Ordovician pliomerid and prosopiscid trilobites from Argentina

Pliomerina Chugaeva, 1958, a characteristic element of the peri-Gondwanan E okosovopeltis-Pliomerina Province, occurs in Llanvirn and Caradoc strata of the Argentine Precordillera. Three protaspid instars are present in the on togeny of the Early Caradoc Pliomerina peripata new species. A species poss ibly representing Pliomerella is a rare element in Early Caradoc strata of the Las Aguaditas Formation. Prosopiscus is represented by a Llanvirn speci es with a first record of protaspid larvae for the enigmatic Family Prosopi scidae. Early growth stages support closest relations of prosopiscids to Ph acopina. The presence of Pliomerina and Prosopiscus, along with the cheirur id Pateraspis, demonstrates a peri-Gondwanan influence on the Precordillera n fauna by the Llanvirn, and supports the proximity of the Precordillera te rrane to the South American margin by that time.