Trilobites

WAISFELD, B.G. Y N.E. VACCARI

Ordovician Fossils of Argentina

Universidad Nacional de Córdoba

Lugar: Córdoba; Año: 2003; p. 295 - 410

In comparison with other invertebrate groups the study of trilobites from Argentina have attracted considerable attention, in particular Ordovician trilobites from the Cordillera Oriental were investigated in greater detail. This may be due to the easy accessibility of many sections, for example, in the surroundings of Salta or Jujuy cities or along the Quebrada de Humahuaca, and also because of the extraordinary abundance of specimens in some of these sections. Although with some gaps trilobite research in the Cordillera Oriental was by far more sustained and largely contrasts with the scattered contributions from Precordillera, Famatina, and Puna basins. Our aim in the present review is to provide an update compilation of most published Ordovician trilobite genera and species, making available a better understanding of a considerable amount of poorly known taxa, with new criteria to identify them. Despite our efforts to achieve a review as complete as possible the reader familiar with Ordovician trilobites from Argentina will perceive that the list of species illustrated herein is not complete. There are some absences, and there are several reasons to explain these nonappearances. For example, many species included in the 1957 monograph by Harrington and Leanza Ordovician Fossils from Argentina are now known to be Cambrian in age. Those that are well documented that do not pass across the Cambrian Ordovician boundary were excluded from the present review. Concerning the trilobites from Precordillera the discovery of silicified trilobites in different Ordovician units such as Llanvirn and Caradoc horizons of Las Aguaditas Formation, Llanvirn levels of Las Chacritas Formation, and Arenig strata of the San Juan Formation and Gualcamayo Formation permitted the recovery of great amount of finely preserved material. The study of the silicified material significantly increased the number of species hitherto known for Precordillera, and also provided a wealth of information regarding other aspects concerning details of the life cycle of many trilobite taxa, phylogeny, paleoecology, and paleogeographical constraints