In August 2005, an outstanding site for fossil bryozoans was discovered at Kuromatsunai on Hokkaido, the northern island of Japan. This locality exposes marine gravels belonging to the Setana Formation of Pleistocene age. The great majority of the pebble- and cobble-sized clasts forming the gravel are encrusted by bryozoan colonies in excellent states of preservation. We are unaware of other marine gravels of any age in the geological record that contain such rich bryozoan faunas. In addition, fragments of erect bryozoans occur abundantly in the matrix between the clasts. The locality was quickly dubbed ‘Kokemushi Paradise’, kokemushi being the Japanese word for bryozoans. Aside from the bryozoans, there are also stylasterid hydrocorals, bivalves, barnacles and serpulid worms. Like the clasts, the stylasterids and bivalves, especially pectinids, are typically heavily encrusted by bryozoans.
Quarry
The diverse encrusting bryozoan fauna from Kokemushi Paradise offers unprecedented opportunities for studying the dynamics of an ancient hard substrate community, including overgrowth competition for substrate space between encrusters, patterns of fouling, short-term ecological succession on clasts, microhabitat differentiation, and the influence of clast type, size and shape on the encrusters present. In addition, palaeoenvironmental information can also be gleaned from the bryozoan fauna at Kokemushi Paradise, potentially valuable in understanding climatic and oceanographic conditions approximately one million years ago.
Quarry Clasts
The first step before interpretive research can progress on the palaeoecology and palaeoenvironment of Kokemushi Paradise is to identify the bryozoans present. As the taxonomy of bryozoans is often complex, and available literature is inadequate, scattered and sometimes difficult to obtain, there is a need for online publication of images and descriptions of the bryozoans from Kokemushi Paradise.
Shells in Quarry