March of the Fossil Penguins

Fossil penguin discoveries and research

Posts Tagged ‘Fossil species roll call

Killer Bobble-Headed Penguins!

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Spheniscus penguins are your basic model.  Collectively, the four living species are sometimes known as “tuxedo penguins” for their striking color patterns, which resemble a tuxedo motif just a bit more than those of other types of penguins. These four species are among the most warm-weather adapted of modern penguins, and live in Africa, South America and the Galapagos Islands. Spheniscus penguins also have a really good fossil record, with lots of skeletons discovered in the past few years in places like Peru and Chile.  Many of these specimens are very similar to the living Humboldt Penguin (Spheniscus humboldti), which plies the coasts of South America today. However, two species stand out for their remarkable appearance.

Spheniscus urbinai and Spheniscus megaramphus were discovered in the prolific fossil deposits of the Peruvian Atacama Desert (also referred to a the Sechura Desert). These penguins appear to be standard, although slightly larger, versions of the basic Spheniscus plan from the toes up the neck.  Flippers, legs, vertebrae – all these bones are not easily distinguishable from the same elements in a Humboldt Penguin to the untrained eye.  The head, though, is a different story.  These two penguins have “bobble heads” – skulls that are proportionally too big for their body. Well, too big for a normal penguin’s body anyway – no one seems to have sent a memo to Spheniscus urbinai or Spheniscus megaramphus.  Aside from the big heads, these penguins had killer beaks.  The tips, instead of being straight like many fossil penguins or lightly down-turned like most modern species, were powerfully developed into a sharp menacing hook.  This is a style of beak often seen in aeriel predators like eagles and fish-snatching birds like frigatebirds.

Skulls of a “normal” Humboldt penguin (top) and Spheniscus megaramphus (bottom).

One of the basic facts about fossil bird beaks is that they tend to tell only half the story.  That is because the bony part of the beak is covered by a layer of keratin in life.  This sheath can greatly extend the tip of the bill in some species, and Spheniscus penguins are a perfect example.  The bony beaks of these birds have a modest sharp hook at the tip.  When the sheath is added though, the tips start looking pretty fierce. Adding the keratin layer to Spheniscus urbinai and Spheniscus megaramphus would rachet up the beak from menacing to downright scary. What were these fossil species doing with there intimidating beaks? Most likely catching tough prey.  A powerful hook  would be  well suited to ripping into fish and squid, and is more useful for holding onto a larger victim than gathering up tiny things like sardines.  Whatever their ecology, the bobble-headed Spheniscus species did not make it to the present day.  After splitting off from the main Spheniscus lineage around 6 million years ago, Spheniscus urbinai and Spheniscus megaramphus enjoined a few million years of successful hunting before vanishing.

A crude rendering of the body outline of Spheniscus urbinai with a living Spheniscus penguin for scale.

Written by Dan Ksepka

September 25, 2012 at 4:22 pm

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Introducing Kairuku!

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Today, two new fossil penguin species formally enter the scientific catalog.  These 27 million year old penguins are unique, “svelte” species with graceful proportions discovered in New Zealand.  I worked on these incredible fossils in 2009 and 2011 with Dr. Ewan Fordyce of the University of Otago and former Otago students Dr. Tatsuro Ando and Dr. Craig Jones (now at the Ashoro Museum of Paleontology and Institute of Geological and Nuclear Sciences, respectively) on a scientific article describing the new species and the new details they reveal about penguin evolution.  Our findings are now published in the latest issue of the Journal of Vertebrate Paleontology.

So, what makes Kairuku so special?  The three skeletons discovered are among the most complete ever recovered for an ancient penguin.  They reveal that Kairuku penguins cut a striking figure.  They had more slender proportions than living penguins, with an elongate trunk, narrow bill, and long, narrow wing bones.  The legs, on the other hand, were quite robust.  Overall, the skeleton conveys a very elegant bird, sleek yet powerful.  And, they were tall.  A standing Kairuku penguin would have reached about 4 feet 2 inches, more than a foot taller than an Emperor Penguin. Artist Chris Gaskin created a meticulous reconstruction of the new species that really drives these features home.  You can practically feel the wind whipping sand and ocean spray into the air as the two penguins come ashore.

