06 November 2015

Fossil Vertebrate(s) of the Month: Pelycosaur Extravaganza!

Pelycosaurs (Edaphosaurus, Dimetrodon, Sphenacodon, & Ophiacodon)
From The Age of Reptiles by Rudolph Zallinger
I've been negligent about posting fossil vertebrates of the month since the beginning of the school year, so I've made November's installment an especially hearty three-course Thanksgiving feast of paleontological delicacies on which to gorge yourself.  Bon appetit!

Soup & Salad: Rudolph Zallinger & The Age of Reptiles
As long as paleontologists have been finding and describing fossils, they have relied on paleoartists to bring these organisms to life.  There have been several such artists through time, but none have had more of an impact than Rudolph Zallinger.  Born in Russia, raised in Seattle (where you can still see some of his work), and educated at Yale, Zallinger led a fascinating life.  He created several works of scientific illustration and paleoart, but two have played an especially important role in public understanding of science.  His 1965 depiction of human evolution, widely known as the March of Progress, became one of the greatest (and most endlessly parodied) icons of evolutionary biology, despite the fact that it does not do justice to the true branching complexity of human evolution (as Zallinger himself well knew).  Before this, though, Zallinger had painted the most impressive single work of paleoart ever created.  In 1941, the director of the Peabody Museum decided to liven up the museum's Great Hall (home to, among other things, the original specimen of the recently resurrected genus Brontosaurus) and selected Zallinger, still a student at the time, to carry out his vision.  The result, completed in 1947, was the 1,760 square-foot mural The Age of Reptiles (later to be joined by the smaller Age of Mammals).  As a fresco, the animals, plants, and scenery depicted in the painting remain as stunning today as they were in the '40s.  So impressive is the mural that, until the release of Jurassic Park, it probably had more impact on the public image of prehistoric life than any other work (it is, for example, widely believed that Zallinger's lumbering Tyrannosaurus had a direct influence on the design of Godzilla).  While much of what has been written about the mural has focused on dinosaurs (the subjects of the mural, incidentally, that are now the most outdated), Zallinger gets high paleoecological marks for including a wide range of organisms (especially plants) in his work and for placing them in a landscape that reflected the conditions that were thought to have existed on Earth during a given period.  For the Permian section of the mural, shown in the picture above, filling in the foreground in front of a series of soaring red cliffs (seriously, check out an uncropped image of the mural: no reconstructions of extinct organisms ever got a more dramatic backdrop), Zallinger chose for his main subjects reptiles that had been emerging from the Red Beds of Texas since the 1870s.  They are, from left to right, Edaphosaurus, Dimetrodon, Sphenacodon, and Ophiacodon.  As an artist, Zallinger no doubt chose to depict them because they were visually striking.  One of his strengths as a paleoartist, though, was his understanding of the organisms he was painting, so he was no doubt aware that these animals have an evolutionary history every bit as impressive as their appearance.

Main Course: Pelycosaurs
The four large animals depicted in the Permian section of The Age of Reptiles are known collectively as pelycosaurs, often misunderstood as a lineage of dinosaurs.  In fact, pelycosaurs are neither a lineage (the group is paraphyletic) nor are they dinosaurs (the nearest - though still quite distant - relative of dinosaurs in this picture is the small Araeoscelis scuttling along the rocks below the feet of Dimetrodon) .  Look at the skull of any of the pelycosaurs depicted in the mural and you'd see a single opening behind the eye.  This is known as the synapsid opening and it has lent its name to the large group of whose evolutionary tree pelycosaurs form the base: the Synapsida, the taxon that includes all mammals and our extinct relatives (as I frequently point out to students, this means that pelycosaurs are more closely related to us than to dinosaurs).  While often misidentified, two of the animals depicted by Zallinger, Edaphosaurus and Dimetrodon, are among the most widely recognized organisms in paleontology due to the characteristic sails on their backs.  Despite their superficial similarity, the two genera are actually not particularly close relatives.  Edaphosaurus was an edaphosaurid, a family remarkable for its stubby teeth indicating one of the earliest occurrences of herbivory among land-living vertebrates.  Teeth are also one of the remarkable features of the larger Dimetrodon, which belonged to the family Spenacodontidae (named after Spenacodon, the third of the four large pelycosaurs in Zallinger's mural).  Unlike Edaphosaurus, the teeth of Dimetrodon were serrated and clearly adapted for a carnivorous diet.  The name Dimetrodon ('two sizes of teeth') reflects the most important aspect of sphenacodontid dentition: teeth vary in size and shape along the jaw, with large teeth at the front and smaller teeth towards the rear.  While this may seem a minor point, differentiated and specialized teeth are one of the defining characteristics of mammalian evolution, and as our distant relatives, sphenacodontids represent the earliest expression of this hugely important trait.  Edaphosaurus and Dimetrodon, then, represent significant innovations in synapsid evolution - herbivory and heterodont dentition, respectively - but it should come as little surprise that much of the attention that has been lavished on them by paleontologists and the general public has focused on the elongated vertebrae and the sails they supported, which may (or may not) have implications for another defining characteristic of mammals.

