Solomon Isl's help.

[Tim Simmons]

Well I have found some of what I am looking for in this link. It stopped working just recently for me but I will still add it. It explains all if you take the trouble to read it. The only problem is the actual function of the piece is still unresolved although the context is now known. The club/staff is a carving depicting "Karemanua" A myth and a deity spirit guardian.

https://www.penn.museum/sites/expedi...rdian-dieties/

As mentioned the anthropomorphic aspect and now I can see that the arcs of shell inlay around the dorsal fin are to represent the streaming cordyline streamers as the shark "Karemanua" swims.