Fossil Vertebrate of the Month: Diceratherium

Diceratherium
John Day Fossil Beds National Monument

This is the last FVOTM I'll be publishing in Oregon, so I thought I'd focus it on the most impressive fossil vertebrate I've found during my time in that state (I would have put the spotlight on Metasequoia, the state fossil, but as a plant it falls outside the scope of a feature on fossil vertebrates).  In the summer of 2010, I was TA-ing the UO Geology Department's field camp in eastern Oregon.  We were prospecting for fossils in the gullies of the Turtle Cove Member of the John Day Formation when I almost literally stumbled across what turned out to be a tibia of the rhinoceros Diceratherium.  One of the things I've discovered during my time here is that I have a terrible eye for fossils in the field, which made finding a rhino leg fairly exciting for me.  However, this excitement was tempered by the fact that Diceratherium was an extremely common member of the John Day ecosystem.  This may come as something of a surprise to many people, as rhinos are, of course, not members of the North American megafauna today.  However, the oldest fossil rhinos are from the Eocene of North America.  The two-horned Diceratherium first appeared in the Oligocene, a period of time during which rhinos had begun to spread across the world.  Diceratherium was an especially successful disperser, having spread into Asia and Europe by the Miocene.  By the Pliocene, rhinos had disappeared from North America, and they survive today only in the Old World.  There are a number of unusual features of rhinos, including their horns and broad teeth, but perhaps one of the strangest things about them is a product of their evolutionary history.  The earliest rhinos were small, running animals; enormous size did not evolve until later in the group's history, but even the very large rhinos of today still run frequently (charging being one of their main forms of defense and intimidation).  The stress this puts on their legs is enormous, and as a result most adult rhinos have arthritis.  Research by former UO undergrad Kelsey Stilson has shown that this trend extends far back into rhino evolution and would have occurred even in mid-sized members of the group such as Diceratherium.

Fossil Vertebrate of the Month: Tylosaurus ivoensis

Tylosaurus. ivoensis and other marine vertebrates from the Karlstad Basin (Sørensen et al 2013)

Many of you may be familiar with my long-standing love of all things Swedish as well as my more recent interest in Denmark (born out of a couple of trips to Copenhagen and the discovery that I am distantly related to the Danish Vikings that invaded Ireland).  Both countries celebrate their national holidays in June (Denmark on the 5th, Sweden on the 6th) and Midsummer, a major holiday throughout the Nordic countries, occurs late in the month, so I thought I'd revel in my Scandinavophilia (Scandinaviophilia?  Scandinaviaphilia?) by highlighting one of the more spectacular fossil vertebrates to have been discovered in Skåne, the historically Danish region of southern Sweden.  During the Late Cretaceous, sea levels worldwide were extremely high, flooding low-lying areas of land, including most of Europe and what are now the Great Plains of North America.  These shallow seas were home to organisms ranging from the plankton whose shells would eventually form the chalk beds that gave the Cretaceous its name (and the White Cliffs of Dover their characteristic color) to the first marine birds to fish of all shapes and sizes to large marine reptiles.  Remains of such reptiles are especially common in the Kristianstad Basin of Skåne, and in particular along the shores of Ivösjön, one of the large lakes dotting the landscape of southern Sweden.  Reptiles recovered from the area include crocodiles, turtles, plesiosaurs, and mosasaurs, relatives of snakes and monitor lizards and the group to which Tylosaurus ivoensis belongs.  Mosasaurs are by no means unusual in the fossil record of northern Europe, but they have an especially rich fossil record in the Kristianstad Basin.  The seas of Skåne played host to a complex food web (as demonstrated by a study published just last month) and while smaller mosasaurs likely preyed upon fish and ammonites, there is direct evidence that large species such as T. ivoensis fed on other marine reptiles.  Mosasaurs, of course, are absent from the world's oceans today, and marine rocks from Scandinavia give some indication as to why.  Not all extraterrestrial impacts are associated with widespread extinctions, as the fantastically-named Mjølnir Crater of Norway shows, but an impact at the end of the Cretaceous seems to have played a major role in sealing the fate of many animals, including mosasaurs.  Early evidence for this impact also came from Scandinavia: the cliffs of Stevns Klint, a Danish site south of Copenhagen, were among the localities studied by Walter Alvarez when he first proposed his now-famous impact hypothesis.

