Data from: The palaeobiological significance of clustering in acritarchs: a case study from the early Cambrian of North Greenland
Data files
Sep 05, 2024 version files 109 KB
Abstract
Aggregated clusters of acritarchs are relatively common among assemblages of organic-walled microfossils, yet such associations have received relatively little attention. Here we report a new diversity of acritarch clusters from the early Cambrian Buen Formation of North Greenland. The aggregation patterns of four genera (Skiagia, Comasphaeridium, Asteridium, and Synsphaeridium) are described together with their background population characteristics (presence of openings, inner bodies, and overall disparity) in order to better understand the palaeobiology of these acritarchs. The majority of Skiagia clusters were found to be monospecific despite significant intraspecific variability, a pattern that is suggestive of a strong environmental influence on Skiagia morphologies and aggregation habits. Abundant small (< 20 µm) Comasphaeridium vesicles were recovered in a broad range of chiefly monospecific clusters that have likely been formed under bloom conditions. A colonial habit is tentatively inferred from the tightly packed appearance of monogeneric Asteridium aggregates, and clearly evidenced by the highly conserved cellular structure of recovered Synsphaeridium clusters. A lack of excystment structures in Comasphaeridium and Asteridium vesicles suggests these taxa represent actively growing cells rather than resting cysts. Altogether, these findings shed new light on the diversity of cellular structures and lifestyles represented among Cambrian acritarchs, and illustrate a range of reproduction and defence strategies adopted by plankton in the face of novel environmental pressures.
README: Data from: The palaeobiological significance of clustering in acritarchs: a case study from the early Cambrian of North Greenland
https://doi.org/10.5061/dryad.t4b8gtj90
This tabular data consists of measurements and counts of acritarch specimens made on palynological slides forming the basis of the paper "The palaeobiological significance of clustering in acritarchs: a case study from the early Cambrian of North Greenland". Two additional files consist of correlation statistics obtained from the specimen counts of the acritarch taxon Skiagia. These values were calculated using the software package PAST.
Description of the data and file structure
Below is a list of file names with their associated descriptions.
"Synsphaeridium_list": list of recovered Synsphaeridium specimens and their characteristics. From left to right, coloumns refer to: the name of the photographed specimen; the arrangement of vesicles within the cluster; the number of vesicles within the cluster; additional remarks. Vesicles tend to be arranged radially, with a ring of N vesicles surrounding a central one (n). When this arrangement was observed, it was described as N+n. Cells marked n/a refer to missing data (the specimen wasn't photographed and the information available derives from notes taken during the analysis of slides). Abbreviations: ICI, intracellular inclusion.
"Skiagia_clusters_list": list of recovered Skiagia clusters and their characteristics. From left to right, coloumns refer to: the number of vesicles in the cluster; whether vesicles in the cluster are closed, opened or both (e.g., one vesicle closed and the other(s) opened); whether the cluster is monospecific, monogeneric or miscellaneous (i.e., consisting of multiple acritarch genera); species name of one of the clustered vesicle; species name of a second vesicle in the same cluster; species name of a third vesicle in the same cluster (if applicable); sample name where the cluster has been found; additional taxa present in the cluster (if any). Rows in grey feature a specimen of Skiagia sp. that could not be identified at species level. These clusters were later excluded from counts (see file named "Skiagia_clusters_counts"). Abbreviations: C, closed; O, opened; MS, monospecific; MG, monogeneric; Misc, miscellaneous.
"Skiagia_clusters_counts": Counts of monospecific, monogeneric and miscellaneous Skiagia clusters from all studied slides. The monospecificity rate is the number of monospecific clusters divided by the total number of clusters recovered, excluding Skiagia specimens that could not be identified at species level (i.e., Skiagia sp.). Abbreviations: N (MS), number of monospecific clusters; N (MG), number of monogeneric clusters; N (Misc), number of miscellaneous clusters (i.e., consisting of multiple acritarch genera); N (MG - Skiagia sp.), number of monogeneric clusters excluding those featuring Skiagia vesicles that could not be identified at species level; TOTAL - Skiagia sp., total number of Skiagia-bearing clusters minus clusters featuring a Skiagia specimen that could not be identified at species level.
