NOTAS SOBRE LA FLORA FÓSIL DE LA ZONA DE TICÓ, PROVINCIA DE SANTA CRUZ. X. DOS NUEVAS ESPECIES DE PSEUDOCTENIS (CYCADALES)

Sergio Archangelsky, Alicia Baldoni

Abstract


Two new species of the genus Pseudoctenis are described: P. dentata and P. crassa. Both were found' in Bajo Grande, in the Araucarites bed (Baqueró Formation, Barremian). P. dentata shows some rather unique characters for the genus: presence of stomata on the upper epidermis, sinuous cell walls and pinnae with dentate apices. Yet, some of them have already been mentioned for other species of the genus, and therefore Are considered here to be rare within the range of pseudoctenis, there is also some resemblance to the Bennettitalean genus Pteropbyllum, but the haplochilic stoma allows to relate the species to the cycadales. Dorsal lamellae of the guard cells in the stomata have been observed. The other species, P. crassa, was studied with the ordinary microscope as well as with the Stereoscan. It shows the remarkable two types of epidermal cells with thick and thin walls, and also many trichome bases and hairs. Stomata are not irequent on the lower epidermis, some also showing the remnants of dorsal lamellae on the guard cells. The number of cycadalean taxa has now increased to 10 species in the Ticó flora, this group being next in ímportance to the coniferales and bennettitales.

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