Dessert: Warm-Bloodedness
It's easy to take warm-bloodedness (both endothermy - the ability internally regulate our own body temperature - and homeothermy - the ability to maintain a constant internal temperature) for granted, as it's the basis of our metabolism, as it is for other mammals and for birds.  However, warm-bloodedness is only really widespread in those two groups and, just as much recent work has focused on the evolution of endothermy in the dinosaurian ancestors of birds, there has long been in interest in identifying its origins in our own lineage as well.  Such research has often centered on the sails of edaphosaurids and sphenacodontids, as one of the leading hypotheses for their function is that they acted as a means of absorbing solar heat to power metabolism (the main alternative hypothesis is that the sails were used as display structures of some sort).  If this were the case, it would imply that, while not fully capable of endothermy, being able to maintain an active lifestyle would have been advantageous to pelycosaurs.  Thus, just as the teeth of Edaphosaurus and Dimetrodon are harbingers of the later diversity of mammalian diets, perhaps their sails were likewise precursors to the warm-bloodedness of modern mammals.  Early tests of this hypothesis focused primarily on the ability of the sails to absorb solar heat or, in the case of the unusual knobs on the spines of Edaphosaurus, to create a turbulent airflow around the sail that would allow a more efficient uptake of energy.  More recently, several analyses of bone structure have shed new light on the question.  One working group in particular (that includes former UW paleontologist Adam Huttenlocker) has looked into the histology of Sphenacodon, Edaphosaurus, and Dimetrodon vertebrae.  This group has shown that not only is there no compelling support for pelycosaur sails acting as solar collectors, but that in many cases the morphology of pelycosaur spines does not mesh with what one would expect if the sails were primarily adapted to absorbing energy.  Very recently, an analysis of the fourth pelycosaur depicted by Zallinger - Ophiacodon, seen in the mural lounging on the riverbank below Sphenacodon - has added another histological datum to the debate.  This study suggests that Ophiacodon produced fibrolamellar bone, fast-growing tissue that is often associated with warm-blooded metabolisms.  It's worth noting that the study is still in peer-review and that the correlation between fibrolamellar bone and endothermy may not always hold true for extinct taxa, but if these findings hold up, they could push the evolution of warm-bloodedness further down the synapsid tree than had been previously suggested.

