A reassessment of the taxonomy of Oligocarpia bellii (Late Pennsylvanian, Sydney Coalfield, Nova Scotia, Canada)

Abstract

Restudy of the types of Oligocarpia bellii ZODROW & MCCANDLISH provides new taxonomic insight, based on combined data from first-time study of cuticles, and studies of reproductive organs with in-situ spores. The thin oligocarpian cuticle is composed of irregularly-shaped, polygonal epidermal cells in the intercostal field (10-40 mu m in diameter) that have deeply undulating anticlinal walls on both the adaxial and abaxial surfaces, and slightly larger polygonal cells with moderately undulating anticlinal walls in the costal field. Long (10-35 mu m) and short (3-8 mu m) papillae are common adaxially, but less so abaxially. Both surfaces show uniseriate multicellular trichomes (50 mu m), and bases. The hypostomatic pinnule has cyclocytic stomata (20-26 mu m long, and 13-21 mu m wide) radially surrounded by 6-8 curvilinearly, or polygonally-shaped subsidiary cells (9-16 mu m long, and 5-7 mu m wide); stomata and subsidiary cells are sunken into the epidermis. Stalked sporangia are biseriate with oblique, thick-walled annuli (cells 40-120 mu m long and 15-25 mu m wide), crossed by a stomium that forms the line of dehiscence. Labrate, subtriangular-circular in-situ spores show simple laesurae, are thin-walled, microgranulate, 19 (25) 31 mu m in diameter; and correlate to the dispersed spore genus Granulatisporites (IBRAHIM) POTONIE et KREMP. Epidermal and stomatal characteristics of O. bellii do not compare with extant marattialean ferns. In-situ Granulatisporites palynology is of little help in this respect, as there are several similar types from different parent plants which makes correlation impossible. Features of the reproductive organs of O. bellii are similar to those seen in the Family Sermayaceae EGGERT et DELEVORYAS which we regard ancestral to Gleicheniaceae.