The genus Prasopora (Bryozoa) from the Middle Ordovician of the Argentine Precordillera

Abundant zoaria of the discoidal to mound-shaped genus Prasopora are described from the Las Plantas and Las Aguaditas Formations in the Argentine Precordillera. Forty complete zoaria were collected from Middle Ordovician rocks, which include a graptolithic and conodont faunas belonging to the Nemagraphtus gracilis and Amorphognathus tvaerensis biozones respectively. The specimens occur in parautochtonous calcareous breccias (debris flow deposits) and autochthonous laminated mudstones and peloidal calcisiltites. Prasopora inhabited the external platform, the upper slope and probably the toe of slope, exhibiting high environmental tolerance. The genus attained a worldwide distribution by the Mid to Late Ordovician. Prasopora argentina n. sp. is described and figured and compared with the type species, P. grayae Nicholson and Etheridge from Scotland and P. discula (Coryell) from North America.