Kainella Walcott (trilobita, Early Ordovician) In Northwestern Argentina And Southern bolivia. Biostratigraphic Significance. The Tremadocian Kainella meridionalis Zone in the Central Andean Basin is is reassessed. This zone has been widely used for regional and intercontinental correlations, but such correlations mostly involved an extended interval that corresponds, in fact, to the whole range of the genus. Species of Kainella recorded in northwestern Argentina and southern Bolivia exhibit a relatively wide geographic distribution and a constrained stratigraphic range. On the basis of their record a succession of biozones is proposed, ranging from the basal Tremadocian to possibly the early middle Tremadocian. Three biozones are proposed on the basis of integrated information drawn from several localities, i.e., the K. andina, K. meridionalis, and K. teiichii zones. In addition, the Jujuyaspis keideli Subzone is here upgraded to the rank of zone. The definition of this succession of biozones is a significant progress in the establishment of a high resolution biostratigraphic framework based on trilobites, leading to more precise correlations in the future.