{"title":"Characterizing and distinguishing the earliest woody euphyllophytes based on secondary xylem anatomy: method development and application.","authors":"Emma Casselman, Alexandru M F Tomescu","doi":"10.1093/aob/mcaf122","DOIUrl":null,"url":null,"abstract":"<p><strong>Background and aims: </strong>The oldest vascular cambial growth (woody growth) has been recognized in several Early Devonian (ca. 410-395 Ma) euphyllophytes. Incomplete preservation of these fossils, in multiple cases, makes it difficult to evaluate their taxonomic diversity, in the absence of quantitative methods for distinguishing plants based on secondary xylem anatomy. In turn, this hinders understanding of their implications for the evolution of plant development. To develop and apply metrics that quantify secondary xylem anatomy and allow for conclusive comparisons, we investigated extant and Early Devonian fossil woody taxa.</p><p><strong>Methods: </strong>We developed multiple metrics for quantifying tracheid size as a function of position in the secondary xylem and tested them against a dataset of extant gymnosperm wood. The four metrics that showed consistent trends within taxa and captured differences among taxa were then applied to previously recognized Early Devonian fossil woody taxa and to previously undescribed Early Devonian woody specimens to compare them and evaluate taxonomic diversity and placement of the new fossils.</p><p><strong>Key results: </strong>The four new secondary xylem metrics, considered alongside other anatomical characters, differentiated the previously recognized Early Devonian taxa from each other, allowed assignment of two of the new fossils to the previously described species Franhueberia gerriennei and separated two new woody euphyllophyte taxa.</p><p><strong>Conclusions: </strong>The metrics developed here for quantifying secondary xylem anatomy are effective in demonstrating conspecificity and in separating distinct woody taxa, especially in combination with data on the primary xylem and xylem rays. They provide a new method for assessing the taxonomic placement of fossils with incomplete preservation, opening up a new avenue for exploring fossil plant diversity and for characterizing anatomy, with implications for the evolution of plant development.</p>","PeriodicalId":8023,"journal":{"name":"Annals of botany","volume":" ","pages":""},"PeriodicalIF":3.6000,"publicationDate":"2025-06-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Annals of botany","FirstCategoryId":"99","ListUrlMain":"https://doi.org/10.1093/aob/mcaf122","RegionNum":2,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"PLANT SCIENCES","Score":null,"Total":0}
引用次数: 0
Abstract
Background and aims: The oldest vascular cambial growth (woody growth) has been recognized in several Early Devonian (ca. 410-395 Ma) euphyllophytes. Incomplete preservation of these fossils, in multiple cases, makes it difficult to evaluate their taxonomic diversity, in the absence of quantitative methods for distinguishing plants based on secondary xylem anatomy. In turn, this hinders understanding of their implications for the evolution of plant development. To develop and apply metrics that quantify secondary xylem anatomy and allow for conclusive comparisons, we investigated extant and Early Devonian fossil woody taxa.
Methods: We developed multiple metrics for quantifying tracheid size as a function of position in the secondary xylem and tested them against a dataset of extant gymnosperm wood. The four metrics that showed consistent trends within taxa and captured differences among taxa were then applied to previously recognized Early Devonian fossil woody taxa and to previously undescribed Early Devonian woody specimens to compare them and evaluate taxonomic diversity and placement of the new fossils.
Key results: The four new secondary xylem metrics, considered alongside other anatomical characters, differentiated the previously recognized Early Devonian taxa from each other, allowed assignment of two of the new fossils to the previously described species Franhueberia gerriennei and separated two new woody euphyllophyte taxa.
Conclusions: The metrics developed here for quantifying secondary xylem anatomy are effective in demonstrating conspecificity and in separating distinct woody taxa, especially in combination with data on the primary xylem and xylem rays. They provide a new method for assessing the taxonomic placement of fossils with incomplete preservation, opening up a new avenue for exploring fossil plant diversity and for characterizing anatomy, with implications for the evolution of plant development.
期刊介绍：
Annals of Botany is an international plant science journal publishing novel and rigorous research in all areas of plant science. It is published monthly in both electronic and printed forms with at least two extra issues each year that focus on a particular theme in plant biology. The Journal is managed by the Annals of Botany Company, a not-for-profit educational charity established to promote plant science worldwide.
The Journal publishes original research papers, invited and submitted review articles, ''Research in Context'' expanding on original work, ''Botanical Briefings'' as short overviews of important topics, and ''Viewpoints'' giving opinions. All papers in each issue are summarized briefly in Content Snapshots , there are topical news items in the Plant Cuttings section and Book Reviews . A rigorous review process ensures that readers are exposed to genuine and novel advances across a wide spectrum of botanical knowledge. All papers aim to advance knowledge and make a difference to our understanding of plant science.
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