DOI: 10.5061/dryad.9ghx3ffvp
title: Diversity of organic-walled microfossils in the phosphates of the ca. 1 Ga Diabaig Formation, Torridon Group, NW Scotland

description: Precambrian organic-walled microfossils preserved in fine-grained
 sedimentary rocks constitute the earliest fossil record of eukaryotic
 life. The Mesoproterozoic-Neoproterozoic transition coincided with major
 innovations in the evolution of early eukaryotes, including the radiation
 of crown-group lineages, represented in these rocks by candidate red
 algae, green algae, and fungi. However, the diversity of these early
 eukaryotes is yet to be fully explored. Here, we present a systematic
 description of the microfossil assemblage preserved in exceptional detail
 within sedimentary phosphatic nodules and bands in the Diabaig Formation
 of the ca. 1 Ga Torridon Group of northwest Scotland. Recent work has
 highlighted the lacustrine or estuarine nature of its depositional
 environment and confirmed that these fossils may include the oldest known
 non-marine eukaryotes. We identify 11 morphotaxa from new collected
 material, including the new species Minimarmilla multicatenaria gen. et
 sp. nov, two undoubted eukaryotes, and two probable eukaryotes. The latter
 include Pterospermopsimorpha sp., and a new network-forming unnamed taxon.
 These microfossils present an important window on eukaryotic
 diversification in non-marine aquatic environments during the
 Mesoproterozoic–Neoproterozoic.
description: # Diversity of organic-walled microfossils in the phosphates of the ca. 1
 Ga Diabaig Formation, Torridon Group, NW Scotland Dataset DOI:
 [10.5061/dryad.9ghx3ffvp](10.5061/dryad.9ghx3ffvp) ## **Description of the
 data and file structure** "SupData_1_SHERPA_datasets_(v.2).xls"
 has 14 sheets with the data used for SHERPA software analysis of the cell
 shape of multiple *Eosynechococcus* spp. and *Eohalothece lacustrina*
 specimens from different studies, including ours. The first sheet contains
 the final comparison of counted and analysed fossil cells, which was used
 to create the Supplementary Information Figure 2. The second sheet has the
 information of each dataset analysed with SHERPA software. The rest of the
 sheets have the individual results obtained after each SHERPA analysis
 performed on a given dataset. Each dataset is labelled by study name as
 shown in the second sheet.
 "SupData_2_Fossil_assemblages_and_Eohalothece_(v.2).xls"
 contains 3 sheets with fossil taxa data from different assemblages and
 length vs width comparisons of *Eosynechococcus* spp. and *Eohalothece
 lacustrina* cells. The first sheet shows organic-walled microfossils from
 10 Meso-Neoproterozoic assemblages and their biological affinity
 classification (prokaryotes, eukaryotes, or unknown) using
 "=COUNTIF(range, criteria)". These fossils and references are in
 Supplementary Information Table 2. The second sheet contains a bar chart
 of the classification data obtained in sheet 1 and used for Figure 2. The
 third sheet has length vs width comparisons and preliminary plots used to
 create Figure 6. ## **Files and variables** ### 1)    File:
 SupData\_1\_SHERPA\_datasets\_(v.2).xls **Sheet 1:** "Final
 comparison_SI Fig 2" **Description:** Summary sheet comparing cell
 shape classifications across all studies (31 columns) **Variables and
 descriptions:** * **Cell shape/Study**: Study identifier for row data *
 **Cylindrical**: Count of cells classified as cylindrical shape *
 **Ellipsoidal**: Count of cells classified as ellipsoidal shape *
 **Cylindrical + tapered**: Count of cells with cylindrical base and
 tapered ends * **Ellipsoidal + tapered**: Count of cells with ellipsoidal
 base and tapered ends * **Tapered**: Count of cells classified as purely
 tapered shape * **Total cells counted**: Total number of cells analysed
 per study * **Cell shape %/Study**: Percentage breakdown section header *
 **Cylindrical** (repeated): Percentage of cylindrical cells *
 **Ellipsoidal** (repeated): Percentage of ellipsoidal cells *
 **Cylindrical + tapered** (repeated): Percentage of cylindrical + tapered
 cells * **Ellipsoidal + tapered** (repeated): Percentage of ellipsoidal +
 tapered cells * **Tapered** (repeated): Percentage of tapered cells Note:
 The repeated columns correspond to multiple analysis groups in the
 comparison sheet. These groups are: 1. **Section 1** (Columns 1-7): Raw
 counts. So, "Cell shape/Study" + 5 shape categories + total 2.
 **Section 2** (Columns 10-15): Percentages. So, "Cell shape
 %/Study" + 5 shape categories (see corresponding bar chart) 3.
 **Section 3** (Columns 22-27): Set of counts for *Eohalothece lacustrina*
 (see corresponding chart pie) 4. **Section 4** (Columns 31-36): Set of
 counts for *Eosynechococcus moorei* (see corresponding chart pie) 5.
