December 20, 2010 | 4
Penguins are perhaps the most popular birds on Earth, thanks in equal measure to their incredible life cycles and charming tuxedo-clad appearances. Among their long list of superlatives, penguins can survive sub-freezing temperatures and gale force winds, dive over 1600 feet deep, hold their breath for more than 15 minutes, and survive with no food for weeks by living off stored fat . These facts are so often repeated that they sometimes lose their initial wonder. Talking to K-12 schools as a guest speaker, I’ve found that half the classroom often knows many of these bits of penguin trivia before the presentation even starts, thanks to popular books, television specials, and the movie "March of the Penguins".
However, our knowledge of penguins extends beyond the present day menagerie of 19 species. Some of our greatest insights into these incredible birds come from the fossil record. Delving into the history of extinct species has completely changed the ways that paleontologists and biologists view penguins, often in surprising ways. Here are five things you probably didn’t know about penguins:
1. Penguins are Ancient Birds
Most people think of penguins as "modern" birds. We don’t often picture them alongside extinct animals such as mastodons, but penguins pre-date many of the best-known fossil mammals. In fact, the most ancient penguin fossils are amongst the oldest fossils discovered from any group of living birds. Waimanu ("Water Bird" in Maori) is the earliest known fossil penguin taxon. Two species of Waimanu are known: Waimanu manneringi and the slightly younger and smaller Waimanu tuatahi. Both species hail from the South Island of New Zealand. The oldest fossils of Waimanu manneringi are an astounding 61.6 million years old [2,3]. To put this in perspective, Waimanu lived only 4 million years after the dinosaurs and more than 50 million years before the earliest close relatives of modern humans.
Waimanu would have lived in a world much different than today’s. Climate was much warmer. Plate tectonic activity had not yet shifted the continents to their modern-day positions, so South America and Australia were still attached to Antarctica. Few large mammals roamed the landscape. Most importantly, ocean ecosystems were wide open in many ways. At the end of the Cretaceous Period (65.5 million years ago), the same mass extinction that wiped out the dinosaurs also killed off many marine reptiles such as mosasaurs and plesiosaurs, as well as decimating sharks. This created an opportunity for other groups of animals to return to the sea, and penguins were among the first to take it. In fact, Waimanu and other early penguins plied the oceans long before the first fully aquatic whales and pinnipeds (seals, sea lions and walruses) evolved.
Were we to travel back in time and see a group of Waimanu standing on the beaches of Proto-New Zealand, our initial thought would most likely be: "I think that’s a penguin". This is because Waimanu had many of the key features we consider to be characteristics of penguins, but was also different in many ways. To start, Waimanu was completely flightless. It also would have employed the endearing upright waddle that living penguins do when moving about on land, based on features of the leg bones and the necessity of balancing the heavy muscles that powered the flippers. These traits alone would probably trip our "penguin radar". On the other hand, the slender bones of the skull and flipper suggest a more graceful profile. Waimanu’s head and neck probably looked somewhat more like a those of a cormorant than a modern penguin. Furthermore, the wing bones do not yet show evidence of the locked joints that modern penguins have. This ancient penguin may have been able to fold its wing, something you will never see a living penguin due to its stiff board-like flippers.
So, Waimanu was a penguin in transition, still experimenting with a new skeletal plan for underwater "flight" and exploring a new niche left vacant by marine reptiles. A few million years later, these primitive penguins would give rise to a host of descendants of all shapes and sizes.
2. Giant Penguins Once Swam the Southern Oceans
Celebrated for its amazing polar march, the living Emperor Penguin reaches about 3 feet in height. This is a fairly impressive benchmark, given that most living penguins are comparatively pint-sized fellows standing in the neighborhood of two feet tall. Yet, there were once a flotilla of extinct species that would easily tower over the largest Emperor.
Largest of all is the enigmatic Pachydyptes ponderosus, known only from a few impressive flipper bones collected from a limestone in New Zealand almost one hundred years ago . During a research trip in 2006, I visited the Te Papa Tongarewa museum to study this magnificent specimen. Holding the main flipper bone of Pachydyptes in my hand was like holding a brick. The already solid and massive bone had become even more dense due to the processes of fossilization.
Pachydyptes was a true giant, but it is hard to reconstruct how big the species actually was because we only have a few pieces of the skeleton. It’s risky to just "scale up" from a living penguin because as we find more and more skeletons, we are also discovering that extinct penguin species had different body plans. Some were short and stout, while others were tall and slender.
