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A while back, I posted a video of penguins chasing a butterfly. Apparently, this was not a one time occurrence. Here is another video of a similar incident caught on film. Besides being just plain fun, this video shows (A) why we call the main chasing species “Rockhopper Penguins” and (B) how big King Penguins are compared to most other species.
Penguins as a total group are old. Waimanu manneringi is approximately 61 million years in age, placing the origin of flightless diving penguins close to the Cretaceous-Paleogene (often called the K-T) boundary. However, “modern” or crown clade penguins have a much more shallow fossil record. In fact, the oldest fossil penguins that fall within the modern radiation (or, to put it scientifically, share the most recent common ancestor of the 18 living species) are only about 10 million years in age. However, because we do not have fossil for every modern penguin lineage, it has been unclear how long ago modern penguins appeared. It is possible they have been around for much longer than 10 million years, but we have missed the evidence because rocks of the appropriate type and age are either inaccessible or non-existent from many key regions like Antarctica.
A new study attempts to get around this limitation by combining fossil ages and DNA sequences. A team led by Dr. Sankar Subramanian conducted a “molecular clock”, or divergence dating analysis. This essentially means that they set the age of certain branching events to a range of times based on the age of fossils from well-represented types of penguins, like the Spheniscus lineage which has lots of cool fossils. With these fossil ages as calibration points, the ages for branching events in the penguin tree where fossil representation is poor can be estimated based on the amount of DNA divergence observed in the living species. Using this method, the age estimate for the origin of modern penguins is roughly 20 million years ago. This is cool, because it reinforces a paleobiological pattern that has been getting stronger and stronger as more fossils are recovered: modern penguins replaced archaic species in the not-so-distant past.
One of the strengths of this study is that the team took advantage of the fossil record of penguins to help date the tree. Besides the dates, an interesting finding is that tree groups together the two most ice-loving genera, Aptenodytes (King and Emperor Penguins) with Pygoscelis (stiff-tailed penguins). This result has actually been supported by morphological data in the past, but has not been supported by previous molecular datasets.
Dig is a great archeology and paleontology magazine targeted at 5th-9th graders. The November / December issue is all about fossil penguins, and I had a great time writing a few sections and editing for this one. Inside, you will also see interesting articles by Jessica Bramlet-Alves, James Proffitt, Sharon Robinson, Michelle Sclafani, Alyssa Stubbs, and Daniel Thomas. We cover everything from penguin beaks to mysterious Antarctic moss.
Interested readers can find copies here.
In another of the IPC fossil talks, Dr. Piotr Jadwiszczak described new fossil foot bones from Antarctic penguins. Even though Dr. Jadwiszczak showed details of the bones at his IPC talk, I thought it was best to wait for the paper describing these fossils to be released before writing about it, to avoid spilling the results too soon.
The fossils in question are new examples of the tarsometatasus that preserve strange features in the first toe region. Modern penguins have four toes. The second, third, and fourth toes are large and weight-supporting. The first toe, also known as the hallux, is very small. It consists of three bones – a metatarsal which connects to the tarsometatarsus (the main bone of the foot) and two phalanges, or toe segments, the second of which bears a tiny claw. These bones are almost never found in fossil penguins because they are small and thus easily swept away by currents or overlooked in the rocks. We have thus assumed that penguins have always had a tiny first toe, which is also consistent with the small size of this toe in their close living relatives, the petrels and albatrosses.
The new fossils complicate this picture. Several of them preserve a very well-developed scar for the ligament that attaches the first toe to the foot. This suggests the first toe may have been much larger in some early penguins. Interestingly enough, another specimen suggests even more variation. This bone (pictured below) suggests that the metatarsal may have been coalesced (basically absorbed) into the tarsometatarsus, perhaps leaving no external trace of a first toe at all. Fully understanding what was going on with these early penguins is going to require fossils that preserve the whole foot – another reason to keep excavating in Antarctica.
Reference: P. Jadwiszczak and A. Gaździcki. In press (published online 2013). Short Note: First report on hind-toe development in Eocene Antarctic penguins. Antarctic Science.
