The presence of ligule in southern South America neopaleozoic lycopsids: the case of Bumbudendron versiforme

COTUREL, ELIANA P.; GUTIÉRREZ, PEDRO R.

Bahía

Conferencia; XIV International Palynological Congress and X International Organisation of Palaeobotany Conference; 2016

Lycopodiopsids are the oldest vascular plants living actually, they appeared in the Silurian and had their major diversity in the Carboniferous. Those were the times were the Isoetalean clade diversified and became cosmopolitan; Lepidodendron Sternberg dominated Euramerican coal swamps, while smaller lycopsids lived in the Angara and Gondwana lands. The leaf cushion helps to characterize and differentiate vegetative remains of lepidodendrids. Gondwanan and Angaran lycopodiopsids differs from Euramerican by the presence of an infrafoliar bladder instead of parichnos; Angaran and Euramerican bear ligule pits; absent in some of the South American lycopodiopsids. Ligule is a small structure located dorsally to the microphyll. For taxa historically known as eligulated (Lepidodendropsis Lutz), a considerable variation in the morphology of the leaf cushions and both ligule and ligule pit were detected dependent on the preservation of the stem. This motivates the revision of other eligulated taxa to clarify about the presence or absence of ligule. Bumbudendron Archangelsky, Azcuy et Wagner comprises South American lycopodiopsids with small cushions in lepidodendroid phyllotaxis, infrafoliar bladder and without ligule pit. Bumbudendron versiforme Gutiérrez, Césari et Limarino from Agua Colorada Formation (La Rioja) is characterized by fusiform leaf cushions with a variable length-width ratio in a single stem. The presence of ligule pit was suggested in stems assigned to this species from the Loma Larga and Solca Formations (Pennsylvannian). Similar ligulated remains were reported from the Melo Formation (Lower Permian of Uruguay). They belong to a small stem, possibly a branch end, and the leaf scars are similar to those of B. versiforme. The type material of B. versiforme were re-investigated and a structure assignable to ligule pit was recorded. It is suggestive that B. versiforme species should be removed from Bumbudendron. Tomiodendron Radczenko is the closest genus, which in some species shows fusiform cushions, infrafoliar bladder and ligule pit. These species are known from the Lower Carboniferous of Angara (T. kemeroviense Radczenko), and from the late Visean warm temperate beds of Paracas (T. peruvianum Pfefferkorn et Alleman, Ambo Formation, Perú). Tomiodendron sp. was reported from Loma de Los Piojos Formation (Córdoba, Argentina), referred to the FNC Biozone from Argentina. The dispersal of the tomiodendrids from Angara to Gondwana during the Carboniferous was recently proposed. The presence of ligulated ?B.? versiforme in the Upper Carboniferous of Argentina suggests that, after the retreat of the warm temperate Paracas? belt, tomiodendrids could have remained until Permian in South America.