A skull found off the Canterbury coast - which raised suggestions that it might belong to missing teenager Olivia Hope - could have been in the water for up to 25 years.
Police say researchers at Otago University found that the skull belonged to a young anaemic female, and could have been on the seabed since the late 1970s.
The skull was found by a fishing trawler near the mouth of the Waimakariri River, north of Christchurch, in August 1999, and preliminary tests suggested it had been on the seabed for just four years.
Olivia Hope, 17, of Blenheim, was last seen boarding a yacht in the Marlborough Sounds in January 1998.
Picton man Scott Watson was sentenced to life imprisonment for murdering her and her friend Ben Smart.
