Taxonomy of Early Mississippian gulate megaspore assemblage from northern Bolivia

A taxonomic study of gulate megaspores, characterised by having an apical prominence associated with the trilete mark, from the Toregua Formation, Retama Group, Early Carboniferous (mid-upper Tournaisian) of northern Bolivia was performed. To achieve this, the general morphology and wall structure of around a hundred of specimens of megaspores isolated from palynologic residues of the Pando X-1 and Manuripi X-1 boreholes were studied in detail and thoroughly described and illustrated using light, fluorescence and scanning electron microscopy. From this analysis, nine morphospecies of the genus Lagenicula were identified, including a new species (L. morbelliae sp. nov.), of which some were considered Mississippian in age (L. brasiliensis, L. microechinata, cf. L. crassiaculeata, cf. L. hirsutoida) and others (L. devonica, L. illizii, L.magna, L. media) were interpreted as likely reworked forms from Devonian deposits. The sporoderm morphological features of the studied megaspores confirm the botanical affinity assigned to heterosporous arborescent lycopsids (Lepidocarpaceae/Lepidodendraceae), which would have formed dense forests, not only of great dimensions and variability but also with ecological complexity, during the Early Carboniferous in Bolivia. •Ultrastructural studies of spore broaden knowledge about botanical affinity.•Spores of extant and fossil lycopsids have a similar ultrastructure.•Lycopsids spores wall formation would have persisted relatively unchanged over time.