Professor Fordyce worked with an international team to dust off and reconstruct fossilised bones, some of which were extracted from a cliff-face in Waimate, South Canterbury 35 years ago.
Two main kairuku fossils were used, one of which Professor Fordyce found "by chance" while searching for whale bone fossils as a post-graduate palaeontology student.
Using a king penguin as a model, the scientists reconstructed the kairuku's size and proportions.
The lead author for a paper on the bird, Dan Ksepka from North Carolina State University, said it was "an elegant bird by penguin standards, with a slender body and long flippers, but short, thick legs and feet".
"If we had done a reconstruction by extrapolating from the length of its flippers, it would have stood over six feet tall.
"In reality, kairuku was about 4ft 2in tall [1.27m] or so."
Researchers said most of New Zealand would have been under water at the time the bird existed, and the kairuku would have sheltered from predators on rocky outcrops.
It was believed to have been made extinct 24 to 25 million years ago, possibly because of increased predation or a change in climate.
Bigger penguins have been discovered: at least two extinct species found in Peru stood about 1.5m tall.
STANDING TALL
Kairuku - 1.27m
Emperor penguin - 1.0m-1.2m.
