March of the Fossil Penguins

Fossil penguin discoveries and research

A New Look at the Penguin Evolutionary Tree

leave a comment »

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 EudyptesMegadyptes clade in our study.

penguins.jpg

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.

 

Reference:

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.

Written by Dan Ksepka

March 13, 2017 at 11:23 am

Posted in Uncategorized

A Surprising Advanced Paleocene Penguin

with 2 comments

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 manneringiBoth 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).

penguin-press-1

Foot bones of a new fossil penguin from the Waipara Greensand (left) compared to the same bones from an Emperor Penguin (right). Photo courtesy Dr. Gerald Mayr.

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.

 

Reference:

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.

Written by Dan Ksepka

March 3, 2017 at 10:25 am

Posted in Uncategorized

Taking another look at the Glen Murray Penguin

leave a comment »

Today is Penguin Awareness Day! What better day to get back to blogging about fossil penguins. In this morning’s post, I’d like to summarize a recent project on New Zealand’s fossil penguins.

A short while back, Dr. Daniel Thomas and I had the chance to team up for our fourth penguin paper together. We re-examined the fossil known as the “Glen Murray Penguin”, a set of leg bones collected from rocks that are roughly 30-35 million years in age. This fossil is important because it is one of the few records of fossil penguins from the North Island of New Zealand (specimens from the South Island are plentiful).

cfy5o0jwmaacaig

Daniel Thomas (right) and I peruse the Bruce Museum’s duck and goose taxidermy collection.

The fossil bones were first reported over 30 years ago, by Jack Grant-Mackie and George Gaylord Simpson (subject of our previous post). At the time, the taxonomy of fossil penguins from the region was still rather poorly known. Few reasonably complete skeletons had been collected, so it was rather difficult to tell which species that new isolated discoveries belonged to.  Thus, the significance of the Glen Murray specimen for penguin diversity remained largely unresolved since initial description. One thing is certain though – it was a huge penguin! The bones make those of your average zoo penguin look like miniature carvings.

img_1591

3D printed leg bones of the Glen Murray Penguin, with the same bones from a Chinstrap Penguin for scale.

Dr. Thomas invited me to work on the specimen with him, and provided a wonderfully modern aid to collaboration. Although I had seen the Glen Murray Penguin in person in 2012, it was hard to make comparisons from just my photos. So, Dr. Thomas sent scanned the fossil with a laser scanner, printed out a 3D copy, and sent it right over. It was spectacular to be able to hold a precise replica of a fossil while the real thing was sitting on the other side of the world, and of course this helped facilitate our discussions.

After some anatomical work, we determined that the Glen Murray penguin shares two key  traits that are only seen in the extinct genus Kairuku: the femur is very stout and the end of the tibiotarsus has a distinctly convex inner face. This led us to conclude that the Glen Murray penguin is most likely a new species of Kairuku which is distinct from its southern brethren, though we decided to wait until more of the skeleton is found to test this hypothesis before we go about applying names. Hopefully we will learn more about this penguin as more fossils are collected on the North Island – something I am sure Dr. Thomas has big plans to make happen!

Kairuku penguin & stranded Waipatia

Two Kairuku penguins come ashore, passing a stranded Waipatia dolphin. Artwork by Chris Gaskin, owner and copyright owner: Geology Museum, University of Otago. Used with permission.

References:

Grant-Mackie M.J.A., and G.G. Simpson. 1973. Tertiary penguins from the North Island of New Zealand. J Roy Soc New Zeal. 3:441–451.

Thomas, D. B., and D. T. Ksepka. 2016.  The Glen Murray fossil penguin from the North Island of New Zealand extends the geographic range of Kairuku. Journal of the Royal Society of New Zealand:doi/abs/10.1080/03036758.2016.1211541.

Written by Dan Ksepka

January 20, 2017 at 11:23 am

Posted in Uncategorized

Happy Birthday to George Gaylord Simpson

leave a comment »

Today would have been the 114th birthday of George Gaylord Simpson had he lived to that implausible age. Simpson is well known for his paleontological research and his role in formulating the “new synthesis” of evolution. Although much of his work focused on fossil mammals, Simpson also collected and studied fossil penguins. His initial foray into the world penguins was by his own account accidental. Simpson traveled to Argentina several times in the 1930s to collect fossils and brought back a large number of penguin specimens. No bird experts at the American Museum of Natural History wanted to undertake a study of the material, so Simpson himself took up the reigns and wrote a monograph succinctly titled “Fossil Penguins” in 1946. This sparked a long term interest in fossil penguins that brought him to investigate collections throughout the Southern Hemisphere, identifying many new species and revising the taxonomic arrangement of the group. My own work on fossil penguins was kindled by Simpson’s legacy. As a graduate student at the American Museum of Natural History, I had the chance to examine the specimens he collected in Argentina, prodding the ancient bones with new methods that had existed in the mid-century such as CT-scanning and advanced microscopy. One of the amazing experiences about working in museums is you quite literally get to walk in the footsteps of legends, reading hand-written field notes (which in the case of Simpson often mix meticulous outcrop maps with witty remarks).

george-gaylord-simpson-4

Aside from his many scholarly publications, Simpson wrote the popular book “Penguins: Past and Present, Here and There” in which he chronicled discoveries of living penguins and fossil penguins, including both historical events and penguin encounters from his own adventures. There is a quote near the end of the book that is simply delightful:

“What good are penguins?” It may be crass to ask what good a wild animal is, but I do think the question may be legitimate. That depends on what you mean by good.  If you mean “good to eat,” you are perhaps being stupid.  If you mean “good to hunt,” you are surely being vicious.  If  you mean “good as it is good in itself to be a living creature enjoying life,”  you are not being  crass, stupid, or vicious.  I agree with you and I am your brother as  well as the penguin’s.”  

