Acentronura Kaup, 1853

Diagnosis.— A genus of the Syngnathidae that shares numerous morphological synapomorphies with Cylix and Idiotropiscis, including head angled ventrally approximately 25° from the principal body axis, enclosed brood pouch, brood pouch plates, prehensile tail, and absence of caudal fin. However, Acentronura differs from its co-familials by the following combination of characters: supraoccipital low, not elevated, with distinct dorsomedial crest, followed by an elevated bony dimple; bilateral bony lobed protuberances on the posterolateral margins of the post-temporal bones; anterior nuchal plate absent; posterior nuchal plate present anterior to cleithrum with dorsomedial crest-like ridge along its dorsum, large gap present between the supraoccipital and posterior nuchal plate; small blunt spine midway between orbit and lobed protuberance on operculum; cleithral ring distinct, discontinuous mid-dorsally; single gill slit between supraoccipital and cleithral ridge; rim of orbit projecting dorsolaterally and slightly ventrolaterally; spines absent on principal trunk and tail ridges.

Type species.— Hippocampus gracilissimus Temminck and Schlegel, 1850 .