An ancient giant penguin species has been discovered to have been living on the Chatham Islands.

The ancient penguin species, Kupoupou stilwelli, shared the seas with other ancient penguin species recently discovered on the South Island's east coast.

Kupoupou had human-sized cousins, including the recently described "monster penguin", the Crossvallia waiparensis, with the species standing at about 1.1 metre tall.

Kupoupou fills a gap between ancient and modern penguins, University of Canterbury alumnus Jacob Blokland said.

READ MORE:

* Monster penguin fossils found in North Canterbury

* Hoiho, the yellow-eyed penguin, wins bird of the year

* Wildlife provides pleasure, and pain, on the West Coast

* Concerns for penguins after diesel spill

"The shortened hind limb bone of Kupoupou approaches the form of many more recent, similarly sized penguins," he said.

"Its shorter legs were probably used in a different way than some other early penguins, and gave it a competitive advantage in the water."

SUPPLIED Artist's impression of Kupoupou stilwelli by Jacob Blokland.

The Kupoupou would have lived on the Chatham Islands between 62.5 and 60 million years ago.

The discovery appears in a paper from Blokland published in United States palaeontology journal Palaentologica Electronica this week.

"The fact that we've now found so many penguin species in and around the South Island's east coast suggests this area played an important role in the development of penguins," Blokland said.

"It might even be where they originated."

Blokland's research was supervised by Canterbury Museum Senior Curator Natural History Professor Paul Scofield.

Flinders University/SUPPLIED Jacob Blokland pictured with fossils in the Flinders University laboratory.

Scofield said Blokland's paper provided further support for the theory that penguins rapidly evolved shortly after the period when dinosaurs still walked the land and giant marine reptiles swam in the sea.

"We think it's likely that the ancestors of penguins diverged from the lineage leading to their closest living relatives such as albatross and petrels."

Many different species sprang up after the dinosaurs were wiped out, Scofield said.

"It's not impossible that penguins lost the ability to fly and gained the ability to swim after the extinction event of 66 million years ago, implying the birds underwent huge changes in a very short time.

"If we ever find a penguin fossil from the Cretaceous period, we'll know for sure."

Blokland has described the new species based on the fossilised bones of five partial skeletons.

SUPPLIED The Crossvallia waiparensis, about 1.6 metres tall, was identified from fossils found in Waipara, North Canterbury.

Another two specimens showed a second, larger penguin species was also present on the Chatham Islands, but there was not enough material to formally name it.

All the described skeletons were found on the Chatham Islands between 2006 and 2011.

The name Kupoupou is derived from the native language of the Chatham Islands' indigenous Moriori people, Te Re Moriori, and means "diving bird".

The Kupoupou is one of only a handful of animals with a Te Re Moriori scientific name.

The "monster penguin" Crossvallia waiparensis was identified from fossils found in North Canterbury and announced in August.

Evidence of the giant bird, which stood about 1.6 metres tall and weighed up to 80 kilograms, was discovered in Waipara by amateur palaeontologist Leigh Love in 2018.