Determinación xilológica de la madera fósil de una Fagácea, de la Formación Río Turbio, (Eoceno), Santa Cruz, Argentina



The xylem structure of a silicified fossil branch fragment was studied. The age of
the .plantiferous bed, after Hünicken (1966), Archangelsky (1969) and Romero (1m), is middle or late Eocene. The xylem presents a subcircular porosity; the vessel elements are moderately short with simple perforation plates in spring vessels, and few scalariform in small vessels, The intervascular pitting is alternate, with onlya sligth tendency to be opposite. The axial parenchyma is scarce and rays are heterocellular, uni, biseriate or incompletelybiseriate. The fossil was compared with wood of living species of Nothofagus, among them with N. procera (Poepp. and Endl.jOerst., and with some fossilspecies of
Notbofagaxylon; previously studied by different authors, showing to be more similar to N. procera. This fossil wood is determined as a new species of Nothofagaxylon, namely, N. paraprocera, to stress the likeness with the extant wood.

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