New Zealand today is home to a number of physically impressive parrots. Kakapos, the heaviest psittacines alive, are too chubby to fly. Sharp-beaked keas are strong enough to attack sheep and yank rubber parts off cars.
Once upon a time, though, there was a prehistoric Polly in New Zealand who had them all beat. This bruiser of a bird — whose discovery was announced Wednesday in Biology Letters — was perhaps three feet tall. At about 15.4 pounds, it was as heavy as some bowling balls, and twice as massive as the kakapo, which had previously held the record. That’s a lot of crackers.
“To have a parrot that big is surprising,” said Trevor Worthy, a vertebrate paleontologist at Flinders University in Adelaide, Australia and the paper’s lead author. “This thing was way outside of expectations.”
The parrot’s bones were found at the St Bathans Fauna, a fossil site on New Zealand’s South Island filled with creatures from the early Miocene, a period that spanned 19 to 16 million years ago.
In the 20 years paleontologists have been working there, the site “has filled an enormous gap” in the fossil record of a country known for its biodiversity, said Suzanne Hand, a professor at the University of New South Wales in Sydney and another author on the paper. Researchers at the St Bathans site have uncovered early records of some of the island nation’s most iconic animals, including the kiwi. They have also found previously unknown ancient species, including a large burrowing bat.
While their press office nicknamed the latest discovery squawkzilla, the researchers gave it the scientific name Heracles inexpectatus: Heracles after the strongman of Greek mythology, and “inexpectatus” because discovering it caught them off guard.
The bird’s large size actually delayed its discovery. When a team of paleontologists first found the parrot’s bones back in 2008 — a pair of the same bones you’d find inside a chicken drumstick, named tibiotarsi — they figured they had come from a bird of prey. So they “went into the eagle pile,” said Dr. Hand.
Earlier this year, Ellen Mather, a graduate student doing a project on eagles, determined the bones had been mischaracterized, prompting Dr. Worthy to take a closer look.
Identifying bird types based on bones involves analyzing “all of the little lumps and bumps that mark the insertions of ligaments and muscles,” Dr. Worthy said. On further inspection, the two leg bones featured an arrangement “only found in parrots.”
The bones provide a few more clues about the bird’s life.
Structurally, they are “quite solid and heavy,” said Dr. Worthy, suggesting that Heracles was most likely flightless, and subsisted on seeds and fruit from the forest floor. The tibiotarsus bones are also quite similar to the kakapo’s leg bones, which suggests a posture similar to the kakapo’s, but on a larger scale.
“Estimating body mass from individual bones is notoriously challenging,” said Armita Manafzadeh, a doctoral student at Brown University who was not involved in the study. “But there’s still no questioning that this parrot was absolutely huge.”
The researchers think the parrot evolved this way because of a phenomenon known as autapomorphic giantism, in which a member of an otherwise moderately sized group becomes humongous by taking over an empty ecological niche.
Although this often occurs on islands, it is different from a similar phenomenon, island gigantism, in which small, existing creatures become slightly bigger after they leave the mainland. Other prehistoric examples of autapomorphic giantism include the extinct mega-ducks of Hawaii, as well as the dodo, which was essentially an enormous pigeon, said Dr. Worthy. This is the first example of a parrot following this pattern.
The team is returning to St Bathans this year. Although they hope to find more Heracles bones, “we can’t go and plan to dig up a giant parrot,” Dr. Worthy said.
But the bird that surprised them once could certainly do so again: “If we turn over a lump of dirt and find one, we’ll be very pleased.”