抄録
A new species of a fossil bonito, Gymnosarda prisca (Scombridae, Perciformes) from the Early Tertiary shows an interesting combination of characters not seen in other, Recent, bonitos. The new species is based on hypural bones from the caudal region. Although a bonito, the fossil hypural plates possess a caudal notch, a character not known in Recent bonitos. The discovery of this new taxon causes a redefinition of the synapomorphies of the caudal region that define bonitos and their relatives, the tunas and Spanish mackerels. The fossil species has previously been described as part of Scomberomorus saevus.
