Etalia , a new Middle Triassic (Anisian) bivalve from New Zealand, and its relationship with other pteriomorphs

The bivalve, Etalia johnstoni n. gen. et sp., is described from strata of the Etalian Stage (Anisian) of Nelson and Southland Murihiku Supergroup sequences, New Zealand. It is regarded as an early member of the Monotoidea. Hinges and hinge mechanisms of 15 other pteriomorphs are discussed: Pseudomonotis (Pseudomonotidae), Oxytoma, Meleagrinella, Maccoyella, Arctotis (Oxytomidae), Monotis , Otapiria (Monotidae), Buchia, Praebuchia, Malayomaorica, Hokonuia, ?Sichuania marwicki (Buchiidae), Asoella, Aucellina (Asoellidae), and Claraia (position unknown); a new monotoidean family, Asoellidae, is proposed. Etalia ranks with Oretia and Hokonuia in dominance and abundance in appropriate New Zealand strata. The gregarious habit of Etalia coupled with its restricted range within the Etalian Stage make it an important and useful zone fossil.