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

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