# Record of Foraminifera test composition throughout the Phanerozoic

## TL;DR

This paper examines how foraminifera shell composition changed over 541 million years, finding that ocean chemistry changes had limited long-term impact on their diversity.

## Contribution

The study provides a comprehensive analysis of foraminiferal wall-type diversity and extinction rates across the Phanerozoic Eon.

## Key findings

- Calcareous foraminifera maintained around 77% proportional diversity during the Cenozoic Era.
- Calcareous wall-type extinction rates declined during the Mesozoic and Cenozoic Eras.
- Only two mass extinction events significantly reduced calcareous wall-type diversity.

## Abstract

Marine calcifiers produce calcareous structures (e.g. shells, skeletons or tests) and are therefore sensitive to ocean chemistry. Nevertheless, the long-term evolutionary consequences of marine carbonate changes are not well understood. This article compares calcareous and non-calcareous responses to ocean chemistry changes throughout the Phanerozoic Eon (541 million years ago to present). To accomplish this, we calculated proportional wall-type diversity, origination rates and extinction rates for 2282 benthic foraminiferal genera. Calcareous origination and extinction rates fluctuated throughout the Palaeozoic Era (541–251.9 million years ago), but during the Mesozoic Era (251.9–66 million years ago), calcareous origination and extinction rates stabilized following the evolution of pelagic calcifiers. Despite variations in Cenozoic Era (66–0 million years ago) foraminifera diversity, calcareous wall types maintained around 77% proportional diversity. Although calcareous wall-type extinction rates decline during the Mesozoic and Cenozoic, Phanerozoic foraminifera wall-type changes during individual events are largely contingent upon contemporaneous conditions rather than overarching trends. Of the Big Five mass extinction events, calcareous wall-type proportions only decreased at the end-Permian (73% to 26% diversity) and end-Triassic (56% to 50% diversity). These results suggest long-term ocean chemistry changes were not the main driver of foraminiferal wall-type diversity through time.