Reproductive organs and in situ spores of Asteroxylon mackiei Kidston & Lang, the most complex plant from the lower devonian Rhynie chert

Kerp H, Wellman CH, Krings M, Kearney P, Hass H

Zusammenfassung

Asteroxylon mackiei is the largest and most complex vascular land plant from the Lower Devonian RhynieChert. Fertile remains were first reported nearly 40 years after the description of the sterile axes but were notdescribed in greater detail. In this contribution, we document several fertile axes from longitudinal andtransverse thin sections. Sporangia, consisting of two kidney-shaped valves, are interspersed among thenonvascularized leaflike appendages and attached to the axis with a short pedicel. The sporangia are curvedand lie close to the axis. Sporangia possess a dome-shaped central structure that forms the continuation of theshort stalk into the sporangial cavity. The in situ spores are identified as Retusotriletes cf. triangulatus. Thesporangia were apparently abscised after sporulation. Fertile zones with leaflike appendages and sporangiaalternate with sterile zones with only leaflike appendages within an axis, suggesting a periodicity of growth.

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