The Mammoth Prairie

Mammoths & Sabertooth Cats (Zdenek Burian)

For several years now, I have been based in Oregon, first as a grad student and then as an instructor.  This blog, originally intended as a way of staying in touch with friends in family in a pre-Facebook age and subsequently evolving into a sounding board for my thoughts on paleontology, has always been written from an Oregonian perspective (hence its name).  However, I was fortunate enough to get a postdoc at Cornell College in Iowa, where I will be moving later this year.  I have only just started getting back into blogging and it's something I want to not only continue, but to do more of.  I intend to keep this site going, and at this same URL, but as Iowa is a long way from Eugene or Roseburg and since the Oregon Trail began one state to the south of where I'll be, the current title of this blog will clearly need to be changed.  I'm currently leaning towards 'The Mammoth Prairie" as a tip of the cap to the mammoth fossils uncovered near where I'll be living (and in recognition of the fact that mammoths and mastodons are likely to become a stronger focus of my research over the next few years) as well as to the tallgrass prairie ecosystem that historically covered most of Iowa.  I also like the name because it has echoes of the 'mammoth steppe,' the name coined to describe the dry tundra environment of Arctic North America and Eurasia during the Pleistocene and a phrase that I've always found highly atmospheric.  Before I make the change, though, I thought I'd field thoughts on the name and alternative suggestions from whatever is left of my reading audience, so let me know what you think.

Bellingham's Big Bird

DiatrymaUniversity of Wyoming Geological Museum

Note: I wrote this post some time ago when this was actually breaking news. It no longer is, but at Edward Davis' urging, I'm trying to get back into active blogging, and I thought I'd begin by finally posting this.  Bona fide new posts to follow.  Eventually.

The western half of the Northwest is, for the most part, a geologically young landscape, shaped by the still-growing Cascades and by sediments deposited during the Pleistocene.  The fossils found here are, for the most part, correspondingly young.  In the Puget Sound Lowlands and the Willamette Valley in particular the vertebrate fossil record is dominated by Ice Age mammals (including the Manis Mastodon).  However, there are pockets of older rocks in the region, including the Oligo-Miocene formations of the outer coast that have yielded some of the world's most important specimens of marine mammals and the marine reptile-bearing Cretaceous rocks along the Strait of Georgia.  Among the most unusual vertebrate fossils in the region are those from the Chuckanut Formation near Bellingham.  In the Eocene, the area was a low-lying floodplain in a warm climate (as indicated by the palm fronds that have been found there).  Bones of fossil vertebrates are rare in the formation, but many animals left their footprints in the then-soft sediments of the floodplain, several of which have been preserved as fossil trackways.  Trackways and other trace fossils are invaluable paleoecological tools, as they preserve direct evidence of interactions between organisms and their environment.  A recent publication out of Western Washington University describing a pair of giant bird tracks from the Chuckanut Formation is a nice case study of the use of fossil footprints in making inferences about the behavior of extinct animals.  One of the Eocene's most charismatic animals was the giant flightless bird Diatryma (possibly the same animal as the European Gastornis of BBC fame).  Diatryma bones are well-known from the Eocene beds of Wyoming, and when it was first discovered by Edward Drinker Cope in the late 19th Century, it was thought to be a carnivore and was frequently depicted as preying upon the small horses that were common in the area.  However, it has subsequently been hypothesized that Diatryma was herbivorous, possibly using its large beak to crack nuts or fruit rinds.  The Washington tracks have been tentatively assigned to Diatryma or a close relative; while assigning trace fossils to a taxon previously known from body fossils always entails some risk, but since no other large birds are known from the Eocene of North America, in this case the authors are not going out on too much of a limb.  If the tracks were indeed made by Diatryma, they provide some hints as to the animal's behavior, as they don't seem to show any evidence of the sharp talons that characterize modern predatory birds (including, significantly, the terrestrial secretary bird).  This is not, of course, the final word in the debate; it's entirely possible that if Diatryma were a predator, it relied more on its beak than its feet for hunting, and it's not outside of the realm of possibility that evidence of talons simply wasn't preserved in these tracks.  However, the footprints do provide a novel viewpoint, and it is certainly to be hoped that the Chuckanut Formation will continue to produce fossils that will help elucidate the ecology of Eocene ecosystems.

