ORDOVICIAN (WHITEROCK) CALYMENID AND ENCRINURID TRILOBITES FROM THE PRECORDILLERA OF ARGENTINA

Phacopida from upper Whiterock (Lower Caradoc) horizons in the Las Agu aditas Formation of San Juan Province, Argentina, include the calymeni d Platycalymene trapezoidalis (Baldis and Pothe, 1995) and the encrinu rids Frencrinuroides edseli new species, Lasaguaditas oweni new genus and species, and Walencrinuroides? new species A. Sulcocalymene Baldis and Pothe, 1995, a purported subgenus of Flexicalymene, is a junior s ubjective synonym of Platycalymene Shirley, 1936. Platycalymene is now known from Avalonia, Baltica, Laurentia (Scotland), and the Precordil lera. Emending the cladistic analysis of Ordovician Encrinurinae by Le sperance and Desbiens (1995), the monophyly and membership of Frencrin uroides and Walencrinuroides are ambiguous. Frencrinuroides edseli is closely related to species from eastern Laurentia. Lasaguaditas new ge nus is superficially cybelinid-like in some respects bur shares severa l derived characters with the Encrinurinae. All three encrinurinid spe cies in the Las Aguaditas Formation possess two instars in the protasp id period, a general pattern in Ordovician encrinurinid ontogeny.