Epidermal morphology and ecological significance of Glossopteris pubescens nom. nov. from the Brazilian Permian (Sakmarian)

• Redescription of a glossopterid species based on cuticular analysis
• Cuticular analysis has been performed in over 100 leaves from a single locality.
• The lower epidermis features elaborate hair cover.
• Trichomes and papillae could have multiple functions under wet-dry oscillations.
• Environmental cyclicity is inferred to have influenced epidermal plasticity.

A Brazilian glossopterid species is reassigned and redescribed based on cuticular analysis. The original name (Guerra-Sommer, 1992) is illegitimate because it is a later homonym of Glossopteris papillosa Srivastava (1969). Thus, the new name Glossopteris pubescens is erected as a replacement for G. papillosa Guerra-Sommer. The leaf adpressions come from a tonstein layer within a Sakmarian coal seam (U/Pb age 291 ± 1.3 Ma) of the Faxinal Coalfield, southern Paraná Basin, Brazil (Rio Bonito Formation). Leaf fragments macerated in Schulze's solution yielded larger cuticle fragments than those previously described, totaling over 100 analyzed leaves. The unique ornamentation of the lower side of the lamina comprises simple trichomes and trichome base complexes densely concentrated on the venation system. These epidermal structures are interpreted under the light of new paleoecological data for the Faxinal Coalfield which include humidity oscillations, wildfire occurrences and influence of volcanic activity. These paleoenvironmental factors are suggested to have played a main role in the development of the xeromorphic cuticle structures which possibly had a multitask function during both dry and wet cycles, mainly as protection of stomata against excessive humidity and air dust.