Dorsal fin

I'm doing the Red Serpent's dorsal fin in sections, because it's much easier that way.  This photo shows four different sections in place, and they're made the same way I made fins for the fish project a little while ago.

Topsell described the animal as having hairs growing along the ridge of its back and under its belly, "or at the least thin small things like hairs".  He knew that fish don't have hair, and the "Red Serpent", with its gills and fins, is clearly a fish of some sort.  So what are these hairs?

I've interpreted the "hairs" as thin spines that project out from the animal's fins.  I'm not sure that they look much like hairs, but they are somewhat bristly and do at least look like something that belongs on a fish.