{"title":"Symmetry in graptolite zooids and tubaria (Pterobranchia, Hemichordata)","authors":"Jörg Maletz","doi":"10.1111/ede.12394","DOIUrl":null,"url":null,"abstract":"<p>Extant and fossil pterobranchs show distinct symmetry conditions of the individual zooids and their tubaria that are not necessarily comparable. The strict bilateral symmetry in the zooids of extant Cephalodiscida is modified to a considerable anatomical asymmetry in extant Rhabdopleurida. This type of left–right asymmetry can be recognized as antisymmetry, as dextral and sinistral developments are equally common. Antisymmetry is also recognized in the rhabdopleurid tubaria and in the proximal development and branching of planktic graptoloids. The antisymmetry of the graptoloid tubarium is modified during the Tremadocian time interval to a fixed or directional asymmetry. From the latest Tremadocian or earliest Floian onwards, proximal development in the Graptoloidea is invariably dextral and very few examples of a sinistral development have been found. The transition from antisymmetry to directional asymmetry can only be recognized in the graptolite tubaria, as the anatomy of the zooids is unknown from the fossil record. Directional asymmetry is not recognized in extant Pterobranchia.</p>","PeriodicalId":12083,"journal":{"name":"Evolution & Development","volume":"23 6","pages":"513-523"},"PeriodicalIF":2.6000,"publicationDate":"2021-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/ede.12394","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Evolution & Development","FirstCategoryId":"99","ListUrlMain":"https://onlinelibrary.wiley.com/doi/10.1111/ede.12394","RegionNum":3,"RegionCategory":"生物学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"DEVELOPMENTAL BIOLOGY","Score":null,"Total":0}
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Abstract
Extant and fossil pterobranchs show distinct symmetry conditions of the individual zooids and their tubaria that are not necessarily comparable. The strict bilateral symmetry in the zooids of extant Cephalodiscida is modified to a considerable anatomical asymmetry in extant Rhabdopleurida. This type of left–right asymmetry can be recognized as antisymmetry, as dextral and sinistral developments are equally common. Antisymmetry is also recognized in the rhabdopleurid tubaria and in the proximal development and branching of planktic graptoloids. The antisymmetry of the graptoloid tubarium is modified during the Tremadocian time interval to a fixed or directional asymmetry. From the latest Tremadocian or earliest Floian onwards, proximal development in the Graptoloidea is invariably dextral and very few examples of a sinistral development have been found. The transition from antisymmetry to directional asymmetry can only be recognized in the graptolite tubaria, as the anatomy of the zooids is unknown from the fossil record. Directional asymmetry is not recognized in extant Pterobranchia.
期刊介绍：
Evolution & Development serves as a voice for the rapidly growing research community at the interface of evolutionary and developmental biology. The exciting re-integration of these two fields, after almost a century''s separation, holds much promise as the focus of a broader synthesis of biological thought. Evolution & Development publishes works that address the evolution/development interface from a diversity of angles. The journal welcomes papers from paleontologists, population biologists, developmental biologists, and molecular biologists, but also encourages submissions from professionals in other fields where relevant research is being carried out, from mathematics to the history and philosophy of science.
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