An individual of baleen whale remains from a Holocene sediment in Osaka, Japan was examined in 1976. It was identified as “a fin or blue whale”. Here, the specimen is described and identified as a fin whale based on the cranium, periotic, and newly added mandibular condyle features. In posterior view, the mandibular condyles of blue whales are wider than other rorquals. The mandibular condyle is structurally massive and frequently preserved, and taxonomically informative element that can be used to distinguish fin whales from blue whales. The fin whale remains emphasized that fossil specimens as well as modern strandings of fin whale are few around the Seto Inland Sea. However, the numbers are relatively high near the entrances of the Seto Inland Sea, such as Osaka Bay. More reports of well preserved specimens allowing species identification from Holocene sediments are required to reconstruct the history of whales from the past to present.

Published online 20 May, 2024; Print publication 31 July, 2024