Some of the most complete skeletons come from New Zealand and Peru [2,5], and these new finds suggest that the tallest penguins reached about 4 feet 6 inches standing on land, and about 5 feet long swimming through the water. The difference is due to the neck and beak, which stick straight out in the swimming animal and therefore add more to length than to standing height. Such penguins would surely intimidate any time traveling human explorer. Remember that penguins are bulky animals – they have very powerful "flight" muscles that allow them to propel themselves through water (which is ~800 times denser than air) and they also wrap themselves in a thick layer of blubber for insulation and to store energy. I’d take even odds on Pachydyptes being able to win a sumo wrestling contest with any penguin alive, and many humans at that. Below is a life reconstruction of an unnamed species of penguin from 27 million year old greensands from New Zealand, with an Emperor and a human silhouette for scale.
3. Penguins Did NOT Evolve in Cold Environments
When most people think about penguins, they think "cold." This is certainly reasonable, considering all of the advertisements portraying penguins as purveyors of ice-cold drinks and frozen treats. Television specials and movies like "March of the Penguins" also tend to focus on the penguin species that live in Antarctic environments because their life cycles are so fascinating. However, many of the penguin species alive today live outside the Antarctic Circle. A few even live in very hot environments, like the Humboldt Penguin, which breeds along coastal deserts, and the Galapagos Penguin, which actually lives on the Equator.
Some of my own research has focused on the evolutionary relationships of penguins. By determining where each species fits in the family tree, we can better understand how penguin evolution has been shaped by global changes such as the movement of the continents and climate change. We’ve already met Waimanu, the oldest penguin. This species is also the most basal (primitive) species in the penguin tree, which suggests that penguins got their start in New Zealand where the Waimanu fossils are found. Penguins don’t show up in Antarctica until later, and when they do the southern continent is still enjoying a warm phase with no permanent ice sheets.
Analyses of penguin bones and DNA suggest that the King and Emperor Penguins [6,7] are the most basal of the living species (the first to split off the modern part of the penguin evolutionary tree). Because both inhabit icy environments, we might naturally assume penguins originated in such places if we had only the living species distributions to guide us. However, when we start adding fossil penguins to the evolutionary tree a very different picture materializes [8,9]. During the Paleocene Epoch, the time interval when Waimanu appeared, climate was much warmer than today: average global sea temperature was about 6-8°C higher than today . The same is true of the Eocene Epoch, the time period when many of the giant penguins thrived. So, early penguins evolved and diversified long before polar ice caps formed. Their environments were more like those of the African Jackass Penguin, shown here enjoying a warm day at the beach, than the ice sheets favored by Emperors and Adélies.
Understanding that penguins evolved in a warm climate makes a big difference for how we study their evolution. We can’t explain all the interesting changes in the bones and feathers of penguins by saying they are related to surviving in glacial environments, because we know they first evolved during warmer times. This is a great example of how paleontology can shape the way biologists look at living animals.
4. Some Extinct Penguins were Spear-Fishers
Look closely at the skull pictured below and you still probably would not recognize it as a penguin. The beak is remarkably long, taking up 2/3rds of the skull and powerfully constructed by multiple bones fused into a single spear-like shape. At the tip, where normal penguins have a slight hook to snag prey, the beak in this penguin is straight and pointed. This is Icadyptes salasi, a spear-beaked penguin from Peru [5,11].
Icadyptes salasi was discovered in 34 million year old sediments from the ocean floor that were driven violently onto the continent by plate tectonic forces. This fossil was a major find, because skulls are very rare in the fossil record of most groups, and penguins are no exception. Over 5000 penguin bones of one type or another have been collected by paleontologists, but perhaps two dozen skulls are known and most are very badly preserved. As more and more penguin skulls are found, several more beaks have come to light and it appears that a very long beak was the standard for at least the larger species. In some of these other fossils, the beak is close to the length seen in Icadyptes, but the bones are less tightly fused together.
What could a penguin be doing with this bizarre beak? There may be some clues in other areas of the skeleton, such as the neck vertebrae. These bones show very strongly developed attachment sites for muscles, which would convey strength and perhaps resistance to the shock of impacts. Our best guess is that Icadyptes was spear-fishing, impaling large fish and squids with its powerful beak. It much have been an awe-inspiring predator, and not something you’d volunteer to swim with during an aquarium show.
5. Ancient Penguins Wore Coats of Red and Grey Feathers
Color usually remains unknown for extinct animals. In most cases, scales, fur and feathers are destroyed during the fossilization process, leaving only bones behind. Even when traces of soft parts like feathers are preserved, they often leave only a dark carbon film or some impressions. However, sometimes color leaves a microscopic fingerprint. This comes in the form of melanosomes, tiny pill-shaped components of cells that impart color to structures like bird feathers and mammal hair. Luckily for paleontologists, melanosomes are tough. They can survive for millions of years, outlasting many other biological substances. Paleontologists have discovered them in seemingly unlikely places, such as in the fossilized ink sac of an extinct squid .
