A microscopic marine creature believed to have been extinct for four million years has been found alive and well in New Zealand waters, researchers said on Thursday.

The animal, a tentacled polyp called protulophila, forms colonies inside sea worms and first appeared in the fossil record about 170 million years ago in Europe and the Middle East, government marine agency NIWA said.

The last trace of it was in rocks that were four million years old, until scientists found the organism in samples from New Zealand, half a world away from its regular habitat, which were formed just one million years ago.

That sent researchers scrambling to check more recent samples and sure enough the polyp turned up in sea worms collected by NIWA in 2008 near Picton, on New Zealand's South Island.

NIWA marine biologist Dennis Gordon said scientific "detective work" involving researchers from NIWA, Britain's Natural History Museum and the University of Oslo was responsible for the discovery.

"Finding living protulophila is a rare example of how knowledge of fossils has led to the discovery of living biodiversity. It's very exciting," he said.

He added that the next stage of research into the creature, which is related to corals and sea anemones, was to find fresh samples for gene sequencing.