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Extinct genus of birds From Wikipedia, the free encyclopedia
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]
| Kairuku Temporal range: | |
|---|---|
| |
| 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 | |
| Species | |
| |
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]
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]
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 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]
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]
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]
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