Curation of complex palaeontological objects: a case study of densely encrusted cobbles from a Japanese Pleistocene locality

Abstract

Fossils most often consist of discrete objects, such as the shell of a brachiopod, or individual bones of a vertebrate skeleton. Cataloging and labelling these specimens is relatively straightforward. However, fossil hard substrates (shells and lithoclasts) with multiple encrustations and borings made by marine organisms can present a greater challenge, as exemplified by material recently collected from a remarkable locality in northern Japan. About 6.5 metres of marine gravels belonging to the Pleistocene Setana Formation, dated at about 1 million years old, are exposed at Kuromatsunai. The well-rounded lithic clasts and associated shells are densely encrusted by well preserved bryozoans and other sclerobionts on all surfaces. Up to 25 different bryozoan species can be found on a single cobble. Full curation of such cobbles is difficult: with little or no free space for affixing labels, how can individual encrusters be indicated and catalogued? Here we present the results of our evaluation of various imaging techniques (microphotography, macrophotography, SEM, 3-D laser scanning etc), and ways of incorporating annotated images into the specimen database (KE EMu) used at the Natural History Museum. A combination of macrophotography and SEM produced the best solution in providing high resolution digital images that could be annotated and uploaded into the KE EMu database.