“…Heteromorph ammonoids, represented by nostoceratids and diplomoceratids, are numerically dominant among the ammonoid assemblages from the lower-middle parts of the Hiraiso Formation and from a few horizons in the Isoai Formation (Masukawa & Ando, 2018). Although several vertebrate remains, such as a mosasaur vertebra, costals and a humerus of trionychid turtles, and shark teeth, have been found in the Isoai Formation (Figure 4;Saito, 1962;Kato et al, 2017Kato et al, , 2019Kato, Miyata, et al, 2020;Kato, Sonoda, et al, 2020), no vertebrate remains had been reported from the Hiraiso Formation previously.…”