Trilobites from the Lejopyge laevigata Zone (Guzhangian; Upper Middle Cambrian) of the San Isidro Area, Mendoza, Argentina

Abstract

The San Isidro area is a classic fossil locality of the Lower Paleozoic of the southern Precordillera, Mendoza. The trilobites recognized to date from this area come from various stratigraphic levels of early middle Cambrian (Glossopleura and Oryctocephalus zones) and late Cambrian (Crepicephalus, Glyptagnostus reticulatus, Elvinia and Saukia zones) age. Additionally, trilobites from the Lejopyge laevigata Zone (latest middle Cambrian) is here reported from San Isidro for the first time. The assemblage studied is composed predominantly of agnostoids of great value for intercontinental correlation (Lejopyge laevigata, L. armata, Agnostus microcephalus, Ammagnostus beltensis, Clavagnostus calensis, C. repandus, Tomagnostella nepos and Diplagnostus planicauda) in association with polymeroids which, although much rarer, provide supplementary biostratigraphic information.