Fossil Vertebrate of the Month: Rutiodon carolinensis

At the end of last month, I spent a week out East, visiting the collections at the American Museum of Natural History and in Chapel Hill at a workshop that I would recommend to any geologists out there that are in the late stages of a PhD or the early stages of a postdoc.  While the two states have followed very different historical trajectories, to vertebrate paleontologists New York and North Carolina have one big thing in common.  The Newark Supergroup is a series of Late Triassic and Early Jurassic formations that run from Nova Scotia to the Carolinas; representing a wet, seasonal rift valley environment, these rocks are among the best places in the world to find fossils from early in the "Age of Dinosaurs" (and certainly the best in North America outside of the red beds of the Southwest).  Pictured above is perhaps the most iconic fossil from the Newark Supergroup, the phytosaur Rutiodon carolinensis.  Any student that's ever taken a class from me will be familiar with phytosaurs, which are one of my favorite examples of convergent evolution.  Superficially, members of this now-extinct group were very similar to modern crocodiles and doubtless filled a similar ecological niche (piscivores/ambush predators).  However, several features of the skeleton show that they are not the direct ancestors of crocodiles (which, in the Triassic, were primarily small, agile, and land-living); the most notable of these is the placement of the nostrils above the eyes rather than at the end of the snout as is the case in alligators and crocodiles.  The specimen pictured above is a historically significant one.  As the species name suggests, the first Rutiodon specimens to be uncovered were found in North Carolina.  One of these specimens, from a coal mine near the town of Egypt, was acquired by W.D. Matthew in 1895.  He brought it back to New York, where it became the first vertebrate fossil in the collection of the American Museum of Natural History (it bears the specimen number AMNH 1), which in the subsequent decades would grow to become the largest collection of fossil vertebrates in the world.

Fossil Vertebrate of the Month: Panthera atrox

P. atrox in the Natural History Museum of L.A. County
John Orcutt, 2010

At least in Oregon, this March has certainly come in like a lion, which inspired this month's FVOTM: Panthera atrox, the American lion.  There has recently been some debate over whether or not this common name is correct: while very lion-like, Per Christiansen and John Harris have suggested that it was actually more closely related to jaguars.  I come down on the other side of the debate: the morphological data are, at best, ambiguous (and I would argue that they tend to favor the interpretation of P. atrox as a true lion) and molecular data from subfossil specimens indicate that P. atrox was very closely related to both modern lions and to European cave lions (in fact, some have argued that all three species really should be lumped into one).  Panthera atrox is best known from the "tar" seeps of Rancho La Brea, where it is the most common conical-toothed cat (though not the most common cat; that honor goes to the saber-toothed Smilodon).  Because it is less common than its machairodontine "cousin," it has been suggested that, unlike modern lions, P. atrox might have been solitary; this should come as no surprise as modern lions are very unusual among cats in living in large social groups.  Panthera atrox certainly would have been large enough to tackle prey on its own.  In fact, with the largest individuals weighing in at somewhere around 350-400 kg, it was probably the largest conical-toothed cat ever, and would have been in the same size range as the largest saber-tooths (as well as a few species of bear).

Fossil Vertebrate of the Month: Nothrotheriops

Nothrotheriops in the Nevada State Museum, Las Vegas
John Orcutt, 2011

Sloths have figured prominently on this blog lately (see my posts on Megatherium and Megalonyx from the past year).  That theme continues this month with Nothrotheriops, a genus of ground sloth that has been found throughout the southwest US and northern Mexico (and at one site in Florida), including within the Phoenix metro area, site of this month's Western Association of Vertebrate Paleontologists annual meeting.  There are two known species: N. texanus and its apparent descendant N. shastensis, both of which lived during the Pleistocene.  While my previous sloth posts have focused primarily on the taxon's place in the history of science, Nothrotheriops is remarkable as an example of how paleontological data can inform our knowledge of both paleo- and modern ecology.  This is in large part because it lived primarily in arid climates and apparently frequented caves, possibly even using them as sites for dens, meaning that Nothrotheriops has a fantastically high preservation potential and that preserved soft tissue and dung are not uncommon.  Analysis of the dung has been particularly informative, providing direct evidence of the plants eaten by the sloth (primarily desert globemallow) as well as of interactions with other organisms (fungus gnat larvae fed on vegetable matter in the dung, which also contains traces of parasitic nematodes).  Perhaps the most remarkable aspect of Nothrotheriops ecology, though, is its connection to Joshua trees.  Despite being icons of the Mojave Desert, Joshua trees may be doomed to extinction (or at least widespread local extirpation) due to their extremely slow dispersal rate keeping them from shifting their range in response to climate change.  Based on relatively large amounts of Joshua tree material having been found in Nothrotheriops dung, it is not unreasonable to assume that the sloths, in eating and excreting seeds, served as important dispersal agents for the trees.  A recent paper has suggested that the extinction of sloths and other desert megafauna made the Joshua tree an effectively immobile species.  While this hypothesis awaits a rigorous paleontological test, if it proves to be correct (as seems very likely) it will have important implications for the conservation of Joshua trees, underscoring the importance of fossil data in predicting and mitigating the effects of future climatic change.

