Eodelphis kabatensis, a new name for the oldest true dolphin Stenella kabatensis Horikawa, 1977 (Cetacea, Odontoceti, Delphinidae), from the upper Miocene of Japan, and the phylogeny and paleobiogeography of Delphinoidea

Figures & data

Table 1 Valid fossil delphinid species that have been discovered with the skull.

Species	Country	Age
Eodelphis kabatensis (Horikawa, 1977)	Japan	late Miocene
Arimidelphis sorbinii Bianucci, 2005	Italy	Plio-Pleistocene
Astadelphis gastaldii (Brandt, 1874)	Italy	Pliocene
Australodelphis mirus Fordyce et al., 2002	Antarctica	early Pliocene
Etruridelphis giulii (Lawley, 1876)	Italy	Pliocene
Hemisyntrachelus cortesii (Fischer, 1829)	Italy	Pliocene
Hemisyntrachelus oligodon (Pilleri and Siber, 1989)	Italy	early Pliocene
Lagenorhynchus harmatuki Whitmore and Kaltenbach, 2008	USA	early Pliocene
Orcinus citoniensies (Capellini, 1883)	Italy	Plio-Pleistocene
Protoglobicephala mexicana Aguirre-Fernández et al., 2009	Mexico	late Pliocene
Septidelphis morii Bianucci, 2013	Italy	Pliocene
Stenella rayi Whitmore and Kaltenbach, 2008	USA	early Pliocene
Tursiops osennae Simonelli, 1911	Italy	Pleistocene

Figure 1 The type locality of Eodelphis kabatensis (Horikawa, 1977), HMH 68037, and age of the Mashike Formation and correlated Neogene marine deposits of Hokkaido. The geological map was modified from Sato et al. (1964). The correlation of Neogene marine deposits of Hokkaido based on (Sagayama, 2000). Neogene North Pacific diatom biohorizons are based on Yanagisawa and Akiba (1998).

Figure 2 The skull of the holotype of Eodelphis kabatensis (Horikawa, 1977), HMH 68037. Photograph of the holotype skull whitened with ammonium chloride. A, dorsal view; B, left lateral view.

Figure 3 The skull of the holotype of Eodelphis kabatensis (Horikawa, 1977), HMH 68037. Photograph of the holotype skull whitened with ammonium chloride. A, anterior view; B, anteroventral view.

Figure 4 The skull of the holotype of Eodelphis kabatensis (Horikawa, 1977), HMH 68037. Photograph of the holotype skull whitened with ammonium chloride. A, ventral view; B, ventrolateral view.

Figure 5 The left periotic (A–G) and tympanic (H­–M) bulla of the holotype of Eodelphis kabatensis (Horikawa, 1977), HMH 68037, whitened with ammonium chloride. A, H, medial; B, I, dorsal; C, J, anterior; D, K, lateral; E, F, L, ventral; F, M, posterior views.

Figure 6 Left mandible (A), isolated tooth (B), basihyal + thyrohyals (C), and left stylohyal (D) of the holotype of Eodelphis kabatensis (Horikawa, 1977), HMH 68037. A, lateral; B, medial or distal; C, ventral; D, lateral views.

Figure 7 Morphological cladistic and paleobiogeographic analysis of Delphinidae and relationships of Eodelphis kabatensis (Horikawa, 1977). The strict consensus of 1734 most parsimonious trees, found by tree bisection-reconnection. Decay indices are indicated above the nodes. Taxa are parenthesized by quotation marks are paraphyletic or polyphyletic taxa.

Figure 8 Morphological cladistic and paleobiogeographic analyses of Delphinidae and relationships of Eodelphis kabatensis (Horikawa, 1977) under the constraint tree of molecular phylogenetic analysis. The Adams consensus of 68 most parsimonious trees, found by tree bisection-reconnection.

Figure 9 Comparisons of the skull of Eodelphis kabatensis (Horikawa, 1977), HMH 68037, with related delphinids. Illustrations from photographs of skulls in dorsal view (A–D). A, E. kabatensis; B, Hemisyntrachelus cortesii, MPST specimen B; C, H. oligodon, SMNK-PAL 3841; D, Orcinus orca, NMNS-M 4510.

Figure 10 The temporal and spatial distributions of Delphinoidea and related species (other delphinidans) based on the morphological cladistic analysis. *indicates molecular age from McGowen et al. (2009). Abbreviations: Aquit. Aquitanian; Ca, Calabrian; G, Gelasian; H, Holocene; Lang, Langhian; M, Middle and Upper; Mes, Messinian; Pi, Piacenzian; Plei, Pleistocene; Plio, Pliocene; Serr, Serravallian; Zan, Zanclean.

Figure 11 The temporal and spatial distributions of Delphinoidea and related species (other delphinidans) based on the morphological cladistic analysis under the constraint tree. Abbreviations are same as in Figure 10.

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