Scientists in New Zealand have uncovered fossilised bones from an extinct monster penguin that was about the size of a human and swam the oceans some 60 million years ago.

They say the previously undiscovered species is believed to have stood about 5ft 2in and weighed up to 80kg.

It is thought to have been one of several species of giant penguins that thrived soon after dinosaurs died out.

The findings were published this week in Alcheringa: An Australasian Journal Of Palaeontology.

Dr Paul Scofield, co-author and a senior curator at the Canterbury Museum, said the discovery is significant because the species is similar to another giant penguin found in Antarctica and helps connect the two regions during that era.

Dr Paul Scofield
Dr Paul Scofield holds the fossil, left, next to a similar bone in an emperor penguin (Mark Baker/AP)

He said that following the extinction of dinosaurs, marine reptiles and gigantic fish, it seemed there was an evolutionary opportunity for penguins to thrive and grow in size.

“The oceans were ripe for the picking with the lack of mega predators,” Dr Scofield said. “It looks like what was going on was that penguins were just starting to exploit that niche.”

But he said the giant penguins themselves became extinct within 30 million years as large marine mammals began ruling the waters.

The monster penguins, named Crossvallia waiparensis, would have been about twice the weight and 1ft taller than the largest type of penguins alive today, emperor penguins.

Dr Scofield said the leg bones also indicate the monster penguin’s feet may have played a bigger role in swimming than is the case with penguins today.

Giant parrot discovery
The discovery of Heracles inexpectatus, right, was revealed last week (Canterbury Museum/PA)

The monster penguin’s bones, from its legs and feet, were found by amateur enthusiast Leigh Love about 18 months ago in the Waipara River bed near the South Island city of Christchurch.

Mr Love said he spotted the fragments in an eroding bank.

“It wasn’t until I got the fossils home and did a little preparation that I realised I had something completely different than what had been found before,” he said.

It comes a week after scientists revealed the discovery of fossils up to 19 million years old of a giant parrot near St Bathans in Central Otago, New Zealand.

Standing up to one metre tall and with a massive beak, it is understood the parrot fed on other birds. Researchers called it Heracles inexpectatus to reflect its Herculean myth-like size and strength – and the unexpected nature of the discovery.