First Fossil Penguins from East Antarctica
Some new penguin bones have been discovered on the frozen continent of Antarctica. It may seem natural to think that most fossil penguins would come from Antarctica, given our fascination with the icy travels of species like the Emperor Penguin. However, there are few places paleontologists can look for fossils on the continent. Very few rocks are exposed for prospecting due to the overlying ice sheets. Up until now, all of the penguin fossils have come from West Antarctica. In fact, they have all been from Seymour Island, which is part of the archipelago of islands off the tip of the Antarctic Peninsula. Although these fossils include some amazing species, this geographical restriction has greatly limited our knowledge of the history of the southernmost penguins. The oldest reported bones are assigned to the species Crossvallia unienwillia from the late Paleocene (about 55 million years ago). We know there was a diverse group of species of all sizes, including some giants, thriving from about 50 million years ago to about 35 million years ago. Most of this interval in Earth history was quite warm, and the penguins were living in a fairly temperate environment complete with forests. Over the next 35 million years, climate cooled leading to the growth of ice sheets which eventually covered almost all of Antarctica.
What happened to the penguins? Did they adapt? Did they die out? If so, when did new species replace them? Today, several species of penguin breed in Antarctica including the Emperor Penguin, Adélie Penguin, Chinstrap Penguin, Gentoo Penguin, and Macaroni Penguin. We know that these modern species are distantly related to the original archaic penguin inhabitants of Antarctica. But, because of the big gap in the fossil record we are not sure when the new species first arrived and what happened in the meantime.
The new fossils were discovered at Prince Charles Mountains, which is in East Antarctica, almost directly opposite from the Seymour Island sites. Two flipper bones, a humerus and a radius, were found in a shell bank. This was a fortuitous place for the find, because shells can be dated with isotope methods. The scientists looked at the levels of a radioactive isotope of the element Strontium to figure out the age of a scallop found near the penguin bones. These tests indicate the fossils are 10.2 million years old, much younger than the previous fossil records from Seymour Island.
Features of the bones suggest they belong to the genus Spheniscus, the group of “tuxedo penguins”. That’s an interesting fact, because today Spheniscus penguins (including Galapagos and Black-footed Penguins) are some of the species most adapted to warm conditions. They make it south as far as Tierra del Fuego, but don’t cross over to Antarctica. Because things are already quite chilly in the south by 10 million years ago, it is a surprise to see a Spheniscus penguin in the region. I am very excited by the first announcement of bones, and hope more is in store. East Antarctica may well hold some important secrets of penguin evolution.
Jadwiszczak P., Krajewski K.P., Pushina Z., Tatur A. Zieliński G. 2012. The first record of fossil penguins from East Antarctica. Antarctic Science, FirstView Article, pp 1-12, DOI: http://dx.doi.org/10.1017/S0954102012000909; Published online: 15 November 2012.