The weedy seadragon was previously the only member of its genus until the discovery of its closest relative, the ruby seadragon, in 2015.
The weedy seadragon is a marine fish related to the seahorse. It’s in the subfamily Syngnathinae, which contains all pipefish. The weedy seadragon has no subspecies.
It is most closely related to the other member of its genus, the ruby seadragon (Phyllopteryx dewysea) and also the leafy seadragon (Phycodurus eques). The ribboned pipefish (Haliichthys taeniophorus) is not closely related to the weedy seadragon and does not form a true monophyletic clade with weedy and leafy seadragons.
The weedy seadragon was previously the only member of its genus until the description of the ruby seadragon in 2015.