The species Crossvallia waiparensis was 1.60 metres (5 feet and 3 inches) tall - the approximate size of an average human - weighed up to 80 kg and was 40 centimetre taller than present-day Emperor penguins, New Zealand's Canterbury Museum said in a statement.
"When the Crossvallia species were alive, New Zealand and Antarctica were very different from today - Antarctica was covered in forest and both had much warmer climates," said the museum's senior natural history curator, Dr Paul Scofield, underlining the close connection between the Oceanic archipelago and the ice-covered continent.
The "monster" penguin's fossilized remains were found in 2018 by an amateur paleontologist in North Canterbury, in the northeast of South Island, Efe news reported.
Museum curators studied the bones and concluded that they belonged to a species that had never been identified before.
The huge bird roamed New Zealand's coast during the Paleocene epoch of the Cenozoic Era, shortly after the Cretaceous-Tertiary (K-T) extinction event that saw the planet's erstwhile overlords - the dinosaurs and many related giant reptiles - vanish from existence, giving way to the age of mammals and birds.
The site of the discovery, known as the Waipara Greensand, is considered one of the world's most significant sites for prehistoric penguin fossils. Crossvallia waiparensis is the fifth ancient penguin species described from fossils uncovered there.
"The fossils discovered there have made our understanding of penguin evolution a whole lot clearer," said Dr Gerald Mayr of the Canterbury Museum.
( With inputs from IANS )