Past biodiversity: Historical Japanese illustrations document the distribution of whales and their epibiotic barnacles

In recent centuries, excessive fishing has been a major driver in the decline of marine animals. To manage and restore ecosystems, it is necessary to determine the richness of past biodiversity. This report describes the whales and barnacles recorded in classic monographs (called Honzou Gaku) written by Japanese naturalists in the 18th–19th centuries. Past Japanese fauna and flora were documented in these monographs with detailed illustrations; however, many such monographs have been neglected by modern biologists. The whale barnacles illustrated in these monographs were identified as Coronula diadema (Linnaeus, 1767), Coronula reginae Darwin, 1854, and Conchoderma auritum (Linnaeus, 1767). A case study of historical biodiversity is presented here, and shows just one example of the many organisms recorded in the Honzou Gaku. Such information has important implications for the use of historical works to assess past or lost biodiversity all over the world.