Morphometric data of the late middle Eocene to early Oligocene (~40 - 31 Ma) Coccolithophore Reticulofenestra (Order Isochrysidales)

The first size reduction (FSR) in the Reticulofenestra-Gephyrocapsa-Emiliania (RGE) lineage (Order Isochrysidales) which occurred in the early Oligocene (~ 32 Ma), is of great significance for understanding the lilliput effect that has affected the coccolithophore communities from late Eocene to this day. We conducted a morphologic analysis on the coccoliths of Reticulofenestra species that lived during the late middle Eocene to early Oligocene (~40-31 Ma), using marine sediments from the South Atlantic Ocean. Our data show increasing size and decreasing abundance of the large species during the late Eocene, leading to their disappearance at the FSR, and a concurrent decrease in the size variability of the small-medium-sized coccoliths whose diameter of the central opening had become very reduced. Although the cosmopolitan late Paleogene through Neogene size decrease in coccolithophores has been linked to the concomitant long-term decline in global pCO2, we suggest here that the FSR was..., Morphometric measurements were performed by randomly taking photographs in bright field of 10 to 15 fields of view per smear slide at 1000x magnification. A field of view typically contained 5 to 10 Reticulofenestra placoliths. For each sample, one hundred (100) specimens were measured. To avoid distortion caused by different orientations of the coccoliths as seen in light microscopy, only specimens horizontally oriented with the microscope stage were measured.Measurements were conducted manually using the biometric analysis software Fiji version 1.52 P by dragging ellipses over the contours of each placolith in order to measure its length and width. The long and short diameters of the central opening were likewise measured. Our procedure has resulted in a database of 6400 measurements for the whole study.We undertook a morphometric analysis with the double objective of quantifying the morphological features of the placoliths at any stratigraphic level and analyzing their change through..., This file includes the raw data and supplementary descriptions that required in the research. The supplementary material includes 1. coccolith assemblage, 2. data reproducibility evaluation, 3 estimated cell and coccosphere sizes that were mentioned in the manuscript and 4. our biostratigraphic interpretation.In the data file, we delineate coccolith morphology by two major structures, the distal shield and the central opening. Then the length and width of both are given in microns.One hundred specimens are measured in each sample, in which the sample IDs are present in the first specimens. The ages are estimated based on our biostratigraphic interpretation, which is introduced in the supplementary text.