H. histrix Kaup 1856

English common names. Thorny Seahorse, longspine seahorse, spiny seahorse.

Synonyms. H. curvicuspis Fricke 2004 (in part), H. hystrix Kaup 1856.

Distribution. Australia, China (including Province of Taiwan), French Polynesia, Guam, Hawaii, India, Indonesia, Japan, Malaysia, Mauritius, Mozambique, Micronesia, New Caledonia, Palau, Papua New Guinea, Philippines, Reunion, Samoa, Seychelles, South Africa, South Korea, Tahiti, Tanzania, Thailand, Tonga, Viet Nam.

Syntypes. MNHN A-0906, RMNH 1537.

Type locality. Japan.

Notes. Five of the eleven specimens used by Fricke (2004) to describe H. curvicuspis were examined previously by the first author who did not find the cited morphological and meristic distinctions that purportedly separate these specimens from H. histrix (Lourie et al. 1999; Appendix G). In addition, one specimen (AMS IB.4155) in the type series appeared to be a member of a different species (H. spinosissimus) (SL pers. obs.). The wide geographic range of H. histrix (from east Africa to Japan) warrants further investigation, as Song & Mabuchi (2014) suggest that the genetic distance between Indian and Pacific H. histrix is 6.6–6.7% (CO1) and this is also suggested by BOLD (2016) which indicates a 6.13% distinction between specimens from Mozambique / India versus Viet Nam / Japan (648bp CO1). This high degree of divergence indicates the presence of at least one cryptic species across the range. There are no genetic data currently available for H. jayakari, which is morphologically very similar to but replaces H. histrix in the Red Sea and Arabian Gulf.