19 October 2015

The Wide World of Vertebrate Paleontology (Local Edition): Summer 2015

The desmostylian Behemotops (illustration by Carl Buell)
Beatty & Cockburn 2015
Fall has fallen and I'm enjoying the sensation of being able to enjoy autumn without the prospect of months of soul-sappingly cold weather on the horizon.  To mark the turning of the seasons and to continue my ongoing celebration of being back in the Northwest, let's take a look back at some of the paleontological headlines from this part of the world back when days were longer and temperatures were higher.
  • "Suciasaurus": The story that made the most headlines this summer was the description of a new dinosaur from Sucia Island, the first ever found in Washington.  The specimen consists of part of a femur, which is sufficient to identify it as a theropod, the group that includes all carnivorous dinosaurs and birds.  Beyond this, it's hard to say for certain precisely which type of dinosaur it represents, but the size and age of the specimen make a tyrannosaurid the most likely candidate.  While the specimen was found in the San Juan Islands and described by UW paleontologists, the animal itself probably lived and died much further south, ferried north by tectonic activity.  Exactly how far south?  That depends on your interpretation of the complex tectonic history of the West Coast - likely somewhere equivalent to either Alta or Baja California.
  • Zoneait: A much more impressive specimen of a Mesozoic archosaur was described by Iowa paleontologist Eric Wilberg.  The specimen in question is from central Oregon and is the remains of a thalattosuchian - a seagoing crocodile from the Jurassic.  It's an especially early member of the group, and its age and combination of traits suggest that the evolution of this group of crocodilians was mosaic in nature: adaptations to a marine lifestyle evolved piecemeal rather than all at once.
  • New fossils of Carnivores, Primates, and Desmostylians: Archosaurs are great and all, but the strength of the Northwest vertebrate fossil record is mammal remains, and this summer saw the description of new material for several species.  Some are close relatives of living taxa, such as the ringtail Bassariscus, described for the first time from the Pliocene Ringold Formation by Eric Gustafson.  Others are long-time favorites of mine.  Ekgmowechashala is unusual for so many reasons.  It has a tongue-twisting Lakota name (meaning "Little Cat Man," as the Sioux had no word for monkey). It was the last primate in North America until the arrival of humans around 15 thousand years ago.  Its nearest relatives - and indeed all other primates - disappear from the North American fossil record a good six million years before it appears in the Oligocene of South Dakota and Oregon, begging the question of whether it survived in patches of forest or migrated from Asia.  New material from the John Day Formation, described by a team led by Josh Samuels, muddies the water even further, suggesting that Ekgmowechashala belonged to a primate group known as adapiforms, not to the omomyids, the group to which it had previously been assigned.  Probably the weirdest of the taxa for which new material was described this summer was the desmostylian Behemotops.  Desmostylians were (probably) afrotheres, relatives of elephants and sea cows, that were marine and evolved the thickest tooth enamel of any mammal.  While Behemotops is not a new genus, the new material from Vancouver Island described by Brian Beatty and Thomas Cockburn sheds light on that genus' morphology and on the evolution of desmostylians as a whole.  It also allows the reidentification of existing material from Seal Rock, Oregon as a new genus.  As with many of the taxa discussed in this post (and in keeping with one of my favorite trends in modern paleontology), the new taxon was given a Native American name, in this case Seuku, the name of a trickster from Alsea mythology.
  • Horse Diet Through Time in the John Day: My personal favorite study to be published on regional paleontology this summer was by Kaitlin Maguire, who examined stable isotopes from horse teeth through time in the John Day Basin of Oregon.  These isotopes are valuable tools for reconstructing the diet of herbivorous animals, as they indicate the type of vegetation consumed by an individual.  When analyzed through time, they can show whether or not diet changed within a particular group of organisms.  This is especially interesting when looking at intervals of significant climate change, such as the global warming that characterized the middle of the Miocene Epoch, roughly 16 million years ago.  One might reasonably expect that shifting climate would lead to corresponding shifts in vegetation and in herbivore diet, but the John Day horses examined here do not seem to change their diet across the Middle Miocene.  This may suggest that factors other than climate - such as the delayed arrival in Oregon of particular taxa of grass - have played a large role in driving the evolution of ungulates.

