Reconstruction of the giant parrot Heracles, dwarfing a bevy of 8-cm-high Kuiornis, small New Zealand wrens scuttling about on the forest floor. (Brian Choo/Flinders University)

Scientists have discovered the fossils of what may be the biggest parrot that ever lived — possibly as tall as a three-year-old child and weighing about twice as much as an average house cat.

Heracles inexpectatus, named after the strongman and hero Heracles of ancient Greek mythology, was estimated to be a metre tall and a hefty seven kilograms, based on fossil leg bones found in New Zealand, researchers reported this week in the journal Biology Letters .

That would make it about double the size of the previous biggest known parrot, the kakapo, a flightless species that still lives in New Zealand, but is critically endangered.

The researchers think Heracles inexpectatus probably couldn't fly either.

The giant parrot lived about 19 million years ago, during the early Miocene, a time when small three-toed horses roamed North America. Back then, its home in New Zealand was a subtropical forest full of laurels, palms and lots of other birds such as parrots, pigeons, eagles and the forerunners of the giant flightless moa, which stood up to 3.6 metres tall and were the biggest birds that ever lived.

Heracles "no doubt" had a "massive parrot beak that could crack wide open anything it fancied," Mike Archer, a researcher from the University of New South Wales Paleontology Research Centre and co-author of the paper, said in a statement.

He suggested its diet may have consisted of far more than nuts, fruits and seeds — "perhaps even other parrots."

The brown bones are the fossil leg bones of the giant parrot Heracles inexpectatus, which are compared to the white bones of the largest living parrot, the kakapo. The silhouettes compare the size of Heracles to a human. (Worthy et al.)

Heracles's bones were first unearthed for a site in Otago in 2008, but weren't re-examined again until earlier this year. Initially, the researchers told Agence-France Presse , they thought it was an eagle.

"New Zealand is well known for its giant birds," Trevor Worthy, a Flinders University professor and lead author of the paper, said in a statement. That included the moas, giant geese, giant adzebills and a giant eagle.

"But until now, no one has ever found an extinct giant parrot — anywhere."