A new tuna specimen (GenusAuxis) from the Duho Formation (middle Miocene) of South Korea

Abstract

ABSTRACTThe partially articulated caudal vertebrae of a tuna were discovered from the Duho Formation (middle Miocene) of South Korea. This specimen was assigned to the genusAuxisand represents the second record of fossilAuxisfound in South Korea. We compared the vertebral morphology of the studied specimen to that of currently known species ofAuxis, including extinct taxa, but the specimen is not assigned to a new or existing species ofAuxisdue to poor preservation and a lack of diagnostic features. The discovery of a new specimen ofAuxissupports theories of high marine biodiversity in the East Sea (Sea of Japan) and the opening of the East Sea in the early to middle Miocene. A widely opened East Sea might have increased the abundance and diversity of large oceanic fishes such as tunas during the deposition of the Duho Formation. A taphonomic scenario of the specimen was inferred based on the lack of anal pterygiophores and the leaf imprint on the matrix. The specimen would have been exposed for at least a month in a low-energy sedimentary environment at the deep-sea bottom and undergone disintegration before being buried.