One of the most surprising places melanosomes have been found is within a set of 36 million year old penguin feathers belonging to the species Inkayacu paracasensis . This species is very important because it is the only fossil penguin that preserves feathers and skin, an incredible rarity for marine fossils. Inkayacu paracasensis reveals that penguins evolved their specialized small, scaly, flattened feathers deep in the past. The melanosomes also reveal that the feathers had an unexpected hue.
One might have suspected evidence for a black and white coating of feathers in Inkayacu. After all, every living penguin except for the Little Blue follows essentially the same color scheme – black on top, white below. This is thought to useful in countershading penguins to help make it more difficult for predators or prey to detect them against the background. So, it is a complete surprise that the shapes of the fossil melanosomes matched those of modern reddish brown and grey feathers. This suggests Inkayacu had a radically different appearance than today’s tuxedoed penguins. Only a few years ago, no one would have suspected that melanosomes could be preserved in the fossil feathers, providing a great example of how new advances make new discoveries possible.
Ancient penguins have a fascinating story to tell us. Since 2005, ten new extinct penguin species have been discovered. Surely more are on the way. No one would have predicted spear-billed penguins with red feathers a few years ago, and the next round of discoveries are bound to include some more surprises.
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4. Oliver, W.R.B. 1930. New Zealand Birds. Fine Arts (N.Z.) Limited: Wellington. 541pgs.
5. Clarke, J. A., D. T. Ksepka, M. Stucchi, M. Urbina, N. Giannini, S. Bertelli, Y. Narváez, and C. A. Boyd. 2007. Paleogene equatorial penguins challenge the proposed relationship between biogeography, diversity, and Cenozoic climate change. Proceedings of the National Academy of Sciences 104:11545-11550.
6. Bertelli, S., and N. P. Giannini. 2005. A phylogeny of extant penguins (Aves: Sphenisciformes) combining morphology and mitochondrial sequences. Cladistics 21:209-239.
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8. Ksepka, D. T., S. Bertelli, and N. P. Giannini. 2006. The phylogeny of the living and fossil Sphenisciformes (penguins). Cladistics 22:412-441.
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10. Zachos, J., M. Pagani, L. Sloan, E. Thomas, and K. Billups. 2001. Trends, rhythms, and aberrations in global climate 65 Ma to present. Science 292:686.
11. Ksepka, D. T., J. A. Clarke, T. J. DeVries, and M. Urbina. 2008. Osteology of Icadyptes salasi, a giant penguin from the Eocene of Peru. Journal of Anatomy 213:131-147.
12. Doguzhaeva L., R. Mapes, H. Mutvei H. 2004. Occurrence of ink in Paleozoic and Mesozoic coleoids (Cephalopoda). Mitt. Geol.-Paläont. Inst. Univ. Hamburg 88:145-156.
13. Clarke, J. A., D. T. Ksepka, R. Salas-Gismondi, A. J. Altamirano, M. D. Shawkey, L. D’Alba, J. Vinther, T. J. DeVries, and P. Baby. 2010. Fossil evidence for evolution of the shape and color of penguin feathers. Science 330:954-957.
Figure 1: Composite skeleton image of Waimanu created by Tatsuro Ando and life reconstruction of Waimanu tuatahi (artwork by Chris Gaskin, ©Geology Museum, University of Otago). Used with permission; Figure 2: Photo of Pachydyptes and Adélie Penguin flipper bone side by side, by the author; Figure 3: Scaled reconstruction of a New Zealand giant penguin, with silhouettes of an Emperor Penguin and a human for scale. Fossil penguin artwork by Chris Gaskin, ©Geology Museum, University of Otago. Used with permission; Figure 4: Photo of Icadyptes salasi skull by the author; Figure 5: Photo of South African penguin colony by the author; Figure 6: Reconstruction of Inkayacu paracasensis by Katie Browne, ©Julia Clarke, University of Texas at Austin. Used with permission. Inset shows feathers and microscope image of melanosomes from .
About the Author: Dan Ksepka is a Research Assistant Professor of the Department of Marine, Earth, and Atmospheric Sciences at North Carolina State University and Research Associate of the Department of Paleontology at the North Carolina Museum of Natural Sciences. He has searched for fossil penguins in South America, Africa and New Zealand and also studies sauropod dinosaurs and choristoderan reptiles. He is @KsepkaLab on Twitter, and blogs at March of the Fossil Penguins.
The views expressed are those of the author and are not necessarily those of Scientific American.
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