Rodlets from Compressed Medullosalean Plant Fossils: Chemical and Morphological Studies (Late Pennsylvanian Sydney Coalfield, Canada)

Fragmented compression specimens of medullosalean fronds have been voluminously described over the past 200 years. However, the literature on rodlets is scarce. We addressed the questions (i) of common occurrence in these fronds, (ii) what made the fronds so strong to bear such a biomassive load, and (iii) what is the chemical make up of rodlets that expressed as striae and ridges (medullosalean hallmark) occur on these fronds? Recovered were soluble and insoluble, black, round and flat, opaque or translucent rodlets that are up to 5 mm long and ca. 10-111 μm wide, and are typed as (i) transparent, (ii) insoluble, or (iii) soluble in Schulze’s solution. In situ insoluble rodlets can be distinguished from associate coal and cuticle-free compression foliage and rachides by relatively high aromaticity and low aliphatics, although their chemical composition is unknown. Rodlets are presumably related to sclerenchymatous tissue in support of strength/stability of these sizeable medullosalean fronds.