Archive for March 2012
What was the world like when Kairuku penguins lived? It was quite different from today. Zealandia – a formal name for proto-New Zealand bore little resemblance to its modern day configuration. Sea level in the region was relatively higher, both because the main islands of Zealandia were not as uplifted as they are today and because there were no permanent polar ice sheets, leaving more water in the oceans instead of locked away as ice. Thus, shallow seas submerged large swathes of the South Island,where Kairuku fossils have been recovered. It was a great place to be a penguin. The small emergent parts of the South Island would have been safe breeding grounds, given the remoteness from other land masses and lack of terrestrial predators to disturb nests.
Fossil bones of Kairuku penguins are found in a rock formation called the Kokoamu Greensand. As the name implies, this formation is primarily composed of greenish sedimentary rock formed when seafloor sediments were compressed and became lithified. Several types of sediments are mixed in different layers, including fine quartz sand, calcareous sands, and clays. The sandstones are heavily bioturbated – that is, mixed up by the borrowings of animals. The seafloor was teaming with life, both on the surface and beneath. Some of the most common invertebrate fossils in the Kokoamu Greensand are shells of the brachiopod Waiparia. Brachiopods are shellfish that belong to a whole different class than the bivalve mollusks (clams, oysters, and relatives) that make up most modern shellfish faunas. Waiparia belong to the family Terebratellidae, which I remember fondly from my undergraduate paleontology labs for their spaceship-like shapes. These shellfish would have anchored themselves into the seafloor with a holdfast and used their filtering lophophores to collect food particles from the current. I’ve been told that brachiopods are a poor dietary choice, both in terms of nutrients provided and taste. More familiar and probably more delicious mollusks also lived in the region and are found as fossils in the Kokoamu Greensand. Scallops are fairly common, and sea snails and clams were present too.
Kairuku also had some rather unwelcome neighbors. Among these were many species of sharks, the grandest of which was Carcharodon angustidens. This species was a relative of the Great White Shark and reached about 9m (27 feet) in length. Such predators would have been dangerous even to fully grown Kairuku penguins. Another predatory group was the Squalodontia, an extinct family of shark-toothed dolphins. Unlike the conical teeth of living dolphins, squalodonts had serrated teeth, with multiple small cusps along the edges. Waipatiidae were another interesting fossil group of predatory dolphins. One of the amzing things about the species Waipatia maerewhenua is its procumbant incisors. These front teeth point forward from the snout, rather than pointing down like the teeth of a normal dolphin. You can see an artist reconstruction of a beached Waipatia maerewhenua in the background of the Kairuku waitaki artwork that accompanied our paper by scrolling down. This dolphin was not huge like Carcharodon angustidens, but was probably dangerous to at least juvenile Kairuku penguins as well as smaller contemporary penguin species like Duntroonornis parvus. You an read more about this amazing fossil dolphin and other New Zealand fossils at the University of Otago Geology Museum’s website.
A Humboldt Penguin known as “Penguin 337” has escaped from the Tokyo Sea Life Park. It may seem amazing that the bird scaled a 17 foot rock wall to make its getaway, but penguins are in fact exceptionally good climbers despite their stumpy feet. The penguin in question is a one-year old bird. It has since been spotted in the Old Edogawa River. Based on what we know about the species, there are high hopes the penguin will be recovered before it falls into harm’s way. Humboldt Penguins tend to stay relatively close to shore in the wild, so it is not too likely that the loose penguin will attempt an ocean crossing and get lost at sea. Wayward penguins often survive for long periods, and there are historical records of intentionally released penguins surviving for years in the Baltic and stowaways reaching Alaska. If Penguin 337 can steer clear of predators, it should find plenty to eat in the area and with luck will eventually be returned to the zoo by the search party. Check out this video that accompanies the story at MSNBC:
Today my interview with Bob McDonald on CBC’s Quirks and Quarks will air and be uploaded as a podcast. We cover some ground on penguin evolution and the Kairuku story.
Dr. Ewan Fordyce, discoverer of the Kairuku waitaki and Kairuku grebneffi holotypes and my co-author on the recent paper in Journal of Vertebrate Paleontology, has just added a new page with more details about the fossils and on general New Zealand Paleontology. There are additional pages on Waimanu penguins, fossil whales, sharks, reptiles and more.
Which species is the largest penguin ever to have lived? Well, there may be multiple answers to that question. Kairuku grebneffi breaks the record for the longest humerus (the main flipper bone). Measuring 176.6 mm, the humerus of this species narrowly beats the record of 175.8 mm held by Pachydyptes ponderosus since 1930. On the other hand, the humerus of Pachydyptes ponderosus is almost 50% wider than that of Kairuku grebneffi. This is really interesting, because it suggest that the enigmatic Pachydyptes ponderosus was a really stout penguin at the the opposite end of the spectrum from the slender Kairuku grebneffi. In terms of which species is largest, it is quite possible that Kairuku grebneffi was the tallest penguin species ever to have lived and Pachydyptes ponderosus was the heaviest. It’s note really possible to tell for sure at this point, because Pachydyptes ponderossus is known only from three bones. Maybe it had wide wings and long legs, maybe it had a stubby bill and a long tail. We won’t know how the rest of the penguin looked until we find more fossils. It’s also important to keep in mind that only a fraction of the species that have evolved over the billions of years of Earth history have made it into the fossil record, and only a fraction of these have been discovered. There may be an even bigger penguin lurking out just under the surface in the rocks of New Zealand, lying exposed in the remote deserts of Peru, or buried in a layer of ice in Antarctica.