Spores of the Rhynie chert plant Aglaophyton (Rhynia) major (Kidston and Lang) D.S. Edwards, 1986

Detailed studies have been undertaken on in situ spores of the Rhynie chert plant Aglaophyton (Rhynia) major (Kidston and Lang) D.S. Edwards. The in situ spores exhibit a variety of preservational types that are described. In several specimens, spores are exceptionally preserved: some apparently preserve an outer, enveloping, callose wall and others preserve the plasma membrane and possibly also cell contents. The in situ spores are relatively simple trilete spores with retusoid structure that are entirely laevigate and have a distinctive thinning associated with the trilete mark. They may be accommodated in the dispersed spore genus Retusotriletes. Identical spores occur dispersed in litter/soil horizons preserved in the chert (as individual spores, including germinating spores, in spore masses and in coprolites), and are also a common element of dispersed spore assemblages from throughout the stratigraphical sequence of the Rhynie outlier. The dispersed forms are placed with Retusotriletes sp. CW-A, as described by Wellman [Wellman, 2004. Palaeoecology and palaeophytogeography of the Rhynie chert plants: evidence from integrated analysis of in situ and dispersed spores. Proc. R. Soc. London, Ser. B 271, 985–992; Wellman, in press. Spore assemblages from the “Lower Old Red Sandstone” deposits of the Rhynie Outlier, Scotland. Trans. R. Soc. Edinburgh: Earth Sci.], and it is concluded that the dispersed spore taxon Retusotriletes sp. CW-A was produced by A. major. Integrated evidence from dispersed and in situ spores (particularly those exceptionally preserved) permits a detailed reconsideration of the many lines of evidence pertaining to the reproductive biology and ecology of the plant A. major.