Neither the spherical to subspherical shape or large size of the Moeraki Boulders is unique to them. Virtually identical spherical boulders, called Koutu Boulders, are found on the beaches, in the cliffs, and beneath the surface inland of the shore of Hokianga Harbour, North Island, New Zealand, between Koutu and Kauwhare points. Like the Moeraki Boulders, the Koutu Boulders are large, reaching in diameter, and almost spherical. Similar boulder-size concretions, known as Katiki Boulders, are also found on the north-facing shore of Shag Point some south of where the Moeraki Boulders are found. These concretions occur as both spherical cannonball concretions and flat, disk-shaped or oval concretions. Unlike the Moeraki boulders, some of these concretions contain the bones of mosasaurs and plesiosaurs.