10.5061/DRYAD.NZS7H44RP
Álvarez Armada, Nidia
0000-0001-8299-6355
University of Bristol
Cameron, Christopher
University of Montreal
Bauer, Jennifer
University of Michigan–Ann Arbor
Rahman, Imran
0000-0001-6598-6534
Natural History Museum
Scan files, 3D reconstructions, data spreadsheet and supplementary files
for Heterochrony and parallel evolution of echinoderm, hemichordate and
cephalochordate internal bars
Dryad
dataset
2021
FOS: Natural sciences
deuterostomes
Stylophora
pharyngeal openings
gill bars
Respiratory structures
homology
Palaeontological Association
https://ror.org/05v5yjs39
PA-CD202101
2022-06-16T00:00:00Z
2022-06-16T00:00:00Z
en
https://doi.org/10.1098/rspb.2022.0258
https://doi.org/10.5281/zenodo.4945559
https://doi.org/10.5281/zenodo.4945563
16955394218 bytes
8
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Deuterostomes comprise three phyla with radically different body plans.
Phylogenetic bracketing of the living deuterostome clades suggests the
latest common ancestor of echinoderms, hemichordates and chordates was a
bilaterally symmetrical worm with pharyngeal openings, with these
characters lost in echinoderms. Early fossil echinoderms with pharyngeal
openings have been described, but their interpretation is highly
controversial. Here, we critically evaluate the evidence for pharyngeal
structures (gill bars) in the extinct stylophoran echinoderms Lagynocystis
pyramidalis and Jaekelocarpus oklahomensis using virtual models based on
high-resolution X-ray tomography scans of three-dimensionally preserved
fossil specimens. Multivariate analyses of the size, spacing and
arrangement of the internal bars in these fossils indicate they are
substantially more similar to gill bars in modern enteropneust
hemichordates and cephalochordates than to other internal bar-like
structures in fossil blastozoan echinoderms. The close similarity between
the internal bars of the stylophorans L. pyramidalis and J.
oklahomensis and the gill bars of extant chordates and hemichordates is
strong evidence for their homology. Differences between these internal
bars and bar-like elements of the respiratory systems in blastozoans
suggest these structures might have arisen through parallel evolution
across deuterostomes, perhaps underpinned by a common developmental
genetic mechanism.
X- ray tomography Specimens were imaged with X-ray micro-tomography
and synchrotron tomography. Details of scan settings are provided in
Supplementary Table 1. Raw files can be found under the specimen's
name. Three-dimensional reconstructions Tomographic datasets for
the specimens were digitally reconstructed using the SPIERS software
suite. See electronic supplementary information and Supplementary Figure 1
for details. Measurements of length were standardised against the total
length of the pharynx or internal thecal cavity for each model, whereas
measurements of width, depth and spacing were standardised against the
diameter of the pharynx or internal thecal cavity. Finalised versions of
the reconstructions in .spv and .spvf files can be found under the
specimen's name. Data analysis Raw dataset can be found on
internal_bar_data.csv. Standardised measurements of the structures of
interest were analysed quantitatively in R 3.6.3 using principal component
analysis (PCA) and linear discriminant analysis (LDA). The analyses were
conducted using the stats (v3.6.3) and MASS (v7.3.51.5) packages. LDA
results were further interrogated via partition plots for every
combination of two variables using the klaR (v0.6.15) package. In
addition, the normalised data were analysed using MANOVA, ANOVA at 95%
confidence and post-hoc testing (Holm-Bonferroni and Tukey 95% confidence
tests) using the stats (v3.6.3) package. Further methodological details
and R scripts are provided as electronic supplementary information.
- raw data scan file I- reconstruction .spv file. This is a finalised
version of the reconstruction with possibility of alteration. II-
reconstruction .spvf file. This is a finalised version of the
reconstruction without possibility of alteration, older versions of
SPIERSview might not be able to process it. III- measurement acquisition
(reconstruction file + final.csv). For instructions see supplementary
files (electronic_material.pdf). IV- multivariate analysis (final.csv +
final_rcode.R). All raw scan files have the scan info and settings
included in the uploaded folder except Jaekelocarpus oklahomensis where
the settings can be found at the original data
source http://digimorph.org/specimens/Jaeckelocarpus_oklahomensis/