19 August 2015

Fossil Vertebrate of the Month: Mammuthus columbi

The Latah Mammoth looming above other Pleistocene megafauna
The Field Museum
There are many magnificent fossils from the Northwest, from the Cambrian wonders of the Burgess Shale to the Cenozoic animals and plants of the John Day Basin.  Many of these specimens are visually spectacular, quite a few have figured into major debates in paleontology, and all have a fascinating story to tell, but it is unlikely that any have as large an audience as a mammoth uncovered over a century ago outside of Spokane.  The specimen in question was found in a bog on the property of the Coplen Family along Latah Creek in 1876.  Following its excavation, the fossil began an odyssey that has been eloquently described by writer Jack Nisbet.  Along the way, it crossed paths with no less a figure than Thomas Condon, the father of paleontology and geology in the Northwest, and was identified first, incorrectly, as a woolly mammoth and later as a Columbian mammoth, Mammuthus columbi.  In the end, the Latah Mammoth landed in Chicago, where it was owned by the Chicago Academy of Sciences, displayed at the World's Columbian Exhibition, and was finally reposited in the Field Museum.  It remains on display there today, one of the more impressive specimens in one of the world's more impressive fossil collections.  Last year alone, more than a million visitors had an opportunity to view this former resident of the Palouse, making it probably the most visited fossil ever uncovered in the Northwest.  While they were far from the first proboscideans in North America, mammoths were tremendously successful after migrating from Asia at the beginning of the Irvingtonian Land Mammal Age.  Unlike woolly mammoths, which had a holarctic distribution, Columbian mammoths were endemic to North America, and their phenomenal success is attested to by a rich fossil record from the edge of the continental ice sheets to Central America.  While the Latah Mammoth is the most familiar mammoth to have been uncovered from the Northwest, several other fossils of note have been uncovered here that have received varying degrees of scientific and popular attention.  The only specimen to achieve anything near the fame of the Latah Mammoth is the Seattle Mammoth excavated early last year.  The specimen is just a tusk, considerably less impressive on the surface than the Latah skeleton.  However, rather than having been found along a remote creek in eastern Washington, it was uncovered while constructing a new office building in the South Lake Union "neighborhood" of Seattle.  The finding of the remains of so iconic an animal in the midst of one of the fastest-growing parts of a major city and a very successful educational campaign by the Burke Museum have done much to generate enthusiasm for and appreciation of paleontology among Seattleites.  More recently, mammoths were among the animals analyzed as part of an study establishing a chronology of megafauna in the Willamette Valley following the devastation of the Missoula Floods, allowing a more rigorous analysis of the impacts of human activity and climate change than had previously been possible in the region.  Mammoths have long been among the more charismatic of extinct animals, and their popularity was recognized in Olympia in 1998 when a 2nd grade class from Cheney petitioned the state legislature to name Mammuthus columbi the Washington State Fossil, making it an official symbol of the Evergreen State along with apples, hemlocks, and rhododendrons (and, for that matter, petrified wood).

10 July 2015

Fossil Vertebrate of the Month: Bretzia pseudalces

Bretzia pseudalces antlers (on an Odocoileus skull)
From Gustafson (2015)
As I'm returning to blogging and to life as a Washingtonian after a hiatus from both, it seemed appropriate to feature an animal first described from the Evergreen State and that was recently the subject of a monograph in a journal emerging from a long hibernation.  The animal in question is Bretzia pseudalces, a deer uncovered from the Pliocene Ringold Formation of eastern Washington (while other species of Bretzia have been found across western North America, B. pseudalces is known from the Pasco Basin, along the Columbia River north of the Tri-Cities).  The Pliocene age of the Ringold Formation is significant: while deer are abundant across the continent today, they are in fact relatively recent arrivals in North America.  Much as another iconic American animal, the bison, would do in the Pleistocene, deer migrated to the continent only at the very end of the Miocene, just over 5 million years ago (as an aside, of the animals mentioned in 'Home on the Range,' only the pronghorn "antelope" has a deep evolutionary history on the North American plains).  This makes B. pseudalces one of the oldest cervids in North America and part of the first radiation of New World deer.  Superficially, it would have appeared similar to another member of this radiation, the still-extant Odocoileus.  In fact, several features differentiate the two genera, with the most readily apparent of these being the antlers.  While modern white-tailed and mule/black-tailed deer have antlers that are a series of branching tines, the antlers of Bretzia were palmate (that is, shaped like the palm of a cupped hand, as in modern moose).  Precisely how Bretzia was related to other deer remains unclear, though hopefully this will change with future research; an assessment of how the genus fits into the broader picture of cervid evolution could, among other things, help refine our understanding of how immigrant taxa respond to new environments on a large scale, a non-trivial thing in an age during which species are shifting their ranges and being introduced into new environments at unprecedented rates.  Fortunately, the groundwork for such a study has been admirably laid by the University of Oregon's Eric Gustafson, who earlier this year published a monograph on the anatomy and taxonomy of B. pseudalces in Volume 25 of the UO Museum of Natural & Cultural History Bulletin.  This makes the monograph remarkable not only because of Gustafson's scholarly achievement, but because Volume 24 was published in 1983.  Given that the earlier run of the bulletin included such highlights as the description of the saber-toothed salmon and a number of papers by the great Oregon paleontologist and pioneering paleoecologist J. Arnold Shotwell, its reemergence is both exciting and a testament to the vibrancy of paleontology in the Northwest.

