Researchers have found a fossil with bite.

Teeth from an ancient marine predator is the latest find to come from Maungataniwha Native Forest, inland Hawke's Bay.

Scientists from Wellington-based GNS Science said the teeth came from a "nasty" predator with a bad attitude from about 80 million years ago. The beast has been identified as a mosasaur, but the exact species was yet to be determined.

Mosasaurs were large marine reptiles and were the dominant marine predators during the last 20 million years of the Cretaceous period.

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While mosasaur fossils have been discovered before in New Zealand they were not common, GNS collections manager John Simes said.

Fossilised mosasaur teeth were among the many discoveries made from the mid-1970s onwards by celebrated New Zealand palaeontologist Joan Wiffen in the Mangahouanga Stream in Hawke's Bay. She first discovered evidence of land-dinosaur fossils in New Zealand there and the area has been delivering interesting discoveries since.

Maungataniwha is owned by the Forest Lifeforce Restoration Trust which provides direction and funding for the restoration of threatened species of fauna and flora in native forests.

Forest manager Pete Shaw and DoC biodiversity ranger Helen Jonas were conducting a search for whio (blue duck) up a small stream and spotted a rock with a lump of bone in it.

Ms Jonas was keen to see if the bone extended through the rock so Mr Shaw jumped into a pool to fetch a branch with which to lever the rock loose.

While in the pool Shaw felt something rough and lifted out another rock containing the fossilised jaw fragment. "There was great jubilation at that point," Mr Shaw said.

Mr Simes said he hoped to have a medical CT scan done of the fragment in order to create a digital 3D model of the teeth, most of which was still hidden in the rock. This digital model would be sent to experts in Canada in a bid to identify the species of mosasaur.