Fossil Vertebrate of the Month - Lystrosaurus

One hundred years ago this month - on January 6th, 1912 - Alfred Wegener presented his idea that the continents had once all been joined (in a supercontinent he termed Pangaea) and were slowly floating apart as part of a process he called continental drift.  His hypothesis was largely derided at the time, but would eventually evolve into plate tectonics, which is now the unifying theory of geology.  Numerous lines of evidence were brought together to establish the validity of plate tectonics, but among the most convincing was the presence of remarkably similar fossils on distant continents.  Perhaps the most famous of these organisms was the Permo-Triassic dicynodont Lystrosaurus.  First described from South Africa, the discovery of Lystrosaurus fossils in Antarctica in the 1960s showed beyond a reasonable doubt that the two continents must have been joined (it has subsequently been uncovered in India, East Asia, and Europe, driving home the reality of plate tectonics even further).  Besides its utility as a biogeographic marker, Lystrosaurus is remarkable for being one of the few survivors of the Permian-Triassic Extinction, which, by some estimates, wiped out over 90% of life on Earth.  Why it was able to survive this cataclysm and to prosper in its aftermath is something of a mystery, as in many ways Lystrosaurus is a very unimpressive animal (they are often referred to as the pigs of the Triassic).  In fact, my original dissertation project (before I was romanced by its distant mammalian relatives) was to be a test of the hypothesis that Lystrosaurus, as a burrowing animal, was adapted to the low-oxygen conditions that may have characterized the Early Triassic.  In another Oregon-related note, the picture above is of a model from Prehistoric Gardens, south of Coos Bay, one of the more atmospheric and well-preserved "dinosaur parks" in the world.

Fossil Vertebrate of the Month: Shonisaurus popularis

Earlier this month, the Society of Vertebrate Paleontology held its annual meeting in Las Vegas.  The conference logo - one of the best I've ever seen for an SVP meeting - featured the ichthyosaur Shonisaurus, Nevada's state fossil (shown in the picture at left in the new Nevada State Museum, Las Vegas).  Shonisaurus was a remarkable animal.  Dating from the Late Triassic, it was not only one of the earliest ichthyosaurs, but at 15 meters in length was also among the biggest (the largest known ichthyosaur was the Triassic Shastasaurus, which has been reported from Oregon, British Columbia, and Northern California, among other places).  Shonisaurus skeletons have been found in large numbers - and in remarkably good condition - in Berlin-Ichthyosaur State Park southeast of Reno, making it among the best-known early ichthyosaurs.  The concentration of skeletons at the locality has been interpreted several different ways through the years.  It was originally thought to represent a stranding site, but the lithology and paleontology of the site indicate a deep water environment.  It has also been interpreted as evidence of an ichthyosaur breeding ground, though the lack of juvenile specimens contradicts this hypothesis.  The generally accepted explanation for the bone bed is that it represents an area of upwelling that would have brought nutrients up from the deep sea, supporting a diverse ecosystem in which Shonisaurus would have been the top predator.  Unfortunately, Shonisaurus has also been the subject of an exceptionally high-profile and exceptionally shoddy study this year that used the arrangement of skeletons as "evidence" of an exceptionally intelligent cephalopod; the readiness with which a talk on the subject was accepted by the Geological Society of America and the eagerness with which it was reported by the media are black eyes for paleontology and for scientific journalism.

