Archive for March 2017
As we mentioned last post, March of the Fossil Penguins will be covering some exciting new research over the next three years. I’m very fortunate to be involved in a new project working with Dr. Tracy Heath and Dr. Rob Meredith. One of the main goals of the grant is to develop more sophisticated computer models to reconstruct evolutionary trees that include both living and fossil species. We chose penguins as one of our “test cases”, because they have a rich fossil record with lots of specimens and well-constrained geological dates.
We are excited about sharing our results with the public, and helping build computer literacy is one of our major outreach goals. As part of the project, the Bruce Museum’s amazing Paul Griswold Howes Fellow, Kate Dzikiewicz, has been hitting the road to bring an Hour of Code to hundreds of students. Computer coding is one of the most widely useful skills students can learn, as basic coding abilities can be used in careers ranging from the biological sciences to graphic design. Hour of Code is a global initiative that aims to bring an hour of computer coding lessons to as many students as possible, and we are putting our own spin on it, with a little help from a new virtual friend named Kari the Kairuku penguin.
Kate created Kari to make coding more fun. She is based on an ancient penguin who lived in New Zealand 27 million years ago, and reached a height about a foot and a half taller than an Emperor Penguin. Kids learn techniques for guiding Kari’s movements, looping actions, adding animations and more. Then, they can turn their imaginations loose and code up their own adventure for Kari.
Check out the story of Kari here: https://scratch.mit.edu/projects/130254722/
This week, a new study of the penguin evolutionary tree officially appeared in Systematic Biology (though the proof has been available online ahead of formal publication). This represents the first paper from an exciting new project aiming to develop Bayesian methods for combining data from fossils and living species. I’ll be teaming with the exceptional duo of Dr. Tracy Heath of Iowa State University and Dr. Rob Meredith of Montclair State University on this project, and penguins will be one of the “test pilot” groups to try out the new methods.
Our first foray into this realm was to re-analyses a dataset that was originally developed for a parsimony analysis of the giant fossil penguin Kairuku in 2012. This dataset includes 245 morphological characters and >6000 molecular characters. Our re-appraisal was led by PhD student Sasha Gavryushkina of Auckland University. We applied the Fossilized Birth-Death Process, a model pioneered by Dr. Heath that explicitly acknowledges that extant species and fossils are representatives of the same macroevolutionary process, in a tip-dating framework which allows fossil ages to be incorporated into the tree directly. Our analyses thus allow the ages of the fossils to directly impact the shape of the tree, and in a new wrinkle also allow for the possibility that some fossils species may be ancestors to one or more other species.
The results are shown below. One pattern that emerges immediately is that penguins are a very old group, extending back past 60 million years, but that crown penguins only started radiating between 13 and 14 million years ago. Thus, we have evidence for a recent wholesale replacement of “primitive” penguins by “modern” forms. Our work also benefits from some recent geological work, which for example has shown that Spheniscus muizoni, a fossil penguin thought to be 11-13 million years old, is actually close to 9 million years in age. In one reversal of previous findings, the fossil penguin Madrynornis mirandus is pulled outside the Eudyptes–Megadyptes clade in our study.
To me, the most intriguing message comes from the dates: modern penguins are young. Our dates are much younger that those recovered by past studies that looked only at DNA from living penguins. Adding the fossil data has a major effect, and it is very important: because about 3/4 of all known penguin species are now extinct, ignoring the fossils is like looking at just one small piece of a large puzzle. Our new dates place the origin of modern penguins at a really interesting time in Earth history: the Middle Miocene Transition. This transition marks the start of a global shift from warmer to cooler climates that ultimately leads to the glacial-interglacial cycles of our modern world. The accompanying expansion of Antarctic ice sheets may have opened up new habitats for penguins. In deed, we find that the peaking of glacial advance-retreat cycles in the Pleistocene may have been a driver of penguin evolution: 12 of the 18 living species likely arose in the last 2 million years according to our results.
Over the next three years, our team will be working on improving these methods and expanding their capacity to incorporate other types of data, such as the geographic locations of fossils and how frequently fossils occur within their overall stratigraphic ranges.
Gavryushkina, A., T.A. Heath, D.T. Ksepka, T. Stadler, D. Welch, and A.J. Drummond. 2017. Bayesian total evidence dating reveals the recent crown radiation of penguins. Systematic Biology 66 (1): 57-73.
How old are penguins? A new article reports some of the most ancient fossils yet, and discuss their implications of penguin evolution. The bones in question are elements of the hind limb: the good old tarsometatarsus (the bone that forms the main body of the foot) and several phalanges (toe bones). They were discovered in New Zealand in the Waipara Greensand. which is the rock unit that yielded Waimanu manneringi. Both fossils are about 61 million years old, making them the oldest penguins known.
Despite being the same age as Waimanu manneringi, the new fossils are more “penguiny”, at least when it comes to the foot morphology. Whereas Waimanu manneringi has a slender tarsometatarsus with a raised articulation for the second toe like many non-penguin birds, the new fossil has a much stouter tarsometatarsus that resembles penguins that are several million years younger. The heftiness suggests it might belong to a much heavier bird than Waimanu manneringi. Overall, a number of fine features suggest the new Waipara penguin occupies a branch on the evolutionary tree that is one step closer to modern penguins than any other species swimming around 61 million years ago (though to clear it was still a very distant relative of any living species).
The authors of the new paper suggest that there must have been more than just 5 million years for such a variety of penguins to evolve, pushing the origin of penguins into the Cretaceous Period. Does this mean we are going to eventually find penguins in rocks from the Cretaceous Period? Personally, I am skeptical we will find a flightless penguin that old. We have found tons of penguin fossils from the Paleogene Period, but not a single such bone from the Cretaceous Period. So, it seems likely penguin evolved into flightless wing-propelled divers after the K-Pg mass extinction, which wiped out the dinosaurs and marine reptiles like plesiosaurs and mosasaurs. It is of course possible that the flying ancestors of penguins were roaming around during the Cretaceous, though this would be harder to prove because the delicate fossil bones of flying birds have much less of a chance of being preserved than the dense bones of diving birds. That would be quite a find.
Mayr, G., De Pietri, V.L. & Paul Scofield. 2017. A new fossil from the mid-Paleocene of New Zealand reveals an unexpected diversity of world’s oldest penguins. The Science of Nature 104:9.