Zooid size reduction in cyclostome bryozoans from the Late Triassic to the present-day

Body size evolution is a focus of palaeobiological interest, but few studies have examined long-term changes in the size of the modular zooids of colonial animals. Here we investigate changes in zooid size from the Late Triassic to the present-day among encrusting cyclostome bryozoans of a common morphotype attributed informally to ‘Berenicea’. We begin with the naïve hypothesis that cyclostome bryozoans should demonstrate size evolution similar to cheilostome bryozoans, which have maintained a constant mean zooid size. Unexpectedly, a striking pattern of decreasing zooid size through time was found in ’Berenicea’. We then hypothesized that decreasing levels of oxygen could make smaller zooid sizes more optimal because of their greater surface area/volume, i.e., cyclostome zooid size might be tracking a changing adaptive landscape over 200 million years. Despite some evidence for a statistical correlation between ‘Berenicea' zooid size and oxygen, there is no hint of any causal rel..., Cyclostome form genus fossil 'Berenicea' were collected over different field expeditions. They were cleaned and processed then scanning electron micrographs (SEMs) were taken of these specimens. The images of these specimens were then manually measured. The SEMs are supplied with this dataset, as are the measurements of the specimens from the SEMs.
, , # Data from: Zooid size reduction in cyclostome bryozoans from the Late Triassic to the present-day

[https://doi.org/10.5061/dryad.x95x69pvt](https://doi.org/10.5061/dryad.x95x69pvt)

## Description of the data and file structure

The SEM images provided in Berenicea SEM jpgs zip folder are the bases for the measurements given in the excel file 'Berenicea' zooid width data.xlsx

## Files and variables

### Folder: Berenicea_SEM_jpgs.zip

**Description:** 

Scanning electron micrographs of Berenicea. The individual file names correspond to the first column (SEM number) in the Excel file 'Berenicea' zooid width data.xlsx

The metadata for each image is available in the column \"Metadata\" of the Excel file 'Berenicea' zooid width data.xlsx

### Folder: Code_and_Data.zip

#### File: 'Berenicea' zooid width data.xlsx

This is the main data file for the analyses. The following describes the columns in Sheet 1

* SEM number: corresponds to the file names in Berenicea_SEM_jpgs.zip
* stage: geol...,