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Giant penguin fossils reveal 'elegant' shape

The fossils are so complete, researchers were able to create a sketch of the bird that went extinct nearly 27 million years ago

A team of researchers from the United States, New Zealand and Japan have characterized two new species of giant penguins found in New Zealand.  The three skeletons are so complete, researchers say they’re able re-create images of the birds that went extinct approximately 27 million years ago.

“In the case of several species, they’re only known from a single bone,” Daniel Ksepka, study co-author and Avian Paleontologist at North Carolina State University told “Having an entire skeleton together really lets you understand the overall appearance of the animal.”

“By far, these are some of the very best skeletons anywhere on earth,” he added.

From the skeletons, researchers found the giant penguins are a little more than four feet tall at 1.3 metres – about an entire ruler length taller than an emperor penguins – and look like they’ve been stretched out.

“They’re very elegant penguins,” Ksepka said.  “If you look at the skeleton, the bones that make up the trunk – the chest area, including the sternum and other bones – they’re quite elongated.  The same thing is true about the flippers.”

“The legs are short like normal penguins, but quite powerfully built and the beak’s long, narrow and very straight,” Ksepka added. Both species of giant penguin belong to the genus Kairuku, a side-branch of penguins called stem penguins. 

They’re part of the evolutionary history of penguins, but separated from the main branch and went extinct approximately 27 million years ago during the late Oligocene period.

“They’re like an evolutionary experiment that ultimately failed,” Ksepka said.

The first of three skeletons was actually unearthed in New Zealand by R.  Ewan Fordyce, a Paleobiologist at the University Otago – who’s also a co-author – in 1977.   In 2011, Kspeka and Fordyce unearthed another giant penguin fossil in the same area, known as the kokoamu greensands.

The area’s a hot bed for penguin diversity today and was then too.   At the time, researchers say New Zealand was largely covered by water.  As water levels receded, shallow pools dried up, exposing skeletons of animals that lay preserved by the sand and silt after they died.  

“A lot of the area that’s farms, towns and forests was completely underwater and this was a great place for a penguin fossil to be deposited,” Ksepka said.  “It’s almost like walking on an ancient sea floor.”

The species differ from each other in several fine details.  When comparing beaks, for example, Kairuku waitaki’s bends at the tip whereas the other, Kairuki grebneffj, has a beak that’s straight to the tip.

“There’s differences in the knee joint – it’s quite wide in one of the penguins and narrow in the other,” Ksepka said. “If we look at the bones in the flipper we also see slight proportional differences and this is what we see in two different species that belong to the same genus.”

Why the giant penguins went extinct isn’t clear, researchers say.  Some have linked their extinction to climate change, while others have linked it to increased competition for food or nesting areas by other similarly sized animals like sea lions and dolphins.

“It’s something that’s not resolved and something we’re all very interested in,” Ksepka said. 

The genus names are derived from local Maori words for food and dive – kai and ruku.  The species K. waitaki’s named after a river in the region. 

The other species, K. grebneffi is named after New Zealand Paleontologist, Andrew Grebneff.  He prepared fossil’s for more than 25 years in Fordyce’s New Zealand lab before he died in 2010.

The research was published in the latest issue of the Journal of Vertebrate Paleontology

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