The genus Aberlemnia and its Silurian–Devonian fossil record

Abstract

The genus Aberlemnia from the Early Devonian of Scotland is revised herein, based on its type-material A. caledonica. Emended diagnoses are provided. A. caledonica shows simple isotomously branched axes in the way the basal-most segments are the longest, and each segment further distally is shorter. Terminal axial segments form subtending axes, each bearing a single sporangium. The sporangium is circular, oval, rarely reniform in front view, vase-shaped in sagittal view, consisting of two equal valves with the line of dehiscence reaching the basal part of the sporangium. A new species Aberlemnia krizii sp. nov is described from the Pridoli, Silurian of the Barrandian Area, Czechia, in Central Europe. It is similar to A. caledonica in habitus, isotomous branching and isovalvate sporangia. It differs in having shorter subtending axes, sporangia of clearly reniform shape and markedly broader than high, an absence of radial striation of sporangia, and the line of dehiscence reaching as far as 1/3 of the way down the sporangium. The difference is also in size: A. caledonica is more robust. Aberlemnia is positioned on a clade line leading to the Lycophytina.