Fossil evidence for earlier radiation in istiophorid billfishes (Teleostei, Istiophoriformes) uncovered by comparative morphology of the caudal vertebrae

Billfishes include some of the largest pelagic teleostean species, but several aspects about their morphology, paleobiology, and evolution remain ambiguous. Their fossil record is fragmentary mostly represented by rostral skull remains. Here, we present a comparative study caudal vertebral morphology extant istiophorid species use this information to describe two vertebrae from Gatun Chagres formations, both late Miocene Panama. The vertebra Fm. characterized presence lateral apophysis identified as Makaira sp., while Río Indio Member lacks structure its indicates different genus. estimated total length sp. specimen 5.18 m, size calculated for marlin, Rio was 2.56 m long. Phylogenies show that radiation most living seemingly occurred during Pliocene. However, our results highlight genus taxa lacking apophyses Miocene, showing istiophorids likely before Pliocene (ca. 5 Ma).