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.

The name Kairuku is taken from Maori language, and loosely translates to “diver who returns with food”.  Kairuku waitaki is named for the large river that flows through modern Canterbury and Otago.  Kairuku grebneffi is named in honor of the late Andrew Grebneff, who contributed to the field collection and preparation of many of the fossil specimens of both species.

The first Kairuku specimens were discovered by the great New Zealand zoologist and paleontologist Dr. Brian J. Marples  in the 1940s, but these bones were not immediately recognized as belonging to a new species because they were not very well preserved and typically included only a few pieces of the wing skeleton.  Highly complete skeletons were later recovered by Dr. Ewan Fordyce, starting with a wonderful discovery along the banks of the Waihao River in 1977.  This skeleton, a beautiful set of orange fossil bones embedded in soft greensand matrix, would turn out to be the holotype specimen of Kairuku – the standard by which all Kairuku specimens shall henceforth be compared to.  Over the next 35 years, many more Kairuku specimens have been found.  In fact, the most recent was collected only two months ago during our field excursion in New Zealand.

Written by Dan Ksepka

February 27, 2012 at 2:01 pm

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Meet Inguza, the Smallest Penguin from Africa

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Inguza is fast becoming one of my favorite fossil penguins.  Last December, I spent several weeks in South Africa studying fossil penguin bones in museums and at field sites with my friend and colleague Daniel Thomas.  Much of our time was spent examining, measuring, and analyzing bones of a somewhat runty penguin named Inguza predemersus.  This species was on the small end of the scale, and would have stood about chin-high next to the living Blackfooted Penguin (a species that is also known as the Jackass Penguin or the African Penguin).  Bones of Inguza are very common in the Langebaanweg Quarry, a famous fossil site that has produced some of the most amazing fossils in Africa, including the remains of a miraculous short-necked giraffe and Africa’s first fossil bear (completely unexpected as no bears live on the continent today).  Daniel Thomas and I were able to learn a lot about the evolutionary history of African penguins by studying Inguza, and I’ll post more about that soon.

A skeletal reconstruction of Inguza predemersus with extant Blackfooted Penguin (Spheniscus demersus) for scale, from Ksepka and Thomas (2011). Blackfooted penguin art by Barbara Harmon, Inguza art by Kristin Lamm

Holding the bones of Inguza side by side with bones from modern Blackfooted Penguins, I often wondered whether the two had ever met.  Among the hundreds of penguin bones from the Langebaanweg quarry, there is no trace of Blackfooted Penguin remains.  The youngest Inguza fossils are about 5.1 million years old, and the oldest Blackfooted Penguin bones are between 250,000 and 400,000 years old.  There’s a pretty large gap in the African fossil record between these points though, where few marine birds of any sort are known.  It’s possible that at some time within that interval, the last Inguza individuals noticed a new neighbor in their colonies as the founding Blackfooted Penguin population arrived.  Perhaps they lived side by side, choosing different prey. Perhaps they jostled uneasily for nesting sites.  Perhaps the new arrivals even contributed to the extinction of Inguza by outcompeting that species.

Or, its possible the last Inguza died out before any Blackfooted Penguins set foot in Africa.  In the most extreme scenario, there may have been NO penguins at all in Africa at some point 1-4 million years ago.  Blackfooted Penguins could have arrived into a “penguin vacuum” and set up shop wherever they pleased.  Not knowing what happened is one of the reasons we keep going back to the field to collect more fossils.  As we fill in the blank parts of the record, we will come closer to understanding what actually happened on those beaches millions of years ago.

Reference:

Ksepka, D.T. and D.B. Thomas. In press 2011. Multiple Cenozoic invasions of Africa by penguins (Aves, Sphenisciformes). Proceedings of the Royal Society B Biological Sciences.

