Systematics of Shumardiidae (trilobita), with new species from the ordovician of Argentina

New shumardiid trilobites from Arenig to Early Caradoc deposits of the Arge ntine Precordillera include species of a revised Kweichowilla (K. salasae. K. sterrenae, and K. piojensis) and the new genus Changehowilla (C. sanjuan ina and C. gracielae, and C.? carrerai), Conophrys fabiani new species occu rs in the Early Tremadoc of the western Puna region. northwestern Argentina . Leoforteyia new genus is based on L. hintzei new species from the Ibexian of Utah. Published taxa recognized as new species are Conophrys rushtoni, Conophrys wrighti, Leoforteyia ludvigseni and Shumardia whittingtoni. Phylo genetic analysis suggests the differentiation of Shumardia Billings, 1862, Kweichowilla Chang, 1964 Changchowilla new genus: and Leoforteyia new genus as separate taxa and indicates that Conophrys Callaway. 1877, is a grade g roup. Silicified material provides a nearly complete growth series for Kwei chowilla salasae, including the first protaspides known with confidence for the Shumardiidae. Additionally. ontogenetic material for K. sterrenae, C. sanjuanina, C. riojana (Benedetto and Canas) and C.? carrerai is described. Leoforteyia is restricted to the Ibexian-Whiterockian of western Laurentia species of Shumardia are widespread in the Arenig to Early Ashgill of weste rn Europe, Australia. Laurentia, China and Russia. Changehowilla is recorde d in the mid-Late Arenig-Llanvirn of the Precordillera and in the Llanvirn- middle Caradoc of China. Argentine species of Kweichowilla are closely alli ed to Australian species, suggesting biogeographic affinities of the Precor dillera to the eastern margin of Gondwana by the Llanvirn and Caradoc. Functional morphology, occurrence in fine grained sediments. and associatio n mainly with atheloptic and pelagic trilobites suggest that shumardiids we re deposit-feeders that inhabited low light levels in low energy settings. with a limited ability to burrow in soft sediments.