Ordovician cheirurid trilobites from the Argentine Precordillera

New cheirurid trilobite species from the Las Aguaditas Formation in San Juan Province include the Llanvirn Macrogrammus rafi, and the Early Caradoc Ceraurinella zhoui, Nieszkowskia jakei, and N. yongyii. Precordilleran species, such as the Llanvirn Macrogrammus pengi new species from the Gualcamayo Formation, reinforce sinoparapilekiinid affinities for the poorly known Macrogrammus Whittard, 1966, although the monophyly of Sinoparapilekiini requires corroboration. The ontogeny of Ceraurinella zhoui confirms the presence of early protaspid stages for this genus (and Cheirurinae in general). Rare cheirurids include species of Heliomeroides, Pateraspis, and an additional acanthoparyphinid.