Written by Dan Ksepka

September 7, 2011 at 8:41 am

Korora oliveri, a tiny mystery

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Korora is the name for the living Little Blue Penguin in Maori. It is also the genus name of one of the smallest fossil penguins, chosen to indicate the animal’s small stature.

Korora oliveri is not the smallest fossil penguin ever discovered – that honor belongs to Ereticus tonnii.  In fact, Korora oliveri would probably have stood about as tall as your average aquarium Humboldt penguin, although this estimate is not very exact because this species is only known from a single bone.  Korora is remarkable because the fossil record of penguins is dominated by larger taxa. The vast majority of fossil penguins were at least as big as the King Penguin. Very few small species are known until we reach the more recent geological epochs.

Korora lived in New Zealand during the late Oligocene, about 25 million years ago. It swam alongside giants – most of the other penguins known from this area and time are huge, towering creatures including some of the largest that ever lived.   It seems like smaller penguins were very rare in the area – as more and more large penguin fossils have been harvested from the relevant rocks they overwhelmingly belong to large species.  This suggests that penguins focused on a different niche in the Oligocene. Most species probably were eating larger fish and sitting higher up the food chain, playing a role more like that of seals than modern penguins.

Korora remains a puzzle for penguin paleontologists.  With only a single specimen, it is very difficult to figure out where this species belongs in the penguin evolutionary tree.  If it turns out to be closely related to its larger contemporaries, then it would provide evidence for dwarfing in an ancient penguin lineage – perhaps downsizing from its ancestors in order to exploit smaller prey.  If, on the other hand, Korora is more closely related to living penguins than these large taxa, it may be the herald of the modern penguin radiation – smaller, avoiding direct competition with marine mammals, perhaps more specialized for catching krill than fish.  Trying to determine which of these hypotheses is correct is futile at the moment – we need more fossils to even start understanding what this penguin ate or how modern its skeleton was.  This is why paleontology is such an exciting science.  Some questions can be answered by more work, others only by new discoveries. Korora awaits the latter.

The single bone of Korora ever discovered.

Written by Dan Ksepka

August 14, 2011 at 5:51 pm

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Eretiscus tonnii – The smallest fossil penguin

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Many of the most heralded discoveries of fossil penguins are from giant species.  Not all extinct penguins were large, however, and a few were quite tiny.  The smallest fossil species yet discovered belongs to a diminutive penguin from the Miocene (about 22 million years ago) of Argentina.  George Simpson described this fossil in one of his last scientific publications on fossil penguins in 1981.  The first specimen was a tarsometatarsus (that foot bone that keeps popping up in penguin paleontology) and some wing bones have subsequently come to light.

The fossil in question was originally given the genus name Microdytes, meaning “tiny diver”. However, this name is now obsolete because an even tinier diver – a beetle – already had claim on the name “Microdytes“.  Beetles have a pesky habit of preoccupying names applied to vertebrates.  To be more accurate, vertebrate paleontologists don’t always thoroughly check all taxonomic records before naming new fossils. The most famous example is the case of the theropod dinosaur Syntarsus.  This genus name was already occupied by a Malagasy beetle, and so some entomologists took it upon themselves to create a new name for the dinosaur: Megapnosaurus.  This translates to “big dead lizard”, a probable sling at the overly generous share of public interest dinosaurs receive compared to beetles. In a zoological wild west, a penguin might be able to bully a beetle out of a prime name.  However, that’s not the way things work in the real world.  The rule of priority means that the first species to be given a name in a formal scientific publication keeps it.  So Microdytes stays with the beetle.  The penguin was thus re-christened Eretiscus by Storrs Olson, who first noticed the conflict. The new name means “tiny rower” in reference to the penguins flipper-based locomotion.

