A moa skeleton sold in Britain for $51,986 this week, sparking questions about laws protecting New Zealand antiquities.
The rare complete skeleton of the extinct flightless native New Zealand bird was sold through Summers Place Auctions in West Sussex.
The auction house said the pre-15th century fully-articulated bird skeleton was from a private collection.
The moa skeleton, which stands 114cm high, was sold alongside a mammoth skeleton from Siberia, which also went to a private buyer.
Canterbury University palaeontologist Richard Holdaway said moa bones regularly came up in auctions overseas and on Trade Me.
"Irreplaceable national heritage is being lost all the time," Dr Holdaway said.
"And you get people who want to make a buck out of it and they steal bones from cave systems.
"We know that - in the past at least - material has been spirited out the country against our laws, but quite legitimately taken into other countries."
Unlike Britain, South Africa and Australia, New Zealand has no law protecting paleobiological sites on private land.
"When the Antiquities Act was revised, natural sites were explicitly excluded.
"So unless it's on DOC land, it's the landowner who has jurisdiction - our national heritage belongs to landowners, and it's only by their good offices that scientists can access these sites."
Many sites were destroyed before scientists could examine them and others were pillaged for profit.
Some unscrupulous individuals were even going into caves on Department of Conservation land to harvest moa bones, Dr Holdaway said.