The Manis Mastodon

While growing up in Seattle, I often lamented the lack of dinosaurs from the Pacific Northwest, but I always took some solace in the fact that we had some pretty cool mammal fossils.  I was a regular visitor to the Burke Museum to see the Blue Lake Rhino and the Sea-Tac Sloth, and my family indulged me enough to take me on trips to Ginkgo State Park, Republic, and the John Day Fossil Beds.  One of my particular favorite Northwest fossils was the Manis Mastodon, found near the town of Sequim, on the Olympic Peninsula, because, as a proboscidean, it was big, and therefore akin to the dinosaurs I so desperately wanted to study.  Now, of course, things have come full circle, and I'm living in the Northwest again and studying mammal paleontology.  I have a new appreciation for all the fossils I visited as a child (the John Day fauna has, in fact, become a huge part of my research), and it turns out that one of my old favorites was even more important than I realized.  The Manis Mastodon wasn't just big: it turns out that it's one of the only specimens in North America that preserves evidence of humans butchering a mastodon.  It had long been suspected (at least by some) that a bone point embedded in one of the mastodon's ribs was a broken-off projectile point, which would imply that humans not only scavenged mastodon carcasses, but might have actively hunted them as well.  This hypothesis was recently put to the test by a group of researchers that includes WSU's Carl Gustafson, the scientist that conducted the initial study of the site.  Scans of the rib confirm this hypothesis, but perhaps the most exciting finding of the study was that the Manis site was far older than had been expected: about 13,800 years old.  This revelation has two major implications.  First, it supports the evidence of the so-called "Kelp Highway" hypothesis (the main research focus of Oregon's own Jon Erlandson) that humans populated the Americas by travelling south along the West Coast.  Second, it suggests that humans were hunting large animals prior to the development of stone Clovis points, which may itself have implications for the extinction of the North American megafauna.  The moral of this story?  Never let anyone (even a younger version of me) tell you that there aren't any interesting fossils in the Northwest; as long as our region continues to yield finds like the Manis Mastodon, there will be plenty to keep paleontologists here busy for a long time.

Addendum: Adding to the Manis Mastodon's Northwest cred, Knute Berger, my favorite Seattle journalist has supplied a brief article on the subject.

Fossil Vertebrate of the Month - Terror Bird

This is the largest group of organisms I've ever featured as a FVOTM, but given that we're coming up on Halloween, it seemed appropriate to spotlight a family whose common name is based on how terrifying they were.  Terror birds (or, more correctly, phorusrhacids), represented by the LA County Museum's mount of Paraphysornis in the picture at left, were a group of giant, flightless birds related to living seriemas, most of which have been uncovered in South America.  Flightless birds are not unusual, as anyone who's seen an ostrich, emu, or rhea (or fossils of elephant birds, moas, or mihirungs) can attest.  However, phorusrhacids were different in one key respect: they were carnivorous.  Carnivory has been suggested for some other land birds - chief among them the Eocene Gastornis, itself a possible terror bird ancestor - but the huge size, robust build, and raptor-like beaks of phorusrhacids leave no doubt.  In fact, the near absence of large mammalian carnivores in South America for most of the Cenozoic indicates that the top predator niche on that continent was occupied by terror birds (they would have preyed upon one of the strangest herbivore faunas in the world, composed of, among other things, meridiungulates, xenarthrans, and - somewhat inexplicably - platyrrhine primates and hystricomorph rodents).  Phorusrhacids were key players in the American Biotic Interchange; once thought to have gone extinct when mammalian carnivores (including the iconic Smilodon) moved in from the north, it is now known that terror birds actually expanded onto the Gulf Coastal Plain in North America, where they were represented by Titanis, one of the largest birds ever to have lived (though it was not the largest phorusrhacid - that honor is currently bestowed on the recently-described Kelenken from Argentina).

Fossil Vertebrate of the Month: Megalonyx jeffersoni

This month's (somewhat belated) fossil vertebrate is a long-time favorite of mine: Megalonyx jeffersoni, a Pleistocene ground sloth.  The reasons for it being one of my favorites are prosaic enough: there was a skeleton of one in Seattle's Burke Museum while I was growing up (a specimen that was discovered during the construction of Sea-Tac Airport, which I always felt would make it a good candidate for Washington State Fossil, an honor that's since been bestowed on the Columbian mammoth).  Ground sloths are one of the great evolutionary success stories to come out of South America, having been among the first animals from the formerly island continent to expand into North America after the formation of the Isthmus of Panama about 3 million years ago (ground sloths actually seem to have made the jump to North America well before the isthmus was fully formed, suggesting that they, like modern sloths, were very capable swimmers).  Ground sloths thrived in North America until the Pleistocene megafaunal extinction, around 13,000 years ago, that also sounded the death knell for mammoths, horses, camels, and many other types of mammal on the continent.  Megalonyx has the distinction of being the only fossil vertebrate to have been described by a President of the United States: Thomas Jefferson, who described a specimen from a cave in West Virginia as a kind of lion.  The great anatomist Caspar Wistar subsequently reidentified it as a sloth, named the species after the then ex-president, and is thought to have suggested to Meriwether Lewis that he keep a weather eye open for living megafauna, such as Megalonyx, during his expedition west with William Clark.

