Kairuku grebneffi

Kairuku grebneffi is an extinct species of giant penguin. It is among the tallest and heaviest penguins attested to, weighing 50% more than modern emperor penguins. The species is marked by a slender body and long, slender beak. K. grebneffi lived in what is now New Zealand during the late Oligocene, going extinct around 25 million years ago. The first bones of the species were discovered in 1977, but it was not classified as a distinct species until 2012.

Description

Kairuku grebneffi were nearly 1.5 metres (4.9 ft) long and stood 1.3 metres (4.3 ft) tall.^[1] Adult individuals weighed an estimated 60 kilograms (130 lb), 50% more than modern emperor penguins.^[2] K. grebneffi had the longest humerus bone of any penguin extant or attested to in the fossil record.^[1] The bird had a longer beak and more slender body than those of modern penguins.^[3] Relative to its body size, its flippers were longer and probably more flexible than those of modern species.^[3][4] It had short, thick legs, but overall looked a lot like a modern penguin "from a distance."^[3][4] K. grebneffi is distinguished from its sister species K. waitaki primarily on the basis of vertebrae spacing and by having a straight tipped beak, compared to the curved tip of K. waitaki.^[1] Additionally, all known specimens of K. grebneffi are larger, although small sample size prevents that from being a diagnostic characteristic.^[1]

K. grebneffi likely used its slender beak to spear fish and squids.^[3] It likely was able to dive deeper and swim farther than modern penguins.^[2] Predators of the bird likely included sharks and Squalodons.^[3]

K. grebneffi lived in what is now New Zealand late in the Oligocene period, roughly 25-27 million years ago.^[2] At the time, most the area was mostly ocean, with a few isolated islands.^[2] It is believed that these rock outcrops provided safe breeding grounds and easy access to rich food resources in the surrounding seas.^[2] K. grebneffi lived alongside at least four other penguin species. It is likely that each species fed on different kinds of fish.^[5]

K. grebneffi was among of the last of the giant penguins.^[3] The cause of K. grebneffi's extinction is unknown, but was probably related to "the drastic change in paleoenvironment" according to Tatsuro Ando, one of the scientists who classified the penguin.^[3] Other possibilities include the arrival of new predators and increased food competition.^[2]

Discovery

The first Kairuku bones were discovered in 1977 by Ewan Fordyce, although they were not identified as such at the time.^[2] In February 2012, an international team of scientists led by Fordyce and Daniel Ksepka reconstructed a K. grebneffi skeleton using a few "key specimens" from the Kokoamu Greensand of the North Otago and South Canterbury districts of New Zealand.^[1][2] The specimens used represent some of the most complete skeletons found of any extinct penguin, and thus provide valuable insight into the reconstruction of all extinct penguins.^[1] The king penguin was used as a guide during reconstruction.^[2]

K. grebneffi was named after Andrew Grebneff, a paleontologist from the University of Otago who died in 2010.^[1] The genus name Kairuku means "diver who returns with food" in Māori. The holotype was collected in 1991 from a drainage area of the Waipati stream, a tributary of the Maerewhenua River.^[1]

References