Eretiscus was very small.  The Little Blue Penguin is the smallest living penguin, reaching only about 1kg in weight – a virtual rubber duck in size (and squeak).  At only about 1.5 feet tall, these little guys are less than knee high on most humans. Originally, Eretiscus tonnii was reported as being even smaller.  However, only one skeleton of the modern Little Blue was available for comparison when Simpson described the fossil find.  The tarsometatarsus of Eretiscus was a millimeter and a half smaller than the tarsometatarsus of that Little Blue skeleton, but other smaller skeletons exist in collections of museums.  So the fossil was not the smallest individual penguin ever, but the species may well have been the smallest (we don’t have enough samples to figure out the average).  Quibbling over records aside, we can say that small penguins have been around for a long time. They don’t seem to have been very common though. Only a few fossil bones of penguins in the Little Blue size range have been discovered worldwide versus thousands of bones of average size to giant penguins.

A humerus (wing bone) from Eretiscus tonnii

References:

Simpson, G.G. 1981. Notes on some fossil penguins, including a new genus from Patagonia. Ameghiniana 18: 266–272.

Olson, S. L. 1986. A Replacement Name for the Fossil Penguin Microdytes Simpson (Aves, Spheniscidae). Journal of Paleontology, 60(3): 785.

Written by Dan Ksepka

August 30, 2010 at 11:24 pm

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Megadyptes waitaha – The last penguin to go extinct

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Island birds have undergone some of the most fascinating radiations in evolutionary history, producing such wonders as the “toothed” Moa-Nalo ducks (Chelychelynechen, Thambetochen and Ptaiochen) of Hawaii and the enormous nine foot tall Elephant Birds (Aepyornis) of Madagascar. Island birds have also been devastated by human exploitation. The Dodo (Raphus), once an inhabitant of Mauritius, is an icon of extinction. Sadly, the Dodo is only the most well-known member of this club. Giant moa were hunted to extinction in New Zealand. Dozens of unique birds including Moa-Nalos, flightless ibises and nectar-feeding songbirds were wiped off the Hawaiian Islands following the arrival of humans. Today, many of the native bird species of Guam are severely endangered by predation by invasive snakes, introduced by humans.

Penguins were long thought to have been exempt from this fate. Because they can retreat to the sea where they are difficult to capture, penguins are somewhat less vulnerable to hunting than many other types of birds, particularly other flightless ones. Although historically harassed by humans in many ways, no penguin species was thought to have been wiped out until a very recent discovery. A team of researchers in New Zealand and Australia rounded up subfossil bones from archeological sites from the South Island of New Zealand ranging from 200 to 1500 years in age. They extracted ancient DNA from the bones and compared the sequences to other collected from live Yellow-Eyed Penguins (and museum specimens of the same species). The findings were startling – a wide genetic distance was uncovered separating the pre-1500s mainland penguin bones from post-1500s bones. The younger bones belong to the modern Yellow-Eyed Penguin (Megadyptes antipodes), and their DNA sequences cluster with samples from living individuals and subfossil bones of the species from outside the mainland. However, DNA from the pre-1500s subfossil bones from the mainland don’t cluster with the Yellow-eyed Penguin samples. DNA evidence suggests a distinct species of penguin was living on the South Island of New Zealand. This conclusion is backed up by careful comparisons of the bones, which demonstrates size and shape differences outside the range of normal variation seen in living Yellow-Eyed Penguins. The newly recognized, recently extinct species was named Megadyptes waitaha by the team.

Bones of the living Yellow-Eyed Penguin Megadyptes antipodes (left side of each pair) and the recently extinct Megadyptes waitaha (right side of each pair).

Dating of the fossil deposits suggests that Megadyptes waitaha survived all the way up to the time of colonization, overlapping with the fist human settlers to arrive from Polynesia. Direct evidence from associated artifacts shows that humans actively hunted these penguins, and the circumstantial evidence from timing strongly points to overexploitation as the proximal cause of their extinction. A second interesting finding of this study is that the modern Yellow-eyed Penguin seems to have benefited from the extinction of Megadyptes waitaha. Comparisons of the morphology of subfossil penguin bones, along with DNA extraction, reveals that in the 1500s the Yellow-eyed Penguin was restricted to sub-Antarctic islands such as the Auklands. During this same time period, Megadyptes waitaha inhabited a wide swath of the east coast of the South Island. Flash forward to 1800, and Megadyptes waitaha is nowhere to be found anywhere. Yellow-eyed Penguins crop up nearly everywhere that Megadyptes waitaha used to be. The timing suggests that as hunting patterns shifted, prime penguin real estate vacated by Megadyptes waitaha was reclaimed by Megadyptes antipodes.

