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Six angiosperm pollen types studied with SEM are recorded in the Cretaceous (early Aptian) Ticö flora on the basis of material recovered from two localities: Anfiteatro de Tico and Bajo Tigre. Clavatipollenites dominates, with four types described. The other two types, based on single specimens, were referred to Retimonocolpites and to the Anacostia type. Comparisons are made with similar species found in other Cretaceous paleofloristic regions and with other Aptian pollen assemblages from Patagonia. The chlorantha-ceous affinity of Clavatipollenites agrees with known paleobotanical, sedimentological, and paleoclimatical data obtained for the same fossiliferous horizons of the Anfiteatro de Ticö Formation studied here. During the early Aptian, a warm and humid paleoclimatic belt extended to latitudes greater than 60°S in SW Gondwana. This belt is known to have persisted until the late Aptian in southern Patagonia. The angiosperm pollen variety is further underscored by fossil leaves found in two of the horizons studied here, suggesting that angiosperms may have existed during the Barremian in SW Gondwana (Patagonian Province). [ABSTRACT FROM AUTHOR]

Abstract: The araucarian pollen grain Cyclusphaera radiata Archangelsky is emended based on newly discovered material from the Piedra Clavada Formation of Albian age in Santa Cruz province, Argentina. The general morphology and ultrastructure of the pollen were studied by means of transmitted light, scanning, and transmission electron microscopy. C. radiata is discoid with an equatorial thickening and two large opposite apertures, with radial thickenings in one of them and two central apertural occlusive opercula-like structures. Beneath there is a thick amorphous electron-dense nexine. The combination of characters seen in this pollen type is very unusual, and no parallels are known in fossil or extant gymnosperm grains. Functional interpretation of the apertural exine suggests that the radial thickenings and apertural membranes were involved in harmomegthy, the opercula-like structures in germination, and the apertural nexine perhaps as a strengthening layer. A hypothetical pollination mechanism is also presented for C. radiata. The paleobiogeography of this taxon shows that during the Mesozoic, the plants that produced these grains inhabited an extensive area of Gondwana that included South America, Africa, India and Antarctica. [Copyright &y& Elsevier]