 **Section 5** (Columns 40-45): Set of counts for *Eosynechococcus spp.*
 (see corresponding chart pie) Each section repeats the same 5 cell shape
 categories (Cylindrical, Ellipsoidal, Cylindrical + tapered, Ellipsoidal +
 tapered, Tapered) but for different subsets of the 11 studies. **Sheet
 2:** "Datasets information" **Description:** Metadata about each
 study dataset (7 columns) **Variables and descriptions:** * **Study**:
 Reference to the published study/author * **Name given**: Internal dataset
 name or identifier * **Assemblage**: Fossil assemblage or formation name *
 **Paleoenvironment**: Ancient environmental setting (marine, lacustrine,
 etc.) * **Age**: Geological age of the samples * **Material**: Type of
 material analysed (e.g., rock, sediment) * **Cell number**: Total number
 of cells/specimens in dataset   **Sheet 3:** "Templates for
 SHERPA" **Description:** Template shape data used by SHERPA software
 for classification (12 columns) **Variables and descriptions:** *
 **File**: Template image filename * **Folder**: Directory location of
 template * **Area / µm²**: Template area in square micrometers *
 **Perimeter / µm**: Template perimeter in micrometers * **Width / µm**:
 Template width in micrometers * **Height / µm**: Template height in
 micrometers * **Width/Height Ratio**: Aspect ratio of template shape *
 **Smoothness**: Contour smoothness measure (estimates outline roughness) *
 **CDF**: Convexity Defection Factor (percentage difference between shape
 and convex hull) * **PCAF**: Percent Concave Area Fraction (compares areas
 of contour and convex hull) * **CHMDF**: Convex Hull Maximum Distance
 Factor (measures convexity defects) * **Template is convex**: Boolean
 indicating if template shape is convex **Sheets 4-14:** Individual Study
 Results **Description:** Detailed SHERPA analysis results for individual
 studies (40-41 columns each) **Variables and descriptions:** **1.     
 Basic Object Properties:** * **File**: Source image filename * **Folder**:
 Directory path of source image * **Area**: Object area in square
 micrometers * **Perimeter**: Object perimeter in micrometers * **Width**:
 Object width along major axis in micrometers * **Height**: Object height
 along minor axis in micrometers * **Costae**: Distance between costae
 (experimental feature, not recommended for routine use) **2.      SHERPA
 Processing Parameters:** * **Segmentation Method**: Algorithm used to
 separate object from background (Otsu, RATS, Canny, etc.) *
 **Optimization**: Morphological operators applied to repair segmentation
 faults (Opening, Closing, etc.) * **Template**: Best matching template
 filename * **Best**: Best template match identifier * **Hu Match**: Hu
 invariant matching score between object and template * **Standard
 Deviation**: Standard deviation of intensity within inner 50% of object
 area * **Width/Height Ratio**: Aspect ratio of detected object **3.     
 Shape Quality Indicators:** * **Contour**: Contour quality measure *
 **Form Factor**: Heuristic descriptor (4π × Area / Perimeter²) *
 **Quality**: Overall quality assessment * **Template Match**: Template
 matching quality score * **Rectangularity**: How rectangular the shape is
 * **Compactness**: Shape compactness measure (Perimeter² / (4π × Area)) *
 **Ellipticity**: How elliptical the shape is * **Triangularity**: How
 triangular the shape is * **Roundness**: How round/circular the shape is
 **4.      Convexity Measures:** * **Convexity** (two columns): Different
 convexity measurements * **CDF**: Convexity Defection Factor (absolute
 measure) * **PCAF**: Percent Concave Area Fraction (absolute measure) *
 **CHMDF**: Convex Hull Maximum Distance Factor (absolute measure) *
 **CDF** (second instance): CDF comparison with template * **PCAF** (second
 instance): PCAF comparison with template * **Compactness** (second
 instance): Compactness comparison with template * **Convexity** (second
 instance): Convexity comparison with template **5.      Analysis
 Results:** * **Ranking**: Overall ranking index (lower = better quality) *
 **Export**: Boolean flag for data export selection **6.      Cell Shape
 Classification Results:** * **Cylindrical (Cyl final.jpg)**:
 Classification as cylindrical cell type * **Cylindrical + tapered (Cyltap
 final.jpg)**: Classification as cylindrical with tapered ends *
 **Ellipsoidal (El final.jpg)**: Classification as ellipsoidal cell type *
 **Ellipsoidal + tapered (Eltap final.jpg)**: Classification as ellipsoidal
 with tapered ends * **Tapered (Tap final.jpg)**: Classification as purely
 tapered cell type * **Total cells**: Total count for this analysis
 **7.      Study-Specific Sheet Names:** 1. Strotther&Wellman_Torridon
 2. Strotther&Wellman_Nonesuch 3. Hofmann 4. Golubic&Campbell 5.
 Tang et al 6. Miao et al 7. Shukla et al 8. Rodriguez et al_Torridon 9.
