Abstract Detail

Paleobotany

Berry, Christopher [1], Stein, William [2], Wyatt, Amy [3].

Untangling Ibyka: Morphology of Devonian Iridopteridales from Laurussia and western Gondwana.

Ibyka amphikoma Skog et Banks from the Givetian of Gilboa, NY, was presented, based on compression fossils with limited preserved anatomy, as an upright plant with a ribbed protostele typical of Iridopteridales, yet with helical insertion of appendages and lateral branches rather than whorled as has been established for most anatomically preserved forms. A clear whorled morphology was demonstrated in compressions of Anapaulia Berry et Edwards from Venezuela, prompting restudy of Ibyka by Berry, Cordi and Stein. Ibyka was then shown to have predominantly whorled branching in the larger orders of axes, and combined with anatomical evidence it was noted that in iridopteridaleans like Ibyka, it would be expected that at each of the whorls, separated by clear internodes, one trace, to a dichotomous appendage or a single lateral branch, would be emitted from each rib of the stele. Berry and Stein described a new genus, Compsocradus, from the late Givetian of Venezuela in which traces were emitted from every other rib, with the alternate ribs involved in trace production at successive whorls. Berry then studied the type material of Hyenia vogtii Høeg from the Frasnian of Svalbard, which appeared to have the same basic architecture as Ibyka amphikoma, and was transferred to Ibkya. This prompted restudy of the type species of Hyenia, H. sphenophylloides Nathorst from the Givetian of Norway. Although the compressions are poorly preserved, and characteristic recurved appendage tips are absent, H. sphenophylloides has alternating whorls of appendages as described for Compsocradus. Therefore morphologically preserved members of Givetian/Frasnian Iridopteridales from Laurussia and western Gondwana so far appear to come in two distinct types – spiny forms with superposed whorls and spineless forms with alternating whorls.

1 - Cardiff University, Earth And Environmental Sciences, Main Building, Park Place, Cardiff, SGM, CF10 3AT, United Kingdom
2 - Department Of Biological Sciences, Dept Of Biological Sciences, Suny - Binghamton, Binghamton, NY, 13902, United States
3 - Cardiff University, Earth and Environmental Sciences, Main Building, Park Place, Cardiff, Wales, CF10 3AT, UK

Keywords:
Devonian
Fossil
morphology.

Presentation Type: Oral Paper
Session: PL4, Paleobotany: Honoring Fran Hueber - Session II
Location: /
Date: Tuesday, July 20th, 2021
Time: 1:45 PM(EDT)
Number: PL4006
Abstract ID:751
Candidate for Awards:None