So, Megadyptes waitaha is now a ghost on our collective consciences. These bones are something to think of when penguin populations suffer from oil spills, rampaging stray dogs, or overdeveloped beaches. There were at least 20 species of penguins when humans first appeared, and now we have 19 species left to enjoy and protect.

References:

Boessenkool, S.; Austin, J.J.; Worthy, T.H.W.; Scofield R.P.; Cooper, A.; Seddon, P.J.; Waters, J.M. 2009. Relict or colonizer? Extinction and range expansion of Penguins in southern New Zealand. Proceedings of the Royal Society of London B 276:815-821.

James, H.F. and Olson, S.L. 1991. Descriptions of thirty-two new species of birds from the Hawaiian Islands: Part 2. Passeriformes. Ornithological Monographs, 46: 1-88.

Olson, S.L. and James, H.F. 1991. Descriptions of thirty-two new species of birds from the Hawaiian Islands: Part 1. Non-Passeriformes. Ornithological Monographs, 45: 1-88.

Written by Dan Ksepka

August 15, 2010 at 4:01 pm

South Africa’s Nuclear Penguin

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South Africa, host of the next World Cup, is one of the best places on Earth to see penguins in the wild.  Only one species of penguin lives there today (the Jackass Penguin Spheniscus demersus), but it is possible to visit quite up close with these charming birds. The Jackass Penguin earns its name for its abrasive braying call rather than any foolhardy behavior.  Historically, this species has place of pride as the first penguin to be encountered by European explorers.  This momentous occasion occurred as Vasco da Gama’s voyage around the Cape of Good Hope landed for supplies near present day Mossel Bay in 1497 (of course, native peoples in South America, Africa, New Zealand and Australia were certainly well aware of penguins for hundreds if not thousands of years prior to this encounter).  It is not recorded how the penguins greeted their strange visitors, but the humans behaved as customary when encountering wondrous new life forms by plundering a good number of them to eat.  Relations have since improved between our species and theirs, and Jackass Penguins are a fixture at many aquariums and zoos worldwide.

While Spheniscus demersus is the only species surviving on the coast of Africa today, several fossil species have been described.  Interestingly enough, all South African penguins are from the Miocene-Pleistocene Epochs – substantially younger than the oldest fossils from other continents.  Whether penguins arrived to Africa late, or we simply have not searched diligently enough for them in older rocks, remains to be seen. One interesting and fortuitous fossil discovery from South Africa was the unearthing of Nucleornis insolitus during excavations for the Koeberg nuclear power station.  Geroge Gaylord Simpson, featured in the last post, named the species in 1979. The etymology of the genus name should be obvious.  Unfortunately only two foot bones – tarsometatarsi in avian anatomical lingo – were found.  Because the purpose of the excavation was to sink a foundation for the power plant, not search for penguin fossils, little effort was devoted to deciphering the age of the rocks in which the penguin bones were found.  They are thought to be Miocene in age – roughly between 5 and 23 million years old, and probably closer to the lower end of that range. Very little is known about Nucleornis insolitus because we have so little of the skeleton.  Based on the foot bones, the species was comparable to the living Jackass Penguin in size.  In all of the preserved morphological details, the tarsometatarsus resembles that of living penguins.  While it is not possible to definitively say whether Nucleornis shared the most recent common ancestor as the living penguin species, it was at least very closely related.  These scraps of fossil represent one piece of the puzzle of how penguins arrived and radiated in Africa, but much more work remains to be done before we will understand the whole story.


References:

Simpson, G.G. 1979. A new genus of Late Tertiary penguin from Langebaanweg, South Africa. Annals of the South African Museum 78: 1–9.

