Devonian plants - Haplostigma Seward - of Argentina ana Bolivia: new records, palynoassemblages, and ages

DI PASQUO, M.M.; NOETINGER, S.; STARCK, D.; GRADER, G.; ISAACSON, P.; MOREL, E.

Gramado

Congreso; XXIII Congresso Brasileiro de Paleontologia; 2013

Sociedade Brasileira de Paleontologia

The present contribution refers to new records of Haplostigma Seward from southern Bolivia (two localities) and northern Argentina (two localities). The Argentinean material, collected from the Pescado Formation at the Angosto del Pescado and Los Monos Formation at Balapuca (by D.S. in 2000), comprises fragmented stems as compressions and impressions; one of which shows a bifurcation (1.2 cm in width, 8 cm in length) and spiny lateral appendices. In southern Bolivia, fragmented and oxidized impressions and one cast of Haplostigma stems were recovered from the Iquiri Formation (collected by MdP in 2007) at Yesera Centro and Dique. The specimens are associated to scarce small brachiopods (Rhipidomiella sp.). Scarce and poorly preserved stems were obtained from the Los Monos Formation at Mataral (by MdP in 2007). All the specimens are quite similar being characterized by imprints of sub-herbaceous stems (1-1.3 cm in width, up to 8 cm in length) with surfaces covered by helically disposed scars with a strong vertical arrangement (8-9 rows, phyllotaxis angle up to 36°) and with an oval ?longitudinal to circular shape; vascular traces are likely seen and robust spine-like appendages are generally truncated. They resemble Haplostigma irregularis (Schwarz) Seward from Middle to Late Devonian Lower Witteberg Group, East Cape Fold Belt, South Africa and Haplostigma furquei (Frenguelli) Gutiérrez from Precordillera Argentina. At Mataral, Angosto del Pescado and Balapuca the shales and siltstones interbedded with the Haplostigma records yielded mostly continental palynomorphs with Grandispora pseudoreticulata and other Eifelian (i.e., Densosporites inaequus, Leiotriletes balapucensis, Verrucosisporites scurrus) to Givetian species (e.g., Geminospora lemurata, Archaeozonotriletes variabilis, Chomotriletes vedugensis, Verruciretusispora ornata, Chelinospora ligurata, Samarisporites triangulatus), and less microplankton species (i.e., acritarchs, prasinophytes, chitinozoans). At Yesera Centro, the spores Acinosporites eumammillatus, Auroraspora macra, Geminospora piliformis, and the acritarchs Maranhites insulatus, Ammonidium garrasinoi, Crucidia camirense, Verhyachium pannuceum, Gorgonisphaeridium furcillatum, Gorgonisphaeridium ohioense allowed the attribution of a Givetian-Frasnian up to early Famennian age to the Haplostigma intervals. Samples from Yesera Dique were barren but the presence of Rhipidomiella sp. associated to Haplostigma allowed their correlation to Yesera Centro. [CONICET PIP 5518 (2005-2007), PIP 0305 (2011-2013)].