At an estimated 15 pounds, the extinct was nearly double the weight of the endangered Kakapo.

A collection of bird bones sat idly in lab storage for more than a decade, believed to be the remains of an ancient eagle. Little did scientists know what was hiding in the fossils - a "Squawkzilla."

Labeled Heracles inexpectatus, the bird was discovered by scientists in New Zealand, according to a new study published Wednesday. At about 3 feet, the massive bird would likely have stood nearly as tall as the average American 4-year-old.

Scientists have been finding enormous prehistoric birds for years, but this one still managed to shock them. It's the largest parrot ever found, and it might have preyed on other birds.

At an estimated 15 pounds, the extinct was nearly double the weight of the endangered Kakapo, the largest living parrot.

The scientists approximated its immensity based on two leg bones, called tibiotarsi, under the assumption that they likely both came from the same bird. The researchers compared the drumsticklike bones to bird skeletons in the South Australian Museum collection and the Smithsonian National Museum of Natural History's electronic collection.

The fossils were dug up in 2008 in St. Bathans, New Zealand, where many thousands of bird bones have been found.

The Heracles bones were believed to be from an ancient eagle, but during a research project in the lab of Flinders University paleontologist Trevor Worthy, a graduate student rediscovered the bones. After that, a team of researchers began reanalyzing the findings this year, according to the BBC.

"It was completely unexpected and quite novel," Worthy, the study's lead author, told National Geographic. "Once I had convinced myself it was a parrot, then I obviously had to convince the world."

The bird likely lived during the Early Miocene, which spanned from about 23 million to 16 million years ago.

Researchers concluded the bird probably couldn't fly and consumed what was along the ground and easy to reach, according to National Geographic. But that might not have been enough to satiate the giant parrot.

It's possible the bird had more carnivorous ways like another New Zealand parrot, the Kea, which has been known to attack and subsequently munch upon living sheep, E magazine reported.

Michael Archer, a co-author of the research and paleontologist at the University of New South Wales, told National Geographic that Heracles might have even been eating other parrots, giving way to a nickname: "Squawkzilla."

Archer told AFP that the bird had "a massive parrot beak that could crack wide open anything it fancied."

Heracles likely won't be the final unforeseen fossil from the St. Bathans area, Worthy told AFP. The researchers have turned up many surprising birds and animals over the years.

"No doubt there are many more unexpected species yet to be discovered in this most interesting deposit," Worthy said.