Written by Dan Ksepka

May 29, 2010 at 11:36 pm

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Paraptenodytes – Simpson’s Great Discovery

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In 1933 the famous paleontologist George Gaylord Simpson led an expedition to collect fossils around the town of Trelew in Patagonia. At this time, Simpson was still a young man. Later he would become one of the “four horseman” of the New Synthesis of evolutionary theory, bringing the deep time perspective of paleontology into a new perspective on evolution unifying natural selection and genetics.  In 1933, though, he was focused just on the excitement of collecting fossils.  Near Trelew, the Chubut River meets the Atlantic today.  It seems that this area also comprised a rich estuarine ecosystem in the past and both terrestrial and aquatic animals gathered, lived, and died here, quite often making it into the fossil record. During the trip, the team collected many mammal fossils but also repeatedly came upon penguin bones.  These were not the focus of the trip, but no good paleontologist would leave well-preserved fossils in the field regardless of what type of animal they belong too.  More than a hundred scattered bones of average sized penguins were gathered up, but one find in particular changed the face of penguin paleontology.  This specimen was a roughly 20-25 million year old, nearly complete skeleton of a single bird – a rather large one by modern standards, approaching King Penguin size.  Most of the leg, part of the flipper, many vertebrae were intact. Most importantly, the skull was there too – the first time a skull had ever been found for a fossil penguin.

At the conclusion of the successful field season, the team returned to the US with a bounty of fossils to prepare and study.  Simpson was, as mentioned, a mammal paleontologist, more interested in marsupials and such than in birds.  Thus, he attempted to pass the fossil penguin skeleton to one of the American Museum of Natural History’s many ornithologists.  None, however, took him up on the offer.  At the time, ornithologist’s were absorbed in details of the feathers and beaks of birds and had little interest in the bones of a penguin. Collections of stuffed skins were emphasized over osteological collections at the time (and still are in many museums) and so most ornithologists probably had scant appreciation for skeletal remains of any kind of bird.

Around this time, World War II interrupted George Simpson’s pleasant work on fossils and he served several years in the Army as a staff officer to Patton.  By his own account, this was a low in his career and he longed to get back to scientific pursuits. With the conclusion of the war, he happily returned to the American Museum of Natural History.  Simpson found the penguin still unstudied, and tired of the poor bird languishing set about studying it himself.  This resulted in a monumental 1946 paper titled simply “Fossil Penguins”.  The skeleton was identified as belonging to the species Paraptenodytes antarcticus, previously known only from a few bones.  Besides describing the skeleton, Simpson’s monograph revised the dozens of fossil species that had been named by this time (discarding many ill-founded ones) and definitively traced the ancestry of penguins to a flighted bird, laying to rest some bizarre theories about flightless terrestrial birds or even reptiles as penguin ancestors.

George Gaylord Simpson's specimen of Paraptenodytes antarcticus, with reconstructed body outline. Some bones have been omitted for logistical reasons.

Simpson’s Paraptenodytes specimen was the key that opened the door to the modern study of penguin evolution.  Up to this time, almost all the penguin fossils that had been found were isolated bones.  This made it difficult to reconstruct what these extinct species might have looked like and how similar or different their lifestyles were from living penguins.  Paraptenodytes antarcticus gave us the first good look at an extinct penguin species.  The species certainly had a strong bite compared to living penguins, based on the insertions areas on the skull for the muscles that work the jaw.  The flipper is rather slender and intermediate between Eocene penguins and modern species in most aspects of the underwater flight muscle placements.  The leg is pretty standard, with the typical short stubby feet of today’s penguins.   Overall, compared to the older species known from Antarctica and New Zealand, Paraptenodytes was closer to having a modern skeletal plan. Morphologies of the skull were interpreted by Simpson as evidence of a close relationship between the Sphenisciformes (the penguin clade) and  the Procellariiformes (albatrosses and allies), a hypothesis that is well-supported by DNA evidence today.

