...and was much wtf'd. The wall in that section of the museum is more an art piece than a museum installation; nothing is labeled. I figured it was some kind of pipefish, but had never seen it before; later google-guessing found that it is in fact an Ornate Ghost Pipefish.
Pipefish (Syngnathiformes) are close relatives to seahorses, and like them have long snouts and prehensile tails. Some "false" pipefish, like the ghost, are part of a subfamily that possess longer fins, giving them that very dragon-like look. Ghost pipefish spend most of their time in open water, hanging upside down and sucking tiny crustaceans in through their snouts. Like seahorses, pipefish females lay their eggs into a pouch on the male's chest or abdomen, and the male fertilizes them and takes care of the eggs. "Syngnathus" is greek for "fused jaw", referring to the pipe-like mouth and nose that they use to siphon food.
A higher res view of the ornate ghost:
"Real" pipefish are genuine Syngnathidae and are more closely related to seahorses, having few if any appendages.
Check out the tail on this African Bluestripe Pipefish:
The leafy sea dragon (which has already appeared here) is actually a pipefish, more closely related to these guys than to seahorses (subfamily Hippocampinae). There is also a more pipefish-looking Spiny Sea Dragon:
And this banded pipefish has a head that looks decidedly dragonlike also:
I like to imagine them large enough to menace frigates from the 17th century.
Moar photos (big ones). Also a photo of the Hall of Biodiversity so you can see why it was difficult to tell what anything was; this image doesn't even half capture how overwhelming and beautiful that large hall is.