An international team, including researchers from the University of Cambridge, reported the discovery in the Journal of Paleontology. The paper's senior author, Alan Tennyson from the Museum of New Zealand Te Papa Tongarewa, discovered the fossils in 57 million-year-old beach boulders in North Otago, on New Zealand's South Island, between 2016 and 2017.

The fossils were then exposed from within the boulders by Al Manning. They have been identified as being between 59.5 and 55.5 million years old, marking their existence as roughly five to 10 million years after the end-Cretaceous extinction which led to the extinction of non-avian dinosaurs.

The team used laser scanners to create digital models of the bones and compare them to other fossil species, flying diving birds like auks, and modern penguins. To estimate the size of the new species, the team measured hundreds of modern penguin bones and calculated a regression using flipper bone dimensions to predict weight.

They concluded that the largest flipper bones belong to a penguin that tipped the scales at an astounding 154 kg. In comparison, emperor penguins, the tallest and heaviest of all living penguins, typically weigh between 22 and 45 kg.