PERMINERALIZED FERN STEMS FROM THE MIOCENE RANCAHUE FORMATION, NEUQUÉN PROVINCE, ARGENTINA1

CÉSARI, S.N.; VERA, E.I.; PEREZ LOINAZE, V.S.

Florianopolis, Brasil

Simposio; XII Simpósio de Paleobotânicos e Palinólogos; 2009

Asociación Latinoamericana de Paleobotánica y Palinología

The Rancahue Formation was deposited during the Miocene covering pre-tertiary units, and is overlied by Pliocene basalts of the Tipilihuque Formation. Its oucrops are located in the Andean region of the Neuquén Province, in the proximities of Aluminé city, Argentina. Previously, one of the few fossil taxa recorded and named from the unit was the tree fern Alsophilocaulis calveloi, published in the early sixties by Menendez. Recent work on the unit allowed the identification of two filicalean taxa, along with in situ angiosperm woods. One of these ferns, probably related with the Family Blechnaceae, consists of stems with amphicribal meristeles forming a dictyostele, with gaps produced by the divergence of root traces, and petiole bases containing two hippocampiform bundles flanking eight to ten small round bundles, half of them diverging of them diverging from cauline meristeles and the rest from the hippocampiform bundles. Permineralized isolated stipites referred to this taxon show an adaxial groove and a pair of pneumatophores on the lateral sides of the stipe base; and the presence of at least tripinnate fronds. The second filicalean taxa recorded in this study was a new specimen of Alsophilocaulis calveloi, which isbigger than the holotype, and preserves petiolar bases and other anatomical structures not present in the original material.