Cambrian agnostid communities in Tasmania



Jago, J. B.: Cambrian agnostid communities in Tasmania.

Two or possibly three different agnostid trilobite assemblages can be distinguished in the late Middle and early Upper Cambrian sequences of northern and western Tasmania. This is significant because in recent years agnostid trilobites have been widely used in local and international correlations of Middle and Upper Cambrian rocks. The three assemblages recognized are (1) an agnostid assemblage in which polymerid trilobites are abscnt, rare or present as thanatocoenotic fossils, (2) a ptychagnostid-non-nepeid assemblage, and (3) a nepeid-clavagnostid-peronopsid assemblage in which non-agnostid trilobites are abundant but ptychag-nostids are absent. It is proposed that assemblage (1) represents an open sea fauna, with assemblages (2) and (3) occurring in progressively shallower water.