25 June 2015


The title of this post means 'Return' in Chinook Jargon, a mix of Native American languages, French, and English that served as the lingua franca of the Northwest from roughly the period of European contact through the end of the 19th Century.  As astute as my readership is, I'm sure you've also noticed that the title of the blog is now in Chinook Jargon as well and that the appearance of the whole page has changed.  Why these changes and why the use of a somewhat obscure language?  Well, just as life, climate, and Earth itself change through time, this blog has evolved since first being founded.  Think of its first iteration, The Oregon Trail, as its Paleozoic, a long interval during which it looked fairly different from its current form but that laid the foundation for what has come since.  The real Paleozoic, of course, ended with Permian Extinction, in turn ushering in the Mesozoic; the epochal event in this blog's history was my move to Cornell College, marking its change to The Mammoth Prairie.  The sudden end of the Mesozoic was marked (and probably caused) by a bolide impact; the similarly unexpected event in my life was a change of scenery from Iowa to Gonzaga University in Spokane.  This has ushered in the third stage in the history of my blog, and just as the Cenozoic is the most interesting period of Earth history, I trust the current iteration of my blog will reach new heights over the coming months.  So much for all the changes and for my recent hiatus; so why all the Chinook Jargon?  In part, because I was returning to the Northwest, I wanted something in keeping with the region's history.  While I've lived a good portion of my life west of the Cascades, my research and current job are both centered in the dryer country to the east, so I wanted to pick something with relevance to both the Pacific and Inland Northwest.  At its peak, Chinook Jargon was spoken widely from the Rockies to the Pacific and from Alaska to the "State" of Jefferson, nicely approximating the boundaries of the Great Northwest.  Beyond simply being locally relevant, though, my choice of a Chinook Jargon name reflects a subtle shift in my goal for this blog.  As the insidious spread of climate change denialism and creationism attest, public understanding of natural science are at or near an all time low.  I and other paleontologists have long viewed our field as a "gateway science" to biology, geology, and even climatology, but in an age where science - at least in the US - is effectively under attack, our role as scientific ambassadors has become increasingly important.  In light of this, my career has drifted more and more towards education and I intend for this blog to follow suit.  Just as I still conduct research of my own, I'll still be posting Fossil Vertebrates of the Month and sharing my thoughts on recent publications from time to time, but there are many other blogs out there that do so more frequently, more eloquently, and with more authority than mine.  I hope that as a research scientist writing about education and fostering appreciation for the natural sciences I will be filling a niche that is less populated and very important.  Just as I hope that this blog will serve as a useful resource for those who want to establish a dialog between scientists and non-scientists, Chinook Jargon was a language that (probably) first developed to facilitate discourse between the multilingual nations of the Northwest and later evolved to allow communication between these nations and European interlopers, making it an appropriate choice for naming this blog.
After all this, though, you may still be wondering what the new title means.  As a trade language, words such as 'paleontology' and 'fossil' are unsurprisingly absent from Chinook Jargon.  However, there is a word for knowing or understanding (kumtuks) and a word for yesterday (tahlkie); put them together and you get "understanding yesterday" (or, if you want to play fast and loose with translation, "understanding the past"), a phrase that not only sums up the goal of my research, but describes what I aim to foster through education.  It's also a nod to a quote from Confucius that's one of my favorites because it so succinctly makes the case for why we should care about paleontology and other historical sciences: "Study the past if you would define the future."

