Dinosaur Poo?

Well it could be. Have you seen a goat's poo? Yes its round, black in colour.
This Moeraki boulders are black in colour, round and of mudstone.
The ones on the beach are exposed by the erosion and waves. There are a lot more, i have seen 2 more above the water line.
Amazingly only on this stretch of beach, less than a mile. Nowhere else.