Ordovician trimerellacean brachiopod shell beds

The large, thick-shelled, inarticulate brachiopod Eodinobolus forms many conspicuous deposits of shells in the Upper Ordovician limestones of central western New South Wales. Both in situ and reworked shell beds are preserved at recurrent intervals through the successions, in similar facies of both transgressive and regressive phases of deposition. In situ shell beds are best developed in transgressive sequences. These monotypic and very low diversity shell beds are interpreted as having formed in marginal marine, quiet water conditions. Eodinobolus, in its role as the dominant member of the respective pioneer community, colonized substrates in the low energy mud zone. This appears to suggest depositional environments most directly analogous to those of Palaeozoic virgianid pentamerides, and perhaps also comparable with some modern marginal marine oyster and mussel-bed occurrences.-from Authors