J Syst Evol ›› 2020, Vol. 58 ›› Issue (6): 783-804.DOI: 10.1111/jse.12662

• Research Articles • Previous Articles     Next Articles

Better together: Joint consideration of anatomy and morphology illuminates the architecture and life history of the Carboniferous arborescent lycopsid Paralycopodites

William A. DiMichele1 and Richard M. Bateman2*   

  1. 1 Department of Paleobiology, NMNH, Smithsonian Institution, MRC‐121, Washington, DC 20560, USA
    2 Jodrell Laboratory, Royal Botanic Gardens Kew, Richmond, Surrey, TW9 3DS, UK
  • Received:2020-04-29 Accepted:2020-07-21 Online:2020-07-25 Published:2020-11-01

Abstract:

Paralycopodites Morey & Morey, a Carboniferous‐age arboreous lycopsid that grew in the tropical wetlands of Pangea, is the phylogenetically basalmost member of the Carboniferous stigmarian lycopsids to be conceptually reconstructed. We update its description through reciprocal illumination between anatomy (coal‐balls) and gross morphology (adpressions). Revised assessment of its architecture and development shows that the determinate, columnar main trunk eventually underwent several isotomous divisions to form a crown. Two opposite rows of closely‐spaced, compact lateral branches were initiated anisotomously throughout the trunk and crown, each branch further undergoing multiple anisotomous divisions to form an apparently planar scaffold for numerous bisporangiate cones. We infer that branches were initially emitted near‐vertically, but rapidly moved to a more horizontal position; they were abscised after the cones had matured but before the continuous phellogen had produced a centripetal periderm. Leaves were not abscised, though anatomy and morphology both suggest a photosynthetic economy that was localized within the plant body. Character content and clarity of interpretation make Paralycopodites the preferred name for the reconstructed plant rather than Anabathra, Ulodendron, or Bergeria. Phylogenetic analysis of rhizomorphic lycopsids based on a reduced spectrum of features observable in adpression returns the same topology as that based on a full matrix combining both anatomical and externally visible traits, permitting adpression fossils to be assigned to anatomically‐circumscribed genera rather than perpetuating an unnecessary parallel taxonomy.

The Carboniferous tree‐clubmoss Paralycopodites is conceptually reconstructed from disarticulated, anatomically‐preserved fossils in order to determine its phylogenetic position and to infer the developmental biology that dictated its remarkable architecture. Our biological and taxonomic conclusions can legitimately be expanded to encompass the more widespread compression mode of plant preservation.

Key words: adpression, anatomical preservation, Bergeria, Paleozoic, phylogeny, rhizomorphic lycophyte, Ulodendron