A thread-thin pipehorse, a few centimetres long and barely thicker than a hair.
Extraordinarily attenuate and very small — about 26 mm in total, thread-thin, with a conspicuously swollen trunk in both sexes and an eel-like body. Nothing else in the region looks remotely like it, so once found the identification is not in question; the difficulty is entirely in finding it. It was described in 2007 from a single adult female collected in the Lembeh Strait, and the species name honours Noldy Rumengan, the Indonesian dive guide who collected that animal and recognised it as something new.
Two things usually said about it are wrong. It is not a pygmy pipehorse. Molecular work in 2022 placed the genus as sister to the pipefish genus Urocampus, in a clade that excludes the pipehorses entirely, with supporting differences in meristics, in the ridge configuration of the trunk and tail, and in the position of the dorsal fin — so “pygmy pipedragon” and “pipehorse” are names of convenience rather than statements of relationship. And it is not a Lembeh endemic. There is a vouchered museum specimen from Okinawa, and records from the Philippines, Papua New Guinea, Fiji and the Marianas. It is reliably found in Lembeh because Lembeh guides know where to look. It anchors on bryozoans, hydroids and debris on low-relief silt bottoms between about 8 and 20 m, and individuals are reluctant to leave the spot where they are first seen, which is why a guide can show you the same animal on consecutive days.
Ratings are per location: 1 means found on most dives that look for it, 5 means a handful of records. Where enough dives have been logged the figure is calculated from them; otherwise it is an editorial estimate, and says so. We publish habitat and destination, not the dive site.