Una nueva Equisetaceae fértil de la Formación La Matilde, Jurásico Medio, Argentina

here we describe impressions of vegetative and fertile organs of equisetaceae coming from the monumento natural bosques petrificados locality, la matilde formation (middle jurassic), santa cruz province. they are very frequent in tuffaceous laminated levels with assymmetrical ripple marks, micro-crossbedding and bioturbations associated with shallow lacustrine environment. stems are herbaceous, grass-like and have extremely small dimensions: diameter 1,3 mm, internodes 0,9 cm long, cross section hexagonal with 6 carinae and valeculae and 6 leaves per node fused into a leaf sheath. no branching was observed. the material is mostly vegetative, but three specimens with mature strobili show hexagonal, verticilate sporangiophores. the observed characters allow us to assign them to a new species of equisetites: e. minimus n.sp. the stems lie parallel to the bedding planes or cross them suggesting life position. they probably grew in dense, monotypic communities, with an essentially vegetative reproduction.