Penguins rarely make it to altitudes more than a few feet above sea level. In an interesting case reported at the International Penguin Conference, Dr. Carolina Acosta Hospitaleche presented a talk on penguin fossils from Cerro Plataforma in the Patagonian Cordillera. No, these were not mountain climbing penguins exploring treacherous passes. These fossils were transported upward long after their demise roughly fifteen million years ago. Along with the penguin bones fossilized seashells and shark teeth were also discovered, clear indicators that the bones were deposited in an oceanic environment.
Cerro Plataforma is an unexpected place to find penguins, because it is nearly a mile about sea level today. The fact that marine fossils have been lifted so spectacularly skyward from their original resting place on the seafloor speaks to the tremendous geological forces responsible for building the Andes – a process that still continues today and periodically manifests itself in severe earthquakes. These particular bones appear to have belonged to Palaeospheniscus bergi, one member of a radiation of penguins that thrived in South America during the Miocene but ultimately died out. The penguins may be a clue to the mystery of where the Cerro Plataforma marine rocks actually came from. There is some debate over whether they formed in the Atlantic or Pacific, a seemingly simply question that is obfuscated by the jumbling of the rocks under tectonic forces. It is interesting to note that regardless of whether the Cerro Plataforma rocks turn out to have been formed in the Pacific Ocean or the Atlantic Ocean, Palaeospheniscus penguins have been found all the way from Argentina to Peru. This indicates they not only lived in both oceans, but that their range stretched over a huge range of latitude, from near the Equator presumably down close to the tip of Tierra del Fuego. Thus these penguins achieved a pattern of distribution like that of Spheniscus penguins today, wrapping around almost all of the habitable areas of South America. It is likely they made it out onto nearby islands as well, but so far we have almost no fossils from offshore localities to verify this.
Acosta-Hospitaleche, C. and M. Griffin. 2013. Middle Cenozoic penguin remains from the Patagonian Cordillera. 8th International Penguin Conference Abstracts: 31.
Peru has yielded some amazing penguin fossils. In the deep past, over 30 million years ago, we have evidence of such wonders as the spear-beaked Icadyptes salasi and the feathered penguin “mummy” Inkayacu paracasensis. Closer to the present, roughly eleven million years ago, we start to see the first records of modern penguin genera turn up, sometimes as spectacularly well-preserved fossils. During the paleontology section of the International Penguin Conference, we heard about exciting new Spheniscus specimens from Martín Chávez, a PhD student at the University of Bristol.
The penguin genus Spheniscus includes four living species, which are the most warm-weather tolerant of the living penguins. Fossil evidence suggests this group of penguins first evolved in coastal South America, later spreading across the Atlantic to South Africa and across the Pacific to the Galápagos Islands. Fossils from Peru reveal the earliest glimpses of this lineage. Spheniscus muizoni is the oldest crown clade, or modern-type, penguin known at 11-13 million years in age.
Martín Chávez presented a study of several new specimens representing multiple extinct Spheniscus species. Two of the most impressive extinct Spheniscus species are the “bobble-headed” penguins Spheniscus urbinai and Spheniscus megaramphus. For many years, we have known that Spheniscus urbinai was a “tough” penguin with a robust postcranial skeleton. However, Spheniscus megaramphus has been known formally only from the holotype skull for the past decade. Nearly complete skeletons have recently come to light – Martín showed in his presentation that this species was even bigger and more powerfully built than Spheniscus urbinai He also showed off some excellent artwork in the form of skeletal reconstructions of these penguins. Side by side with a modern penguin, the differences really stand out. These penguins were larger and armed with more heavily constructed beaks than any modern species of Spheniscus, and surely took bigger prey than the anchovies preferred by the Humboldt Penguins that frequent Peruvian coastlines today. Closer examination of skulls from Peru even suggests there may have been multiple “megaramphus-type” species. So the picture of penguin diversity in the last few million years continues to improve.
Chávez Hoffmeister, M.F. 2013. The Peruvian Neogene penguins. Abstracts of the 8th International Penguin Conference: 32.
