Permian Pectinacea and Limacea (Bivalvia) from New Zealand

About 130 refs; 6 figs; 25 tables; 25 plates

Thirty-seven species of Pectinacea and one of Limacea are described from the New Zealand Permian. New genera are <Fletcheripecten>, <Glabripecten>, <Corrugopecten>, and <Undopecten>. Nine new species and one new subspecies are described from New Zealand, and one new species and one new name from eastern Australia. Two new subfamilies (Etheripectininae, Otapiriinae) are proposed, and four superspecies are distinguished. In the New Zealand Permian the Pectinacea were a minor element in many faunas, second only to Atomodesminae amongst Bivalvia in abundance, but much less numerous than bryozoans or brachiopods, and often gastropods. They prefered offshore sandstone, but are found as rare specimens in a variety of sediment, generally as left valves. Autecology and synecology are summarised for each species. Almost all have a well developed byssal notch, as though they lived attached to the seafloor, but species of <Etheripecten> may have been free-swimming at least for part of their life because they had a planoconvex profile and thin shell. The world distribution and diversity of genera add support to the brachiopods for calibrating Permian paleolatitudes, but Pectinacean genera from the north-west United States are anomolously diverse. Low diversities are found in east Australia, New Zealand, and north-east Siberia, and maximal diversities lie north of the present equator, in China, and especially Texas and the central United States. The probability that New Zealand occupied moderately high latitudes with cool temperatures during the Permian period may explain why the Pectinacean shell appears to have been composed entirely of calcite, in contrast to Permian Pectinacea from the United States, which have an aragonitic layer. (auth/EKS)