DOI: 10.5061/dryad.zs7h44jjn
title: Data from: Sustained shift in the morphology of organic-walled microfossils over the Ediacaran-Cambrian transition

description: The early (~1650 – 540 mya) history of eukaryotes was punctuated by
 several major – but enigmatic – environmental perturbations that
 potentially influenced the evolution of the Proterozoic biosphere, and the
 changing structure of Earth systems leading up to the Cambrian Explosion
 of animals. Reconstructing the manner in which eukaryotes responded to
 these events represents an innovative lens with which to understand what
 these perturbations actually represent, as well as the links between
 geosphere and biosphere during a critical period in eukaryotic evolution.
 In this study, we analyze organic-walled microfossil size and morphology
 across the Ediacaran-Cambrian transition. We illustrate that the decrease
 in vesicle diameter –previously shown to occur across the
 Ediacaran-Cambrian transition – began in the Ediacaran following the
 ‘Shuram’ carbon isotope excursion. This size decrease was accompanied by
 an increase in relative process length across the Ediacaran-Cambrian
 transition, which has not been previously quantified. Finally, following
 the ‘Shuram’ excursion, we illustrate a sustained shift in overall
 morphology. This shift in morphology may have been driven by nutrient
 stress enhanced by environmental change and/or the increased importance of
 planktonic lifestyles, highlighting the expansion of microbial eukaryotes
 into the plankton as a key step in the establishment of modern marine food
 webs.
description: # Data from: Sustained shift in the morphology of organic-walled
 microfossils over the Ediacaran-Cambrian transition Dataset DOI:
 [10.5061/dryad.zs7h44jjn](10.5061/dryad.zs7h44jjn) ## Description of the
 data and file structure This dataset was compiled from morphological data
 from 33 publications that included systematic descriptions of
 Ediacaran-Cambrian acritarch assemblages. Vesicle size, process length,
 and host lithology were recorded and taxa were scored for two continuous
 characters and 23 presence/absence characters largely focused on process
 morphology. We used R to create boxplots for acritarch size and visualize
 acritarch morphospace with nonmetric multidimensional scaling. We ran
 sensitivity tests using various subsampling analyses. Empty cells reflect
 values not applicable or published (such as process length or number of
 specimens reported, see below).  ### Files and variables #### File:
 NMDS\_code.R **Description:** This is code used to create and analyze the
 morphospace in this manuscript with NMDS. #### File:
 FigS5\_subsampling\_code.R **Description:** This is code used to run
 subsampling analyses of acritarch size data.  #### File: Boxplots\_code.R
 **Description:** This is code used to create the boxplots in this
 manuscript and gather statistical data on acritarch size. #### File:
 Acritarch\_data.csv **Description:** This is the dataset used in this
 manuscript. See Supplementary Figure 1 for illustration of morphological
 characters.  ##### Variables * * Genus: Genus name * Species: Species name
 * Age: Age bins, BSE (Before and including the ‘Shuram’ excursion [635–567
 Ma]), PSE (Post the ‘Shuram’ excursion [566–539 Ma]), and EC (early
 Cambrian [538–509]). * Formation: Formation name * Lithology: Host
 lithology category - siliciclastics, carbonate, chert and phosphorites *
 VD: average vesicle diameter (µm) (if cell is empty, then a diameter was
 not reported) * PL : average process length (µm) (if cell is empty, then
 there are no processes or a length was not reported) * PL_VD: ratio of
 average process length to average process diameter (if cell is empty, then
 there are no processes or a length was not reported) * Num: number of
 specimens reported by author in publication (if cell is empty, then number
 of specimens was not reported) * Vesicle_size: 1=&lt;100 µm, 2=100-200µm,
 3=&gt;200µm * Process_length: 0=absent, 1= &lt;10%, 2=10-40%, 3= &gt;40% *
 The following variables are scored for presence (1) or absence (0) except
 for reference: * Process_irregular: irregularly arranged processes *
 Process_dense: densely arranged processes * Process_branching: distally
 branching processes * Process_hollow: hollow processes *
 Process_cylindrical: cylindrical shaped processes * Process_bulbous:
 bulbous shaped processes * Process_hooked: distally hooked processes *
 Process_conical: conical shaped processes * Process_domed: domed shaped
 processes * Process_heteromorphic: heteromorphic processes *
 Process_expandedbase: processes with exbanded base * Process_thin:
 processes &lt;1 µm * Process_blunt: blunt tipped processes *
 Process_pointed: pointed tipped processes * Process_rounded: rounded
 tipped processes * Process_funnel: funnel tipped processes * Process_CWVI:
 processes are open (communicate with) to vesicle interior * OuterWall:
 processes are within outer wall * Flange: equatorial flange *
 Surface_ornamentation: surface ornamentation  * Colonial or aggregate:
 colonial or aggregate form * Vesicle: presence of vesicle * Ref: Reference
 of publication * Median_age: Median or plotting age (Ma, millions of
 years) assigned to formation based on available age constraints (see
 FormationAges.xlsx) #### File: FormationAges.xlsx **Description:** This is
 a list of available age constraints for the formations in this analysis.  
 ##### ## Code/software All analyses were performed using the statistical
 computing software R, v. 4.3.1. Three scripts are included that create
 boxplots, perform NMDS analysis and perform subsampling analyses.  ##
 Access information Data on microfossil size, morphology and formation age
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 species of small acritarch with a porous wall structure from the early
 Cambrian of Estonia and implications for the fossil record of eukaryotic
 picoplankton. Palynology. 40(3):343-56. | |
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