Trilobites from the Cedaria prolifica Zone (Cambrian; upper Guzhangian) of the Precordillera of Mendoza, western Argentina

Abstract

Trilobites from the upper Guzhangian of the southern Argentine Precordillera, preliminarily described by Carlos Rusconi in the 1950’s, are revised herein. The specimens studied were collected from an allochthonous limestone block of La Cruz Olistoliths at 200m NW of Estancia San Isidro locality (San Isidro area, Mendoza). Taxa comprise Kormagnostus seclusus (Walcott), Cedaria prolifica Walcott, C. puelchana Rusconi, Tricrepicephalus texanus (Shumard), Meteoraspis metra (Walcott), Coosia conicephala (Rusconi) new combination, Coosella texana? Resser, Nasocephalus cf. nasutus Wilson, and Olenoides proa (Rusconi) new combination. The North American genera Meteoraspis Resser and Nasocephalus Wilson are reported confidently from South America for the first time. This assemblage is representative of the Cedaria prolifica Zone, which correlates with the lower Crepicephalus Zone of the traditional North American genus-based zonation. Most of the genera and species identified were previously described exclusively from Canada, USA and northwestern Mexico; a fact that provides new support to an allochthonous Laurentian origin of the Argentine Precordillera.