While searching through the beachy boulders of New Zealand's South Island, a crew of international scientists stumbled on an exquisite find: fossilized evidence of two new penguin species that roamed (or waddled) Earth more than 50 million years ago. 

But most importantly, one of the discovered penguins, dubbed Kumimanu fordycei, is probably the largest ever to have lived. A co-author of a study on the discovery, published Wednesday in the Journal of Paleontology, had a rather compelling way of putting it.

"At approximately 350 pounds, it would have weighed more than [basketball player] Shaquille O'Neal at the peak of his dominance!" Cambridge University's Daniel Field said in a statement. For comparison, emperor penguins, aka the largest penguins now living, weigh in at a maximum of 100 pounds (45 kilograms), according to a release. And a male ostrich, the largest bird now alive, can weigh up to about 290 pounds.

In terms of the height of this ancient (and perhaps slam-dunking) penguin, the first author of the study, Daniel Ksepka of Connecticut's Bruce Museum, tweeted out an image of what he calls the team's "best guess." It looks to be about the size of a human (if not bigger), but thankfully it seems much smaller than the monstrous penguin predicted to inhabit Earth post-humanity by paleontologist Dougal Dixon in 1981. Dixon imagined a 12 meter (nearly 40 foot) behemoth. Yikes.

The other species, named Petradyptes stonehousei, constituted five of the nine revealed specimens, yet was likely only slightly larger than a modern emperor penguin, the team said. It weighed in at about 110 pounds (50 kilograms). 

Together, the two novel species have confirmed for scientists that penguins got really big in their early evolutionary history, and the discovery sheds light on how these flightless birds' flippers changed over time. 

"Fossils provide us with evidence of the history of life, and sometimes that evidence is truly surprising," Field said. "Many early fossil penguins attained enormous sizes, easily dwarfing the largest penguins alive today."

Zeroing in on an iconic penguin trait, flippers, the team used techniques like laser scanning and environmental analysis to estimate various aspects of the two extreme species. 

First off, the team used laser scanners to create digital models of the bones and compare them to other fossil species such as the emperor penguin. That's how the researchers started extrapolating how big the prehistoric birds probably were. But some information was also gleaned by checking out the boulders within which all the specimens -- flipper bones and muscle attachment points -- were found to begin with. 

The rocks themselves were identified as being about 57 million years old, and the fossil species are thought to have lived between 59.5 million and 55.5 million years ago. 

This timeline falls within the late Paleocene era, and more specifically, it's roughly 5 million to 10 million years after the end-Cretaceous extinction, when the asteroid Chicxulub wiped out the dinosaurs. In a way, this means the giant penguin might've had more peace than you'd expect for an ancient animal -- unperturbed on a more-or-less dino-free Earth.

"Kumimanu fordycei would have been an utterly astonishing sight on the beaches of New Zealand 57 million years ago, and the combination of its sheer size and the incomplete nature of its fossil remains makes it one of the most intriguing fossil birds ever found," Field said.

And if you're wondering whether the lifestyle of a massive penguin differs from the daily rituals of cute little penguins we're used to, the answer is probably yes. 

For example, the researchers explain, a bigger penguin could capture larger prey, be better at conserving body temperature in cold waters, and could maybe migrate across the globe and set up residences beyond their hometown. 

A lot of ancient animals seem to have been significantly bigger than their modern-day ancestors, such as the dinosaurs, wooly mammoths and even this dog-size scorpion. Some experts hypothesize this is because of environmental factors like higher oxygen content in the air. Others believe it might've been because of efficient food uptake, as the penguin discovery team hints at. 

"Large, warm-blooded marine animals living today can dive to great depths. This raises questions about whether Kumimanu fordycei had an ecology that penguins today don't have, by being able to reach deeper waters and find food that isn't accessible to living penguins," Daniel Thomas of Massey University and study co-author said in a statement.

The newly unearthed giant species dubbed Kumimanu fordycei was named in honor of Ewan Fordyce, a professor emeritus at the University of Otago in New Zealand. "Without Ewan's field programme, we wouldn't even know that many iconic fossil species existed, so it is only right he have his own penguin namesake," Ksepka said in a statement.

The smaller find, Petradyptes stonehousei, has a much more literal name. It's derived from the Greek words "petra" for rock and "dyptes" for diver. Stonehousi, though, honors the late Bernard Stonehouse, whom the release calls the first person to observe the full breeding cycle of the emperor penguin.