This work was not to be Simpson’s only venture in to the world of fossils penguins.  Penguin are addicting, you see, and Simpson subsequently wrote around 20 additional scientific papers on penguins, named a dozen new species and visited every one of the living penguin species in the wild.  So by chance discovery (and the recalcitrance of the ornithologist’s at the museum), one of paleontology’s greatest minds was brought to bear on the evolution of this wonderful group.

Written by Dan Ksepka

May 19, 2010 at 11:08 am

The Puerto Madryn Penguin

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Madrynornis mirandus is one of the better known fossil penguins, represented by almost the entire skeleton (although only one individual has been found so far).  This species lived about 10 million years ago in Argentina.  It was actually found almost 100km away from the city of Puerto Madryn along Golfo San José, but is named for the Puerto Madryn Formation. Madrynornis mirandus was about the same size as a modern Adélie penguin, which should be familiar to many as it is a popular zoo animal.  The species appears to have been a dietary generalist. From its based on bill shape, it probably ate fish and crustaceans.  In fact, there seems to be a fish – and a large one at that – preserved right next to the Madrynornis holotype specimen.  The disk-like bones near the feet of the penguin specimen are clearly not avian but instead belong to bony fish.  They are still lined up in a row, but there does not seem to be any other parts of the fish preserved, at least in the picture.  This particular specimen was of course much too big for Madrynornis to have tackled.

Skeleton of Madrynornis, modified from Accosta Hospitaleche et al (2007).

Madrynornis mirandus is important because it is a crown clade penguin.  This means the species shares the most recent common ancestor of all living penguins.  Penguins that branched off the evolutionary tree before this common ancestor evolved are called stem penguins. One can imagine these archaic penguins occupying the lower, “stem” part of a branching plant and the crown penguins occupying the tree top, or crown.  All stem penguins are by definition extinct, while crown penguins may be either living or extinct – a mix of green and brown leaves in the canopy.

Phylogenetic studies show Madrynornis mirandus is closely related to the living Yellow-eyed Penguin (Megadyptes antipodes) and the crested penguins of the genus Eudyptes.  As the name suggests, the Yellow-eyed Penguin has a bright yellow eye with a stripe of yellow feathers across it. Eudyptes penguins are characterized by a crest of yellow head feathers that gives them a somewhat fancy visage.  One of the best known Eudyptes penguins, the Macaroni Penguin (Eudyptes chrysolophus) is actually named after a style of feathered hat fashionable the 1800s, not the noodle.

Examples of the head feathering of Megadyptes (left) and Eudyptes (right).

Knowing that Madrynornis mirandus is related to these living penguins enhances our inferences about the species.  Because the fossil occupies a branch on the tree in between the Megadyptes and Eudyptes branches, we can say that it is bracketed by those two living species.   This extant phylogenetic bracket concept was formalized by Dr. Larry Witmer and has been applied to many paleontological questions.  Many soft parts of an animal, like skin and feathers, don’t typically fossilize.  However, if we understand the evolutionary tree for a group and study the closest living relatives of the extinct species, we can make some extrapolations about these soft tissue features.  The strongest basis for inferring the morphology of a non-fossilized feature is when both living taxa that bracket the extinct species possess a feature – then we can safely assume the feature was probably present in the fossil too.  In the case of Madrynornis mirandus, we can be fairly confident the extinct species also had decorative yellow head feathers.  The evolutionary tree helps us “flesh out” the appearance of this long extinct penguin without having to just guess.

Another important aspect of crown fossils is that they can help us reconstruct the timing of evolutionary events.  Because Madrynornis mirandus occupies a branch in between the Eudyptes penguins and the Megadyptes penguins, we know these two groups must have separated off onto their own evolutionary pathways by at least 10 million years ago.  This is an important piece of data that can unlock a lot of information about the pattern and timing of penguin evolution.  We’ll cover how in a future post.

References:

Acosta Hospitaleche, C., C. Tambussi, M. Donato, and M. Cozzuol. 2007. A new Miocene penguin from Patagonia and its phylogenetic relationships. Acta Palaeontologica Polonica 52: 299-314.

