The jagged teeth of a hefty predator that lived in our waters 80 million years ago have been discovered in a Hawkes Bay forest.
The fossil remains of a mosasaur - a large marine reptile that was a dominant predator toward the end of the Cretaceous period - have been identified by experts at GNS Science after being earlier found in Maungataniwha Native Forest.
Earlier this year, Forest Lifeforce Restoration Trust forest manager Pete Shaw and Department of Conservation biodiversity ranger Helen Jonas had been searching for whio (blue duck) up a small stream, when they 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 nearby pool to fetch a branch with which to lever the rock loose.
While in the pool, Mr Shaw felt something rough and lifted out another rock containing the fossilised jaw fragment.
"There was great jubilation at that point," Mr Shaw said.
The mosasaur could be likened to a crocodile with a snake-like body and paddle-like appendages.
It is believed to have lived only in water.
The area where the teeth were found is known by geologists as a hot-spot for fossils, and was where renowned palaeontologist Joan Wiffen famously first discovered evidence of land-dinosaur fossils in New Zealand, changing a long-held view that dinosaurs never existed here.
While mosasaur fossils have been found before in New Zealand - including around the forest area - they are not particularly common.
The first discoveries were in the Waipara, followed by others at Shag Point in Otago and Haumuri Bluff in southern Marlborough.
GNS Science collections manager John 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 remained hidden in the rock.
The digital model would then be sent to experts in Canada in a bid to identify the species of mosasaur.
"We're interested to find out as much as we can," Mr Simes said.
"Who knows what Pete might have stumbled across. These teeth are twice the size of anything Joan found."