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Heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars

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...

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Autores principales: Álvarez-Armada, Nidia, Cameron, Christopher B., Bauer, Jennifer E., Rahman, Imran A.
Formato: Online Artículo Texto
Lenguaje:English
Publicado: The Royal Society 2022
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9091856/
https://www.ncbi.nlm.nih.gov/pubmed/35538784
http://dx.doi.org/10.1098/rspb.2022.0258
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author Álvarez-Armada, Nidia
Cameron, Christopher B.
Bauer, Jennifer E.
Rahman, Imran A.
author_facet Álvarez-Armada, Nidia
Cameron, Christopher B.
Bauer, Jennifer E.
Rahman, Imran A.
author_sort Álvarez-Armada, Nidia
collection PubMed
description 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.
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spelling pubmed-90918562022-05-14 Heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars Álvarez-Armada, Nidia Cameron, Christopher B. Bauer, Jennifer E. Rahman, Imran A. Proc Biol Sci Palaeobiology 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. The Royal Society 2022-05-11 2022-05-11 /pmc/articles/PMC9091856/ /pubmed/35538784 http://dx.doi.org/10.1098/rspb.2022.0258 Text en © 2022 The Authors. https://creativecommons.org/licenses/by/4.0/Published by the Royal Society under the terms of the Creative Commons Attribution License http://creativecommons.org/licenses/by/4.0/ (https://creativecommons.org/licenses/by/4.0/) , which permits unrestricted use, provided the original author and source are credited.
spellingShingle Palaeobiology
Álvarez-Armada, Nidia
Cameron, Christopher B.
Bauer, Jennifer E.
Rahman, Imran A.
Heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars
title Heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars
title_full Heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars
title_fullStr Heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars
title_full_unstemmed Heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars
title_short Heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars
title_sort heterochrony and parallel evolution of echinoderm, hemichordate and cephalochordate internal bars
topic Palaeobiology
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9091856/
https://www.ncbi.nlm.nih.gov/pubmed/35538784
http://dx.doi.org/10.1098/rspb.2022.0258
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