Witmer, L. M. 1995. The extant phylogenetic bracket and the importance of reconstructing soft tissues in fossils. In Functional morphology in vertebrate paleontology (ed. J. J. Thomason), pp. 19–33. Cambridge University Press

Written by Dan Ksepka

April 11, 2010 at 10:36 pm

The Largest Penguin Ever?

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What was the biggest penguin ever?  It’s a popular question.  Today, as every schoolchild knows, the largest penguin is the Emperor Penguin.  That species measures about 3 feet tall, when standing with its feet flat and it head at resting posture. We already know that some extinct penguins got much bigger.  But, paleontologists are not certain which was the largest ever. Two contenders are Anthropornis nordenskjoeldi and Pachydyptes ponderosus.  The scientific names of these penguins reference their mighty stature.  Anthropornis translates to “man bird” and Pachydyptes to “stout diver”.   Sadly, only isolated bones have been found from the two species.  Yet there is no denying they were tremendous birds – compare the major wing bone of Pachydyptes to a typical penguin below.

Humerus (wing bone) of the giant penguin Pachydyptes ponderosus compared to the humerus of a typical living penguin.

Extrapolating the total size of an extinct animal from a few bones is a  real challenge. Despite the impressive size of the bones we have found so far, it is not even clear whether either of them was the biggest penguin of all time.  Part of this issue depends on what we mean by “biggest”.   The tallest and heaviest species within any given clade of animals is not necessarily the same – just think of the tallest and heaviest land mammals alive today – the giraffe and an elephant.  If we go by the length of the humerus (the major bone of the flipper), there are actually penguins out there that would come out a few millimeters ahead of Pachydyptes.  But if we go by the length of the coracoid (a bone of the shoulder girdle), Pachydyptes wins hands down against all other penguins.

The proportional differences between a fossil penguin and the average living species are not as extreme as those between an elephant and a giraffe, but there is a lot of uncertainty. For example, if we compare the wing bones of Pachydyptes to an Emperor penguin, they are about 35% longer but almost twice as thick.  It gets even more complicated when we see that the shoulder girdle bones are only slightly longer but also a different shape.  So we can’t just scale directly – we need to find a complete skeleton to truly understand what is going on. Even amongst living penguin species the relative proportions of the beak, legs, flippers and trunk vary fairly widely and fossil penguins do not always fall even within that range.  Was Anthropornis taller because it was perched on long, slender limbs?  Was Pachydyptes ridiculously short-necked with thick, short legs?  Dimensions from the bones we have give us some clues as to standing height of the largest penguins, but without the hindlimb, pelvis and vertebral column there is always going to be a wide range of error.

Still, we can get to a ballpark total. George Simpson did some back-of-the-envelope equations back in 1946 and put the tallest penguins at around 5 feet tall.

Simpson's (1946) line-up of penguins showing the rough size of the largest fossil species (B), some more modest fossil species (C,E) and the living Emperor Penguin (D) and Galapagos Penguin (F). As noted by Simpson (1946), these are not meant to be exact reconstructions of particular fossil species, but rather to give an idea of scale.

Weight is a separate issue from height.  Personally, I have little doubt that Pachydyptes was the heaviest fossil penguin (at least the heaviest discovered so far).  The wing bones are just so wide compared to other similarly sized species that the animal, from little we know of it, appears to have been extremely stocky.  Imagine the Chicago Bears defensive lineman William “The Refridgerator” Perry with flippers.  Piotr Jadwiszczak used regression equations relating the limb bone proportions of living penguins to mass, and estimated the largest species would tip the scales at over 170 pounds.  Another rough estimate for the present, but nonetheless evocative. Pack this mass into a 5 foot frame and you have penguin that could bowl over pretty much anything in its way.

So the answer to the opening question is – we don’t know what the biggest penguin species is, or exactly how big it got.  This is no reason to become frustrated.  It’s one more question about extinct birds we can seek an answer to by continuing to search for new fossils and better methods of reconstructing total mass from the dimensions of individual bones.

Written by Dan Ksepka

February 22, 2010 at 11:38 pm

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