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The La Laja Formation lies exposed almost continuously along the western margin of two hill ranges, i.e., the Sierra Chica de Zonda and Sierra de Villicum. This limestone unit bears a remarkable fauna of Cambrian trilobites. In this work we analyse the Delamaran trilobite fauna from the upper part of the El Estero Member and the lower third of the Soldano Member of the La Laja Formation. Taxa described are Glossopleura walcotti Poulsen, Glossopleura lodensis (Clark), Fieldaspis sp., and Prozacanthoides zondaensis n. sp. The Poliella denticulata, Mexicella mexicana?, and Glossopleura walcotti Zones are documented; these had been previously included in a hiatus. Trilobites-based correlations are established between the La Laja Formation and olistoliths of the Western Precordillera. Additional correlations are also suggested between the Precordillera and different localities in Laurentia. Finally, we discuss the biogeographic implications of the described material. Delamaran taxa reported from the La Laja Formation are characteristic and so far restricted to Laurentia. Analysis of the trilobite fauna from this unit supports the allochtonous origin of the Precordillera.

Kainella Walcott, 1925 (Trilobita, Early Ordovician) in Northwestern Argentina and Southern Bolivia. Systematic Paleontology. A taxonomic study is presented involving different species of Kainella from the Central Andean Basin. These early Tremadocian species come from the Santa Rosita, Cardonal, and Devendeus formations, and also from the Guayoc Chico Group; all units lie exposed at numerous localities in the Argentine Cordillera Oriental. Also analyzed are Kainella species from the Iscayachi Formation exposed in the Yunchara Segment in southern Bolivia. A group of eight species is recognized, suggesting a significantly greater diversity than previously assessed. An emmended diagnosis of K. meridionalis Kobayashi is provided, and a lectotype is designated. On this basis, some of the former assignments to this species are now rearranged into the taxa described herein. Complete morphological information is provided on K. andina Suarez Soruco, based on new collections from its type locality (Cuesta...

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 i...

The early late Tremadocian (Tr2) interval is exceptionally well-represented in eastern areas of the Argentine Cordillera Oriental. New field collections and detailed taxonomic reassessments, as well as a reevaluation of regional data, permit the development of a highly resolved trilobite-based biostratigraphic framework. The concept of the traditional Bienvillia tetragonalis biozone is emended and the new Asaphellus nazarenensis biozone is proposed. Hence, the Tr2 interval encompasses a succession of four trilobite biozones including in ascending order the Kainella teiichii, the Bienvillia tetragonalis, the Asaphellus nazarenensis, and the Notopeltis orthometopa biozones. This resolution is notably higher than that provided by biostratigraphically significant groups such as graptolites and conodonts, and allows a detailed basinwide correlation. New taxonomic information on A. nazarenensis Tortello and Esteban and N. orthometopa (Harrington), is provided and the new species Asaphellus albae sp. nov. is defined. Detailed correlation of the trilobite fauna from the Tr2 interval with that of other paleocontinents is difficult. Taxa are mostly endemic or display wide geographic distributions but with long stratigraphic ranges. Overall, both trilobite-based and indirect international correlations highlight that this interval is hardly recognized, incompletely preserved, or the trilobite fauna is poorly known in most areas of Gondwana. Consequently, due to the completeness of the stratigraphic and fossil records of the Tr2 in the Cordillera Oriental, this region represents a global reference site for the study of this interval. El intervalo Tremadociano temprano tardío (Tr2) está excepcionalmente representado en la Cordillera Oriental, en sus flancos oriental y central. Nuevas colecciones, una revisión taxonómica moderna y la reevaluación de datos regionales, permitieron desarrollar un esquema bioestratigráfico de alta resolución con trilobites. Se modifica el concepto de la clásica biozona de Bienvillia tetragonalis y se establece una nueva unidad, la biozona de Asaphellus nazarenensis. Por lo tanto, el intervalo Tr2 presenta una sucesión de cuatro biozonas de trilobites, en orden ascendente: Kainella teiichii, Bienvillia tetragonalis, Asaphellus nazarenensis y Notopeltis orthometopa. El grado de resolución de este esquema duplica aquél de otros grupos de importancia bioestratigráfica como graptolitos y conodontes, permitiendo de esta manera mayores precisiones en la correlación regional. Asimismo, se brinda nueva información sobre las especies A. nazarenensis Tortello y Esteban y N. orthometopa (Harrington), y se define una nueva especie de asáfido: Asaphellus albae sp. nov. La posibilidad de correlación con sucesiones de otros paleocontinentes para el Tr2 es limitada ya que la mayoría de los taxa son endémicos, o bien presentan una distribución geográfica amplia pero frecuentmente, extensos rangos. Finalmente, tanto las correlaciones basadas en trilobites como aquéllas indirectas sugieren que el intervalo Tr2 es difícil de reconocer, su registro es fragmentario y/ o la fauna de trilobites es pobremente conocida en gran parte de Gondwana. Por lo tanto, dado el completo registro estratigráfico y paleontológico del Tr2 en la Cordillera Oriental, ésta constituye un sitio de referencia a nivel mundial para el estudio de este intervalo. Fil: Meroi Arcerito, Facundo René. Instituto de Investigaciones en Biodiversidad y Biotecnología , Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Mar del Plata (Grupo de entomología edáfica bonaerense subooriental), Mar del Plata; Argentina Fil: Waisfeld, Beatriz Graciela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones Paleobiológicas; Argentina Fil: Vaccari, Norberto Emilio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones Paleobiológicas; Argentina Fil: Muñoz, Diego Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Centro de Investigaciones en Ciencias de la Tierra. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones en Ciencias de la Tierra; Argentina. Universidad Nacional de Córdoba. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones Paleobiológicas; Argentina