ONTOGENY AND RELATIONSHIPS OF THE ORDOVICIAN ODONTOPLEURID TRILOBITE CERATOCARA, WITH NEW SPECIES FROM ARGENTINA AND NEW-YORK

A growth series is described for a new species of Ceratocara Ramskold, 1991, C. argentina, from the Upper Ordovician (Caradoc) part of the L as Aguaditas Formation, near Jachal in San Juan Province, Argentine Pr ecordillera. Another new species of Ceratocara, C. shawl, is described from the Middle Ordovician (lower Chazy) Crown Point Formation of New York. A phylogenetic analysis is presented for these species, other w ell-known Ordovician species of Ceratocara, and some Ordovician specie s of Ceratocephala, with Ceratocephalina tridens Whittington, 1956, as outgroup. The analysis presented supports the monophyly of both Cerat ocara and Ceratocephala Warder, 1838, their divergence having occurred by the middle Arenig. The ontogenies of the Ceratocara species from A rgentina and New York, complete from protaspid to holaspid growth stag es, are some of the best preserved odontopleurid ontogenies described to date. Material of Ceratocephala triacantheis Whittington and Evitt, 1954, from the Crown Point Formation of the Chazy Group of New York, is discriminated from that of Ceratocara shawl.