Unknown New Zealand Miocene marine bone

[Entoloma]

Hi all! I found an unassuming concretion at Glenafric in New Zealand (Marine deposit 12 - 10 million years old). I almost left it on the beach, but the concretion was small, and this small bit showing (which I thought it could be phosphorus or degraded pyrite) looked plausible for bone. Anyway, I popped it in my pack and forgot about it for a week.

I only remembered it yesterday when I was with some friends and they entertained the prospect that it could be a Dolphin tooth. When under magnification, it was clear that it was bone.

 

 

Today I started prepping it and uncovered quite a lot. Does anybody have a clue to what this bone may be? Could it be fish? Penguin, Seal? I dont know.

 

Edited August 19 by Entoloma

[Doctor Mud]

I think fish for this but don’t immediately recognize which bones apart from circled which looks like a vert. Edit or is that an illusion from scribe marks in matrix above bone. Looks like vertical “struts” in fish vert

 

the rest looks like skull elements. Operculum? Maybe too thick for that? Neurocranium? 
 

looks interesting- I’d keep on prepping. 
 

Edited August 20 by Doctor Mud