La Subzona de Periodon gladysi (Conodonta) en el Ordovícico Medio de Precordillera: su evaluación

the periodon "gladysi" subzone is defined as the lower par of the lenodus variabilis zone in the ordovician biostratigraphic scheme of argentina. the review and evaluation of conodont elements that are composing the species p. "gladysi" albanesi allow recognizing p conodont elements of microzarkodina ozarkodella lindstr？m. a nomen nudun for the species p. gladysi" and the nullity of the mentioned subzone is proposed here. besides, the presence of the species m. ozarkodella defines the upper part of the eoplacognathus pseudoplanus zone in the upper most level of san juan formation at section of cerro poterillo and portezuelo de yanso at the san juan precordillera.