Middle-Late Jurassic bivalves of the superfamily Veneroidea from New Zealand and New Caledonia

Bivalves of the families Arcticidae, Isocyprinidae n. fam., and Veneridae are described from the Middle-Late Jurassic of New Zealand and New Caledonia. Morphology of shells from several genera in Arcticidae, Isocyprinidae, Veniellidae n. fam., and Veneridae is analysed in detail. These families are shown to be closely related in terms of morphological shell characters, especially ontogenetic and evolutionary hinge development. This is highlighted by identical ranges in commissural outline and shell form together with similar strength and form of ornamentation, and the fact that hinge plate development is an uninterrupted evolutionary process between Arcticidae and Isocyprinidae to Veneridae. These converging lineages show that Veneridae is at least diphyletic. This same evolutionary process is also shown to be an ontogenetic function of shells, with the final state of hinge development limited by maximum shell size. The family Corbiculidae is considered to be a major offshoot from one of the two lineages defined by Arcticidae-Veneridae or Isocyprinidae-Veneridae. These factors justify the superfamilies Arcticoidea and Corbiculoidea being synonymised with Veneroidea. In New Zealand, Isocyprinidae is represented by Austrocyprina n. gen. (one species). Veneridae is present in the form of Eocallista (one new species), and Austrocardilanx n. gen. (two new species). Arcticidae has been recorded from New Zealand and New Caledonia, and is represented by Antarctica n. gen. (one species).