 Loron et al 10. Knoll et al 11. Rodriguez et al_Draken **Notes for DRYAD
 Data Dictionary:** * µm = micrometers * CDF, PCAF, CHMDF are morphological
 analysis parameters from SHERPA software * Cell shape categories are the
 main classification outputs * Some column headers contain line breaks
 (shown as \n) in the original data   ### 2) File:
 SupData\_2\_Fossil\_assemblages\_and\_Eohalothece\_(v.2).xls **Sheet 1:**
 "Fossil count for Fig 2" **Description:** Compendium of
 organic-walled microfossils across 10 Meso-Neoproterozoic assemblages with
 biological affinity classification (12 columns). Legend: Prokaryote (X),
 Eukaryote (Y), Unknown (Z) **Variables and descriptions:** *
 **Assemblages**: Row identifier/fossil taxon names * **Torridon Group
 Scotland**: Fossil counts from Torridon Group assemblage, Scotland *
 **Lower Shaler Supergroup Canada**: Fossil counts from Lower Shaler
 Supergroup, Canada * **Mbuji-Mayi Supergroup Democratic Republic of
 Congo**: Fossil counts from Mbuji-Mayi Supergroup, DRC * **Atar/El Mreïti
 Group Mauritania**: Fossil counts from Atar/El Mreïti Group, Mauritania *
 **Lower Madhubani Group India**: Fossil counts from Lower Madhubani Group,
 India * **Bylot Supergroup Canada**: Fossil counts from Bylot Supergroup,
 Canada * **Lakhanda Group Russia**: Fossil counts from Lakhanda Group,
 Russia * **Liulaobei Formation China**: Fossil counts from Liulaobei
 Formation, China * **Gouhou Formation China**: Fossil counts from Gouhou
 Formation, China * **Mirojedikha Formation Russia**: Fossil counts from
 Mirojedikha Formation, Russia * **Organic-walled microfossils**: Summary
 category or total counts **Sheet 2:** "Final Bar Chart_Fig 2"
 **Description:** Bar chart data comparing biological affinity
 classifications across assemblages (11 columns) **Variables and
 descriptions:** * **Assemblage**: Geological formation/group identifier *
 **Lower Shaler Sg**: Classification data for Lower Shaler Supergroup *
 **Liulaobei Fm**: Classification data for Liulaobei Formation * **Atar/El
 Mreïti Gp**: Classification data for Atar/El Mreïti Group * **Lower
 Madhubani Gp**: Classification data for Lower Madhubani Group *
 **Mbuji-Mayi Sg**: Classification data for Mbuji-Mayi Supergroup * **Lower
 Bylot Sg**: Classification data for Lower Bylot Supergroup * **Lakhanda
 Gp**: Classification data for Lakhanda Group * **Mirojedikha Fm**:
 Classification data for Mirojedikha Formation * **Torridon Gp**:
 Classification data for Torridon Group * **Gouhou Fm**: Classification
 data for Gouhou Formation **Sheet 3:** "Eosyne comparison_Fig 6"
 **Description:** Cell length vs width comparison data for
 *Eosynechococcus* and *Eohalothece* taxa (25 columns) **Variables and
 descriptions:** **Section 1:** General species data (Columns 1-9) *
 **Species name**: Taxonomic name of the species * **Length**: Cell length
 measurements in micrometers * **Width**: Cell width measurements in
 micrometers * **Average (μm)**: Average dimensions in micrometers *
 **Average l/w ratio**: Average length to width ratio * **No. of measured
 specimens**: Number of specimens measured for each species * **Reference
 number**: Numerical reference identifier * **Reference**: Literature
 citation/source reference **Section 2:** Comparative analysis data
 (Columns 11-15) * **Species name** (repeated): Species identifier for
 comparison section * **Length** (repeated): Length data for comparative
 analysis * **Width** (repeated): Width data for comparative analysis *
 **Number**: Specimen count or identifier number * **Aspect ratio l/w**:
 Length to width aspect ratio **Section 3:** *Eohalothece lacustrina*
 comparative data (Columns 23-25) * ***E. lacustrina*** (Nonesuch): Data
 for *E. lacustrina* from Nonesuch Formation * ***E. lacustrina***
 (Torridon): Data for *E. lacustrina* from Torridon Group * ***E.
 lacustrina*** (This study): Data for *E. lacustrina* from current study
 **Notes for DRYAD Data Dictionary:** * Sg = Supergroup, Gp = Group, Fm =
 Formation (geological unit abbreviations) * μm = micrometers * l/w =
 length to width ratio * Biological affinity classifications likely include
 prokaryotes, eukaryotes, unknown * Data processed using Excel COUNTIF
 function for taxonomic counting * References correspond to Supplementary
 Information Table 2 ## **Code and software** No code used, only SHERPA
 software. ## **Access information** Other publicly accessible locations of
 the data: Contact the authors at any time.