baltica paleocontinent. The results are consistent with carbonate shelf development as a driver of Ordovician regional diversification, both by enhancing broadscale differentiation between shallow- and deep-marine environments and by generating heterogeneous carbonate environments that allowed increasing numbers of brachiopod genera to coexist. However, temporal turnover also contributed significantly to apparent regional diversity, particularly in the Middle–Late Ordovician.
Highlights
The Ordovician and Silurian were intervals of tremendous evolutionary and environmental upheaval, encompassing both the great Ordovician biodiversification event (GOBE), and the onset and aftermath of the Late Ordovician mass extinction (LOME) (Webby et al 2004; Servais and Harper 2018; Rasmussen et al 2019; Stigall et al 2019)
Because the PBDB and SARV databases use different “collection” concepts, we assigned all occurrences to artificial collections, wherein a “collection” comprises all brachiopod occurrences within a lithostratigraphic unit at a single location, with location coordinates matched at a precision of three decimal places
Regional Richness over the Ordovician– Silurian.—The GOBE and LOME are expressed in the regional richness patterns derived from CR (Fig. 5)
Summary
The Ordovician and Silurian were intervals of tremendous evolutionary and environmental upheaval, encompassing both the great Ordovician biodiversification event (GOBE), and the onset and aftermath of the Late Ordovician mass extinction (LOME) (Webby et al 2004; Servais and Harper 2018; Rasmussen et al 2019; Stigall et al 2019). The GOBE had multiple global environmental drivers that were mediated by regional-scale processes, including carbonate platform development, biotic invasions, and latitudinal shifts due to tectonic movements (e.g., Kiessling et al 2003; Servais and Harper 2018; Stigall 2018). The impact of these regional processes on diversity is exemplified by the eastern Baltic paleobasin.
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