13 March 2015

Delayed Discourse on Diplodocine Discontinuation

Dippy the Diplodocus
The Natural History Museum
It's been another cold, dark winter both literally and, as far as this blog is concerned, figuratively.  I've just returned to Iowa following Cornell's Spring Break and as the snow is melting, the flowers are sprouting, and the weather is warming, I thought it was high time to wake the Mammoth Prairie from its hibernation.
While the winter has been a quiet one in regards to my writing (or at least my writing here; there's been plenty of application and manuscript prep), as per usual paleontology has been making headlines.  There's not much in addressing most of these after the fact, but there was one story that hit a nerve both personally and professionally that I felt was worth revisiting.  I'm betting that the majority of what's left of my audience knows that back in January London's Natural History Museum announced that Dippy, the Diplodocus skeleton that's been the centerpiece of their main hall for nearly four decades is going to be replaced by a blue whale skeleton as part of the museum's renovation project.  I've written before about the personal significance of Dippy to my own development as a paleontologist (the brief synopsis is that he was the key figure in my origin story) and so, like a whole generation of paleontologists, my first reaction was one of dismay.  However, approaching things from a museological standpoint, it's not too hard to come up with a whole list of reasons why a blue whale makes for a better centerpiece.  It's bigger, first of all; bigger, in fact, than any dinosaur or any other vertebrate that has ever lived (unless you buy the upper limits of the mass estimates for some sauropod species, of which it is wise to be extremely skeptical given the scrappiness of the material and the corresponding degree of extrapolation necessary in most cases).  This may sound trivial, but the NHM's central hall was clearly envisioned by its founder Richard Owen and architect Alfred Waterhouse to evoke the style of Europe's great cathedrals, and it has stood the test of time as one of the most spectacular examples of monumental museum architecture in the world.  Diplodocus was undeniably a big animal, but was quite svelte for its size, meaning that Dippy has always been dwarfed by his surroundings; architectural sketches seem to suggest that the whale will fill the space better.  Also, Dippy hails from Wyoming, while the blue whale was found beached in Ireland, meaning that while the star of the museum's show still won't be English, it will at least be from the British Isles.  Dippy, for all his fame, is a cast of a specimen housed in Pittsburgh, while the whale will be the genuine article.  Even the argument that Dippy should be retained because he is the museum's traditional centerpiece don't hold water, as a whale skeleton occupied the space well before the dinosaur made its debut.  And so, despite my personal attachment to Dippy, from pretty much practical and educational standpoint, the whale makes much more sense.
Illustration of the NHM Blue Whale
The Natural History Museum
Professionally, though, there is one aspect of the NHM's plans that troubles me more than it probably should.  The museum has stated that part of its motivation for bringing in the blue whale is to emphasize their focus on the ecology and conservation of modern ecosystems.  Without a doubt, studying and mitigating the impacts of human activity on the natural world is the most important goal of natural science, and in that sense the museum's motivation is laudable.  However, it doesn't necessarily follow that an emphasis on ecology and conservation should displace displays of fossils.  Paleontology suffers from a widespread and misguided perception of obsolescence.  The word dinosaur has, after all (and, again, misguidedly), come to mean something outmoded and inferior and even recently extinct organisms have come to be synonymous with being outdated (see 'gone the way of the dodo').  I don't for a moment suppose that the exhibit designers involved have an anti-paleontology agenda, nor does the displacement of one dinosaur by one whale mean that one of the world's largest fossil repositories will be subbing in pandas, insects, and sea turtles for their ground sloths, ammonites, and plesiosaurs.  However, one cannot help but worry that this will only help reinforce the artificial line between "practical" neobiology and "impractical" paleobiology when in fact, paleontology is (or at least should be) an integral part of ecology, evolutionary biology, and even conservation biology.  I could selfishly point to a paper on which I was a co-author that came out during my blogging hiatus that shows how important paleoecology can be in formulating and testing models of the effects of future environmental change, but for the sake of argument lets stick to whales.  Cetacean paleobiology is a flourishing branch of paleontology, and with good reason.  Between heavy bones, wide distributions, and living in a top-notch preservational environment, whales have a magnificent fossil record that, more clearly than in any other organism, tracks the evolution of land-living animals into marine taxa.  This is most famously illustrated by Phil Gingerich's work on Eocene cetaceans from Pakistan and Egypt, where a spectrum of fossils lying between fully terrestrial cetaceans to seagoing whales with vestigial hind legs have been found.  Elsewhere in the world (my Northwest pride compels me to note that this encompasses the Washington and Oregon coasts) other major transitions, such as the evolution of baleen or the bizarre morphology of river dolphins, are clearly documented by cetacean fossils.  Just as fossils demonstrate how whales have evolved, so too do they reveal how whales have shaped and been shaped by the organisms and environments with which they interact.  Whale paleocology is perhaps best illustrated by the study of whale fall communities, long one of the most important deep-sea ecosystems.  This field of study has yielded myriad papers by researchers from across the globe, one of which (Pyenson & Haasl 2007) is one of the neatest examples out there of how ecology profits when both paleoecological and neoecological data are considered.  So how is this exceptional fossil record relevant to whales now and in the future?  First of all, it shows us how the diversity and ecology of modern whales came to be, putting modern forms in their proper evolutionary context.  Beyond this, understanding when and in which groups major evolutionary or ecological changes occurred allows us to approach the question of which forces have driven whale diversification and extinction and how these changes have affected other organisms, a field of study that has been most prominently (but by no means exclusively) explored by Ewan Fordyce.  Understanding the forces that have shaped whale evolution, particularly during periods of time that differ climatically from today, could in turn play a huge role in predicting the effects that warming oceans, fluctuating food supplies, and interactions with human activity may have on whales and on the organisms and environments with which they interact.  A blue whale, then, is a fantastic choice for conveying the magnificence and precariousness of life on Earth today, but is also just one player in a vast evolutionary saga that can only be fully told by including fossil data.  Put in the proper context, the NHM blue whale could become the world's most prominent illustration of how the big questions about life on Earth both today and in the future are best answered by integrative science that incorporates data from neontologists, paleontologists, climatologists, geologists, and many, many others.  Displayed out of context, it could further reinforce the harmful impression that science operates within compartmentalized disciplines, some of which are more "valuable" than others.  Here's hoping they do the right thing.

