A New Reconstruction of the Iridopteridalean Ibyka amphikoma Skog et Banks from the Middle Devonian of Gilboa, New York State

Abstract

Premise of the ResearchClarifying the basic anatomy and morphology of Devonian fossils is essential for understanding the origin and radiation of land plants in deep time. Iridopteridales is a major Devonian plant group for which there is no presently established whole plant concept.  MethodologyThe type material of the iridopteridalean Ibyka amphikoma Skog et Banks was reprepared and redescribed to clarify the details of branching patterns, and enable comparison with the previously described anatomy.  Pivotal ResultsAt least three orders of branching are known. Insertions of laterals is dominantly whorled, sometimes imperfectly, with distinct internodes. Within a whorl, branches may substitute for dichotomous appendages, with the latter more numerous. A new reconstruction is presented. Based on the partially preserved anatomy, and on the basis of comparison with anatomically preserved Iridopteridales, we infer that traces to the branches and appendages are emitted one from each arm of a multi-ribbed actinostele. This pattern contrasts with the only other iridopteridalen preserved both anatomically and morphologically, Compsocradus laevigatus Berry et Stein, in which traces are emitted from alternate ribs in each whorl, with angular offset between adjacent whorls.  ConclusionsThis basic understanding of the essentially whorled organisation in Iridopteridales, as well as the overall morphology and anatomy, will benefit attempts to infer the broader phylogeny of early land plants, including the origins of horsetails and ferns.

Rooting Portions of a Young Pseudosporochnalean from the Catskill Delta Complex of New York

“…Camera lucida drawings and high-resolution stitched images are deposited along with the specimen (comprising both impression and permineralized preparations) at the New York State Museum, Albany, NY (NYSM 19,312). More detailed versions of these figures, plus images of each section surface, may also be found online (Stein et al 2022). Stein, Berry, Hernick & Mannolini 2023 -12…”

“…The focus of this report is the order Pseudosporochnales (Berry and Stein 2000, Durieux et al 2021, Berry et al 2022 among the earliest plants in the fossil record to attain large size in what seems to have been an explosive phase in plant evolution (Stein et al 2012, Berry 2019.…”