 

Written by Dan Ksepka

June 16, 2016 at 4:57 pm

Posted in Uncategorized

Penguins are not fans of opera?

leave a comment »

Written by Dan Ksepka

May 15, 2016 at 7:23 pm

Posted in Uncategorized

Reading the Mind of the Oldest Penguin

with 2 comments

brain

The fossil skull (left) and a virtual endocast (right). Figure from Proffitt et al. (2016).

Today is World Penguin Day, which makes a good excuse to catch up on fossil penguin blogging. Recently, James Proffitt and colleagues published a study on fossil penguin neuroanatomy. As we’ve discussed previously, the brain morphology of extinct animals can be reconstructed by computed tomography (CT) scanning, which allows researchers to map out the volume and shape of the brain based on the cavity it once occupied in the skull. This paper provides the first look at the neuroanatomy of the early penguin Waimanu.
Waimanu is the oldest reported penguin taxon. It is known from Paleocene rocks in New Zealand, where two species have been discovered (Waimanu manneringi and Waimanu tuatahi). The skull that was scanned for this study belongs to the genus Waimanu, but whether it represents one of the two known species or a third new species has not yet been untangled.  Even though Waimanu is a very early penguin, probably representing a point in the evolutionary history of penguins just a few million years after the loss of aerial flight, it already shows many of the features that are typical for penguin brains. These include the widening of the cerebellum, and the lack of any impressions of cerebellar folds on the endocast (interestingly, modern penguin brains do have cerebellar folds like other bird brains, and it has been suggested that the lack of folds on the endocast is due to the “cushioning” of the brain by meningeal tissue).  On the other hand, Waimanu is primitive in showing weak development of the “Wulst”, a structure associated with complex visual processing and other functions. The Wulst becomes expanded later in penguin evolution, as seen in some of the endocasts I have studied from Eocene and Miocene penguins.
pengo

An evolutionary tree mapping endocast shape in aquatic birds.  Figure from Proffitt et al. (2016)

These new data let us push deeper into the history of penguin brain evolution. As we get closer and closer to the loss of aerial flight by probing deeper down the trunk of the tree, it will be interesting to see when some of the “penguiny” brain features that are already present in Waimanu first arose.  As a whole, endocast studies of penguins are a great example of how new research becomes possible with new technology. Five years ago, there were no fossil penguin endocasts at all, and today we have five and there are plenty of additional fossils that have already been scanned or are waiting patiently for their turn in the CT lab. Perhaps by the next World Penguin Day we will have ten endocasts?
Reference:
Proffitt, J. V., J. A. Clarke, and R. P. Scofield. “Novel insights into early neuroanatomical evolution in penguins from the oldest described penguin brain endocast.” Journal of Anatomy (2016).

Written by Dan Ksepka

April 25, 2016 at 10:12 am

Posted in Uncategorized

(Sub)fossils in Guano

with one comment

Beneski_Amherst 010.jpg

This week, I visited the Beneski Museum of Natural History at Amherst College. The museum is home to one of the most famous fossils in the world, a slab bearing the first fossil dinosaur footprints ever discovered. Remarkably, the slab was used for years as a doorstop before its importance was recognized.

While the museum’s remarkable assemblage of fossil trackways is the most unique aspect of the collections, a different type of fossil caught my eye. Within a nifty display illustrating different pathways to fossilization, a somewhat unfortunate-looking bird sits in a pull-out drawer. The specimen was collected from Guanape Island, off the coast of mainland Peru. Although it looks almost like a mangled rubber chicken, the specimen is actually hardened and pretty much reduced to the bones. The bird is encased in a thin layer of guano: that is, it is literally preserved in poop. Guano is the term scientists use for the bird and bat droppings. Guano is rich in phosphate, which under the right conditions can enhance preservation of shell and bone. In places where animals congregate in large numbers, guano may form layers than are meters and meters deep.

Guano Penguin.jpg

A closer look reveals the specimen here is a penguin: the dead giveaway is the very short wing.  This penguin is most likely a Humboldt Penguin, a species which inhabits the coasts of Peru today and happens to feel quite comfortable digging into guano layers to create burrows for nesting. Guano nesting can be hazardous, however. Humans have recognized that guano makes an excellent fertilizer for centuries, and have often excavated guano deposits with little regard for the birds using the deposits as breeding colonies, stripping them bare with rapacious greed. This approach is short-sighted, as the deposits are replenished by the birds themselves – more responsible harvesting schedules can turn guano into a renewable resource and have been adapted in recent times and many sights.

Written by Dan Ksepka

March 8, 2016 at 11:58 am

Posted in Uncategorized