03 July 2014

Fossil (Gondwanan) Vertebrate(s) of the Month: Palorchestes & Diprotodon

'Giant Kangaroos & Wombats' by Charles R. Knight
Field Museum of Natural History
When the great paleoartist Charles R. Knight painted the mural at left in the 1920s, he thought he was depicting two unrelated marsupials from the Pleistocene of Australia.  Certainly the two animals would have been familiar to Knight's audience of natural history dilettantes at Chicago's Field Museum; they were among the first fossils ever to be described from Australia - by no less a luminary than Sir Richard Owen - and had become icons of Victorian paleontology.  This is particularly true of Diprotodon, the animal lumbering into view on the right hand side of the mural, which remains one of the most familiar members of the Australian megafauna.  Diprotodon is often referred to as a giant wombat, which is not too far from the truth, as its closest (though still somewhat distant) living relatives are koalas and wombats, and it certainly was a behemoth.  In fact, at around the same size as a large rhinoceros, it was the largest marsupial ever to have lived.  When Owen described Palorchestes 1873, it seemed like a similarly superlative animal: a giant kangaroo, hence its genus name, meaning 'Ancient Leaper' and its appearance in Knight's mural.  Owen was the greatest comparative anatomist of his day and once famously reconstructed the appearance of a moa on the basis of a single bone, but even the best get it wrong sometimes.  It took nearly a century, but in 1958 the Australian paleontologist Jack Woods recognized that the teeth of Palorchestes indicated that it was not, in fact, a kangaroo, but a fairly close relative of Diprotodon.  If an ancient Australia without giant kangaroos seems dull, don't fret: there WERE truly enormous kangaroos in the Pleistocene, and subsequent discoveries have shown that Palorchestes was even weirder than first thought.  The structure of its nasals suggests that the skull supported a tapir-like trunk to go along with its tapir-like teeth, though its elongated, powerful forelimbs, large claws, and grooved lower jaw apparently indicative of a long, flexible tongue impart an appearance that defies comparison to any living mammal (the closest comparisons that spring to mind are extinct ground sloths and chalicotheres).  Incidentally, palorchestid and diprotodontid fossils are often found near billabongs and other bodies of fresh water (possibly due to congregation and mass mortality during droughts), and it's been suggested that their fossils gave rise to the bunyip legend and thus, indirectly, the greatest childrens' book of all time.