Notes on the taphonomy and paleoecology of New Zealand tertiary spatangoida

Abstract

The distribution of spatangoid echinoids and molluscs in New Zealand Tertiary formations is anomalous; formations relatively rich in spatangoids are poor in molluscs and vice versa. The absence of Mollusca from spatangoid-rich formations is attributed to diagenetic dissolution of aragonitic shells while the stabilisation of spatangoid magnesium calcite is attributed to incongruent dissolution. Irregular bevelled perforations in some spatangoid tests are attributed to predation by tonnacean gastropods such as Echinopboria and large Austrosassia. New Zealand Tertiary spatangoids are of little use as depth indicators as those genera still living have large depth ranges.