Orcutt & Hopkins, 2011

It's been a long time coming, but as of today, my first paper is officially published.  It's in this month's Journal of Vertebrate Paleontology and has the thrilling title 'The canid fauna of the Juntura Formation (Late Clarendonian), Oregon.'  It's far from groundbreaking work, as most of it is a redescription of misidentified specimens, but it does have its noteworthy elements.  It includes the description of a jaw of the giant dog Epicyon saevus found during our lab's field work in 2008.  It provides information on the postcrania of the even more giant E. haydeni and the much smaller (but previously unknown from the Northwest) Carpocyon.  Perhaps most importantly, it's the first publication to come out of the Hopkins Lab's Juntura Project.  The Juntura Basin east of Burns in southeast Oregon was the research focus of the pioneering paleoecologist J. Arnold Shotwell (also of the U of O) until the 1970s, but has been largely neglected since Shotwell left the field.  Our lab's field work in the area has been the first concerted research project there in nearly forty years, and if nothing else my paper stands as the first fruits of what will hopefully (and presumably) be a very fruitful paleontological endeavor.

Fossil Vertebrate of the Month: Archaeotherium

It's springtime, which means its time for class field trips, which to a paleontologist in Oregon can only mean it's time to head to the John Day Basin.  The fossil beds of the John Day country are some of the best continuous exposures of Oligo-Miocene sediments in the world, and have yielded everything from tiny "worm-lizards" to gomphotheres.  One of my favorite animals from the area, though, is the entelodont Archaeotherium from the Late Oligocene Turtle Cove Member of the John Day Formation (in the picture at left, Archaeotherium can be seen in the foreground, while the background is Sheep Rock, the most spectacular of the Turtle Cove outcrops).  Entelodonts have been popularly termed 'terminator pigs' or 'hell pigs,' and with good reason.  Opinions are split on whether or not entelodonts were particularly closely related to pigs (they may have been closer relatives of hippos), but they certainly would have been hellish things to encounter.  Their large, flat teeth are similar to those of bears, pigs, and humans (though on a much larger scale than the latter two), and like all these animals they were almost certainly omnivorous, making them some of the only artiodactyls to include meat as a major part of their diet.  The skulls of entelodonts, including Archaeotherium, are generally long and characterized by strange protuberances at the back of the jaw that may have served as anchors for muscles or, perhaps more likely, may have played a role in display or competition for mates.  Archaeotherium was a mid-sized entelodont, but members of the family could grow to huge sizes: the giant Daeodon (once known by the fantastic name Dinohyus, or 'Terrible Pig') grew to the size of a rhinoceros.

Fun With Body Mass Estimates

The latest issue of the Journal of Vertebrate Paleontology has been a minor media sensation because it includes a description of the largest known rabbit, Nuralagus rex from the Pliocene of Menorca (as neat an illustration of the Island Rule as ever there was).  For those of us interested in carnivores, though, the issue also included the description of, as the authors put it, 'a gigantic otter.'  The otter is from the Pliocene Awash region of Ethiopia - site of many a famous hominid discovery - and is a new species in the genus Enhydriodon: E. dikikae.  Giant animals are always fun to read about, and they're even more so to someone writing a dissertation on mammal body size evolution.  The paper includes dental measurements for the new species, including the dimensions of the first lower molar (the carnassial, for those that know your carnivore teeth), which is tightly correlated with body size.  I couldn't resist plugging the E. dikikae measurements into the body mass regression for mustelids developed by Blaire Van Valkenburgh to get some kind of idea of the size of the animal.  There are two specimens included in the paper: the smaller, more complete tooth suggests a 77 kg animal, while the larger, incomplete tooth may represent an animal of 126 kg.  The former mass would put the individual in the same size range as modern giant otter (Pteroneura brasiliensis), but the larger individual would be in a class by itself; a 126 kg otter would be roughly the same size as a large jaguar or a small lion.  Of course, as with any body mass estimate for exceptionally large (or small) animals, these numbers should be taken with a grain of salt: the very fact that E. dikikae is so big means that it falls well outside the range of masses in living mustelids (with the not insignificant exception of the giant otter) and that any estimate of its weight is therefore extrapolating beyond the available data (the same issue has been raised for mass estimates of giant South American rodents).  Still, it's fossils like this that remind me why I consider myself lucky to be a paleobiologist; after all, what other field would publish journals describing giant rabbits and otters in the same issue?  Life, and in particular prehistoric life, is just so cool.

