Macroborings of Middle Ordovician age from southern Norway

The question of initial development of substrate selectivity by boring organisms is a topic that has recently aroused the interest of paleoecologists as it represents an important step in niche specialization for marine invertebrates. Kobluk, James & Pemberton (1978) suggested that the initial diversification of macroboring organisms related to the development of skeletal reefs in the Middle Ordovician and showed that substrate selectivity among some boring organisms had originated by Late Silurian time at the latest. The purpose of this note is to furnish further information on macroborings from the Middle Ordovician and to indicate that some organisms had developed several aspects of substrate selectivity during this period.