Chávez Hoffmeister, M.F. 2013. A review of the Peruvian Neogene penguins. PalAss Newsletter 81: 62-66.
I’ve just returned from the 8th International Penguin Conference and there were many excellent presentations on all manner of penguin research projects. It would be impossible to write about them all, but I will try to post a few samples of what the global community of penguin researchers has been up to lately. There are several great fossil projects that I will have to keep quite about for a few weeks or months until the “official” news is broken by the researchers involved in the form of papers, but you can rest assured that this winter should bring lots of new paleontology announcements.
First, to the presentation that most astounded me. The John Downer Productions team created a set of highly realistic robotic penguins to spy on living birds for a recent BBC documentary. Some penguins are timid around humans, and may flee when a normal camera team approaches. So, these robots allow scientists and filmmakers to get up close with the colony and capture intimate details of day to day life in a penguin colony. The robots are more than simple camcorders. Image recognition software allows them to do some amazing things, including remembering the identities of individual penguins based on their patterns of spots. This is incredibly useful to researchers who want to keep tabs on interactions between mates and other colony members.
Two of the robot penguins visited the conference and put on a demonstration that included successfully guessing the gender and age (within about 10 years) of an audience member. The robots also estimated “happiness” and “anger” levels of audience members based on smiles and scowls. Besides being great observation instruments, the robots are tough and sneaky. They can get blown over and right themselves, fall off a ledge without breaking, and even carry “egg-cams” to drop off at strategic locations. I was one of many who had their pictures taken with the Emperor robot.
Here is the trailer for the BBC special Spy in the Huddle:
This week marks the start of the 8th International Penguin Conference in Bristol. On Wednesday morning, I will be giving the keynote talk in a series of presentations about fossil penguin research. This will be a great opportunity to meet some paleontologists from Europe and South America, as well as worldwide experts on living penguin biology. There is sure to be some exciting new finds profiled at the conference, so stay tuned for reporting.
One of the patterns that stands out to me in the broad view of penguin evolution is that their skeletal adaptations seem to have proceeded from the ground up. By this I mean that even the earliest penguins that show up in the fossil record have very short, stout feet. Over the course of penguin evolutionary history, wing bones later continues to flatten towards the perfect flipper shape, the shoulder girdle reorganizes itself to accommodate more powerful upstroke muscles for diving, and finally cranial changes related to modified feeding preference show up. In a simplified sense, the skeletal changes proceed toe to head, rather than head to toe. So why the short legs? Hind limb morphology would seem to be an afterthought for a flightless diving bird. In fact, reducing the length hind limb is advantageous for many reasons, including cutting down on drag while swimming. Penguins can also use their short broad feet as “rudders” to aid in turning. A short leg is also useful in conserving body temperature in cold climates, although the earliest penguins probably did not need to worry about this very much given they lived during a much warmer time in Earth history.
How do these short legs effect movement on land? Some early scientists had proposed that the waddling gate of penguins, alternatively considered awkward or endearing depending on your point of view, wastes energy. As it turns out, waddling is actually an energy saver. In 2000, researchers Timothy Griffin and Rodger Kram conducted studies on shuffling penguins and found that the weird way they move makes sense metabolically. Essentially, as a penguin waddles side to side, each sway stores energy for the next step, somewhat like a pendulum. By measuring the force generated with each step using a special platform, the scientists determined that penguins conserve about 15% more energy between steps than humans. Thus it turns out that the short feet of penguins are not the most efficient set-up, but this inefficiency can be partially overcome with a novel gait.
You can really see the side to side motion of the penguin waddle in this video:
Griffin, T.M. and R. Kram. Biomechanics: Penguin waddling is not wasteful Nature 408, 929.
Last post, we discussed a new type of pigment discovered in the feathers of living penguins. With a little bit of evolutionary tree-based reasoning, it is possible to project the distribution of this color back into the fossil record as well. In his blog Illuminating Fossils, Dr. Daniel Thomas does just that. Check out the post to see how we can reconstruct the color of the fossil penguin Madrynornis. You can also learn more about Madrynornis in this past post.