Fossil Vertebrate of the Month: Baryonyx walkeri

Last month's fossil vertebrate was an Irish icon, so in honor of April's St. George's Day, it only seems fair to put the spotlight on an English animal.  The earliest dinosaurs to ever be described were English, but for the most part the end of the Victorian Era was also the end of new dinosaur discoveries in Great Britain.  A few new taxa have come to light in the previous few decades, though, perhaps the most impressive of which is the bizarre Baryonyx walkeri.  Uncovered in Surrey in 1983 and named in 1986, the genus name translates as 'heavy claw,' a reference to the large, recurved claws on the animal's hands.  The other noteworthy feature of Baryonyx is its elongated skull with a kinked jaw, remarkably similar to that of a crocodile.  This skull, in conjunction with fish scales found within the specimen's body cavity, led to the conclusion (since challenged by some, but still largely accepted) that Baryonyx was piscivorous.  It's unusual morphology meant that the relationship of Baryonyx to other dinosaurs remained a mystery for some years, though the discovery of similar dinosaurs have shown that it was a member of the Spinosauridae, a group of large (in at least one case very large), sometimes sail-backed, likely fish-eating group of theropods that lived mainly on the southern continents during the Cretaceous.  Baryonyx was very closely related to the much-publicized African spinosaur Suchomimus tenerensis; in fact, the two were likely members of the same genus.

José María Velasco

Serendipity can be a wonderful thing.  While doing research in Mexico City last September, I spent a day in the historic center of the city, and one of the places I visited was the Antiguo Colegio de San Ildefonso; tourists like me flock there because it was the birthplace of the Mexican muralist movement, but while I was there it was also hosting an exhibit celebrating the centennial of the Universidad Nacional Autónoma de México.  You can imagine how pleasantly surprised I was to round a corner in the geology section of the exhibit to see these:

The paintings above, as well as a third of cave bears that I couldn't find an imagine for online, are by the artist José María Velasco, who I have to admit I'd never heard of before my trip.  He lived and worked in the late 19th and early 20th Centuries and is best remembered for his landscapes of the Valley of Mexico, which have served as a touchstone of Mexican national identity.  He was also a scientist, with a particular interest in natural history (a running theme in his profession, it so transpires, as Mexico's greatest landscape artist, Dr. Atl, was also an amateur volcanologist and advocate for science); he even described a species of salamander, that has since been renamed in his honor.  This may explain why he was commissioned to decorate UNAM's Instituto de Geologia.  Velasco's paintings have adorned the palatial building (itself as glorious an example of early 20th Century museum architecture and design as you'll find anywhere in the world) near central Mexico City since the 1910s, and had been brought over to the UNAM exhibit during some renovations (you can get a sense of how they look in situ in this picture).  Information on the paintings is scarce, but it appears that Velasco painted two series: one tracing the history of marine life and one depicting terrestrial animals and landscapes through time.  These would have been painted at roughly the same time as some of the greatest works of Charles R. Knight and his European counterpart, Heinrich Harder, and I would argue that not only are Velasco's reconstructions in the same league as those of his more famous contemporaries (though it must be said that no one before or since can compete with the vibrancy of Knight's animals), but he in fact surpasses them in many ways; his paleo-landscapes are especially impressive (though sadly underrepresented online).  This should come as no surprise, as Velasco was, after all, a classically trained painter and one of his country's greatest artists of the pre-modern era.  It seems a shame that his contributions to scientific illustration and paleoart should have lapsed into obscurity, and I thought I'd do my humble best to try to share some of those contributions with the world.

