PROFILBARU.COM

Kairuku; Temporal range: late Oligocene PreꞒ Ꞓ O S D C P T J K Pg N ↓
	Artist's impression of Kairuku
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Aves
Order:	Sphenisciformes
Genus:	†Kairuku; Ksepka, Fordyce, Ando & Jones, 2012
Type species
	Kairuku waitaki; Ksepka, Fordyce, Ando & Jones, 2012
Species
	K. grebneffi Ksepka, Fordyce, Ando & Jones, 2012; Kairuku waitaki Ksepka, Fordyce, Ando & Jones, 2012; Kairuku waewaeroa Giovanardi, Ksepka & Thomas, 2021;

Kairuku is an extinct genus of penguin.^[1] It contains three species, K. grebneffi, K. waitaki ^[2] and K. waewaeroa.^[3] This taxon is known from bones from 27 MYA (late Oligocene), from the Kokoamu Greensand Formation of New Zealand.^[1] It was historically referred to as Palaeeudyptes.^[1]

Etymology

The genus name Kairuku comes from the Māori words kai (“food”) and ruku (“to dive”).^[1]

The species name waewaeroa is from Māori waewae - "legs", and roa - "long", referring to the elongated hind limbs.^[3]

K. grebneffi was named after Andrew Grebneff, a paleontologist from the University of Otago who died in 2010.^[4]

Distribution

The fossils of Kairuku waewaeroa were found within the Glen Massey formation (34.6–27.3 Ma) in the North Island of New Zealand.^[3]

Description

Kairuku is one of the most completely known genus of Paleogene penguins. Described species are larger than modern emperor penguin which stood around a meter,^[1] K. grebneffi stood 1.28 metres (4.2 ft) tall,^[1] and K. waewaeroa is even larger with height up to 1.38 metres (4.5 ft).^[3] Unnamed species called Glen Murray fossil penguin is estimated to have a height 2 to 20% taller than K. grebneffi.^[5]

Kairuku grebneffi

Kairuku grebneffi were nearly 1.5 metres (4.9 ft) long and stood 1.3 metres (4.3 ft) tall.^[4] Adult individuals weighed an estimated 60 kilograms (130 lb), 50% more than modern emperor penguins.^[6] K. grebneffi had the longest humerus bone of any penguin extant or attested to in the fossil record.^[4] The bird had a longer bill and more slender body compared to living penguins.^[7] Relative to its body size, its flippers were longer and probably more flexible than those of extant species.^[7]^[8] The bird had short, thick legs, but overall, looked much like a modern penguin "from a distance."^[7]^[8] K. grebneffi is distinguished from its sister species K. waitaki primarily on the basis of vertebrae spacing and by having a straight tipped bill, compared to the curved tip of K. waitaki.^[4] Additionally, all known specimens of K. grebneffi are larger, although small sample size prevents that from being a diagnostic characteristic.^[4]

K. grebneffi likely used its slender beak to spear fish and squid.^[7] It likely was able to dive deeper and swim farther than living penguins.^[6] Predators of the bird likely included sharks and Squalodons.^[7]

K. grebneffi lived in what is now New Zealand late in the Oligocene period, roughly 25–27 million years ago.^[6] At the time, most of the area was ocean, with a few isolated islands.^[6] It is believed that these rock outcrops provided safe breeding grounds and easy access to rich food resources in the surrounding seas.^[6] K. grebneffi lived alongside at least four other penguin species. It is likely that each species fed on different kinds of fish.^[9]

K. grebneffi was among of the last of the giant penguins.^[7] 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.^[7] Other possibilities include the arrival of new predators and increased food competition.^[6]

Kairuku waewaeroa

The skeleton of the holotype is one of the most complete skeletons of giant penguins that have ever been found. Phylogenetic analysis reveals a clade that unites^{[clarification needed]} New Zealand endemics Kairuku waewaeroa, Kairuku waitaki and Kairuku grebneffi. The probable height of K. waewaeroa is 1.38 m (4.5 ft), and the length of the body from the fingertips to the tip of the beak is 1.6 m (5.2 ft).^[3]^[10]

Discovery

The first Kairuku bones were discovered in 1977 by Ewan Fordyce, although they were not identified as such at the time.^[6]^[11] 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.^[4]^[6] 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.^[4] The king penguin was used as a guide during reconstruction.^[6]

The holotype of K. grebneffi was collected in 1991 from a drainage area of the Waipati stream, a tributary of the Maerewhenua River.^[4]

Fossil remains of Kairuku waewaeroa, or Kawhia giant penguin, fossil remains were found in Kawhia Harbour on the North Island of New Zealand.^[3]^[12]