"Cluster_counts_Skiagia_Comasphaeridium_Asteridium": Counts of Skiagia, Comasphaeridium and Asteridium vesicles in all 9 palynological slides studied. 200 specimens were counted per slide. Counts were performed on individual vesicles and clusters of various sizes, ranging from 2 to more than 20 specimens. Counts were made separately for each cluster size. The file contains 4 tabs corresponding to 3 different samples and the total counts (counts from 3 samples added up). Each tab consist of multiple tables corresponding to different slides, with the bottom coloured table corresponding to the total counts of the sample (counts from all slides of the same sample). At the bottom of this table, the percentage of clustered specimens is given, together with the percentage of clusters of less than 5 and 10 specimens.
"Asteridium_measurements": measurements of the length of processes and vesicle diameters in 16 specimens assigned to the acritarch taxon Asteridium. Both isolated and clustered specimens are included, and the number of vesicles per cluster is provided where applicable. Vesicles may appear ovoidal after flattening during slide preparation, hence minimum and maximum diameter values are provided. The breakage or bending of processes during palynological preparation occasionally results in uneven process lengths, hence minimum and maximum values are also provided for this parameter. Maximum values were retained for analysis and discussion in the paper. Cells marked n/a refer to missing data (the specimen wasn't photographed and the information available derives from notes taken during the analysis of slides). Symbols and abbreviations: SD, standard deviation; min, minimum; max, maximum; x̄, average value.
"Comasphaeridium_measurements": measurements of the length of processes and vesicle diameters in 35 specimens assigned to the acritarch taxon Comasphaeridium. Both isolated and clustered specimens are included, and the number of vesicles per cluster is provided where applicable. Vesicles may appear ovoidal after flattening during slide preparation, hence minimum and maximum diameter values are provided. The breakage or bending of processes during palynological preparation occasionally results in uneven process lengths, hence minimum and maximum values are also provided for this parameter. Maximum values were retained for analysis and discussion in the paper. Symbols and abbreviations: SD, standard deviation; min, minimum; max, maximum; x̄, average value.
"Skiagia_correlation": dataset input into PAST to calculate the linear regression depicted in Fig. 5 of the associated paper. From left to right, columns refer to: colour of data point (different for each species); symbol of data point; data point number (number of rows in PAST); relative abundance of the species in the slide; number of clusters featuring the species in the slide; name of the species; slide number.
"Skiagia_correlation_statistics": Spearman's coefficient rs and p-values of correlations between the relative abundance of Skiagia species and the number of clusters featuring them. Values were calculated using PAST on the basis of the entire dataset (i.e., file named "Skiagia_correlation_statistics") and data points from a single species, successively.
Code/Software
PAST 4 V. 1.0.0.0. was used for linear regressions and statistical tests.
Methods
Acritarchs were measured and counted based on palynological slides prepared by Vidal and Peel (1993). The material was collected by John S. Peel on 16th June 1974 and processed using a standard acid maceration procedure (Vidal 1988). Measurements were performed using the software ImageJ.
The statistical significance of correlations was calculated using Spearman’s rank-based correlation coefficient rs (Press et al. 1992), a non-parametric alternative to Pearson’s r. Rs and p values were obtained using the software package PAST (Hammer and Harper 2006).
- HAMMER, Ø. and HARPER, D. A. T. 2006. Paleontological data analysis. Blackwell, Oxford, 351 pp.
- PRESS, W. H., TEUKOLSKY, S. A., VETTERLING, W. T. and FLANNERY, B. P. 1992. Numerical recipes in C. Cambridge University Press, Cambridge, 994 pp.
- VIDAL, G. 1988. A palynological preparation method. Palynology, 12, 215–220.
- VIDAL, G. and PEEL, J. S. 1993. Acritarchs from the Lower Cambrian Buen Formation in North Greenland. Bulletin Grønlands Geologiske Undersøgelse, 164, 1–35.