Hippocampus japapigu, UW 157506, female holotype directly after collection, 16.33 mm SL, Hachijo-jima Island, Izu Islands, Japan (photograph Hiroyuki Motomura).

Hippocampus japapigu, paratypes directly after collection (A) UW 157507, male, 15.59 mm SL (B) KAUM-I. 111770, female, 14.54 mm SL, Hachijo-jima Island, Izu Islands, Japan (photographs Hiroyuki Motomura).

Hippocampus japapigu, UW 157506, preserved female holotype, 16.33 mm SL (left), and UW 157506, 15.59 mm SL, male paratype (right), Hachijo-jima Island, Izu Islands, Japan (photograph Graham Short).

Hippocampus japapigu in situ, Hachijo-jima Island, Izu Islands, Japan at 15 m depth (photograph Richard Smith).

Hippocampus japapigu in situ, Hachijo-jima Island, Izu Islands, Japan from 10 m depth (photograph Richard Smith).

YouTube video of a pair of specimens of Hippocampus japapigu on rocky reef wall (video by Akira Bingoeral 2007)

Hippocampus pontohi, AMS I.47833-001, preserved male non-type, 13.9 mm SL, Cape Kri, Raja Ampat, Indonesia (photograph Graham Short).

Comparison of live specimens of A Hippocampus japapigu photographed off Hachijo-jima Island, Japan (Richard Smith), and its most similar congener B Hippocampus pontohi photographed off Tomia Island, southeast Sulawesi, Indonesia (Richard Smith). Note the differences in the anterodorsal area of the trunk in H. japapigu vs. H. pontohi: single vs. double pair of bilaterally paired wing-like protrusions behind the head, raised dorsal ridge vs. laterodorsal flat surface, and large and prominent vs. small eighth lateral trunk ridge spine. Abbreviations: SP-WP, single pair of bilaterally paired wing-like protrusions; DP-WP, double pair of bilaterally paired wing-like protrusions; DR, raised dorsal ridge; FS, flat dorsal surface; P-8LTR, prominent eighth lateral trunk ridge spine; S-8LTR, small eighth lateral trunk ridge spine.

Comparison of the lateral view of reconstructed μCT scans of skeletons of A Hippocampus japapigu, UW 157506, preserved male holotype, 16.33 mm SL, Hachijo-jima Island, Japan, and its most similar congener B Hippocampus pontohi, AMS I.47833-001, preserved male non-type 13.9 mm SL, Cape Kri, Raja Ampat, Indonesia (photographs Graham Short).

Computed tomography scanned anterior trunk area of Hippocampus japapigu, UW 157506, male holotype, 16.33 mm SL, Hachijo-jima Island, Japan (photograph Graham Short). A Anterolateral view B Lateral view. Note the pair of spines projecting dorsolaterad on STrR1 and triangular bony mounds arched dorsad on STrR2, STrR3, and STrR4. Abbreviations: CL, cliethral ring; STrR1, first superior trunk ridge; STrR2, second superior trunk ridge; STrR3, third superior trunk ridge; STrR4, fourth superior trunk ridge; STrR5, fifth superior trunk ridge; STrR6, sixth superior trunk ridge.

Computed tomography scanned anterior trunk area of Hippocampus pontohi, AMS I.47833-001, preserved male non-type, 16.33 mm SL, Cape Kri, Raja Ampat, Indonesia (photograph Graham Short). A Anterolateral view B Dorsal view. Note the double pair of spines projecting dorsolaterad on STrR1 and STrR1, respectively, and laterodorsal surface flat on STrR3, and STrR4. Abbreviations: CO, coronet; CL, cliethral ring; STrR1, first superior trunk ridge; STrR2, second superior trunk ridge; STrR3, third superior trunk ridge; STrR4, fourth superior trunk ridge; STrR5, fifth superior trunk ridge; STrR6, sixth superior trunk ridge.