Brontomerus, Hell Creek, and Mesozoic Ecology

Two dinosaur-related stories have been getting a lot of press this month.  The first is the naming of the new sauropod Brontomerus mcintoshi (Taylor et al. 2011), which is remarkable for its name (literally 'McIntosh's Thunder Thighs'), its oddly large legs, and its implications for Early Cretaceous sauropod diversity.  The story that is more intriguing to me, though, is the publication of the results of the Hell Creek Project dinosaur census (Horner et al. 2011).  For those who aren't familiar with it, the Hell Creek Formation of eastern Montana and adjacent states has produced one of the richest assemblages of Late Cretaceous vertebrates in the world.  The fauna has been extensively sampled and studied, thanks in large part to the efforts of Jack Horner at MSU's Museum of the Rockies.  The completeness of the Hell Creek fossil record makes it an appealing subject for paleoecological analysis, which is the focus of Horner's new paper.  The authors draw two major conclusions: that the bulk of the large-bodied dinosaurs from Hell Creek represent individuals of intermediate age, while juveniles and old adults are rare, and that Tyrannosaurus was so common that it must have been more ecologically analogous to scavenging, opportunistic hyenas rather than predatory big cats (which require huge amounts of food and are therefore almost always much less common than their prey).  The first point should perhaps not be surprising; as is observed in the paper, there are compelling ecological and taphonomic reasons why very young individuals should not be found at Hell Creek, and it is likewise to be expected that most dinosaurs probably did not survive to extreme old age.  The argument that Tyrannosaurus could not have been an active hunter - the part of the research, incidentally, that has attracted the most media attention - is somewhat more problematic.  Certainly, a modern mammalian predator would not be as abundant as Tyrannosaurus was in the Hell Creek fauna, but using mammals as analogs for dinosaurs has its drawbacks.  Dinosaurs were biologically distinct from mammals (no mammal, for example, could grow to the sizes of sauropods without outstripping their food supply) and the Mesozoic world was fundamentally different from that of today, and as such dinosaurs played by a different set of rules than does anything currently living (including the dinosaurs' descendants, the birds).  Because of this, patterns such as predator/prey ratios that can be very informative when discussing community structure in Cenozoic ecosystems may mean something very different in the Mesozoic, and the preponderance of Tyrannosaurus may be due to biological factors such as metabolism or social structure or to taphonomic biases.  This post may sound like a criticism of Horner et al., but that is not its intent.  In fact, I think the finding that Tyrannosaurus was aberrantly common in the Hell Creek fauna is extremely interesting and certainly the authors' interpretation may be correct.  Further, Hell Creek is one of the only Mesozoic ecosystems that lends itself to fairly robust ecological analysis, and it's excellent that work along those lines is being conducted.  However, at the end of the day, there's a reason dinosaurs are so popular: they are utterly foreign to modern eyes.  This is something of a double-edged sword, because it does make dinosaurs fascinating animals, but it also means they have no good modern analog and that any reconstruction of their ecology will always be cursed with a lower degree of confidence than studies of animals such as reptiles, birds, and, of course, mammals.

Fossil Vertebrate of the Month: Megaloceros giganteus

As my readers are no doubt aware, St. Patrick's Day is this month, and in honor of that March's fossil vertebrate is the extinct animal most strongly associated with Ireland: Megaloceros, the Irish elk.  It's common name, as famously observed by Stephen J. Gould, is a double misnomer, as Megaloceros was not exclusively Irish (it's remains have been found across Eurasia) and while it is a cervid (the largest ever known, in fact), it is not particularly closely related to elk.  However, the earliest specimens to be described were uncovered from Irish bogs, which still yield some of the most impressive Megaloceros fossils.  Because of this, the Irish elk remains something of a national symbol of Ireland, with its remains adorning museums, universities (such as the pair at left from Dublin's Trinity College), and castles alike.  The outsized antlers of Megaloceros males have, unsurprisingly, been the focus of a great deal of research.  Whether they were the product of sexual selection, allometric growth, or some combination of the two has been an area of debate, as has been their role in the animals' extinction.  A long-standing (but somewhat fanciful) hypothesis held that Irish elk went extinct when forests overtook the more open habitats to which they were adapted and that their large bodies and antlers made life in a closed environment impossible.  A more likely culprit is changing climate that ushered in flora that were nutritionally insufficient to support healthy populations of large, antlered animals such as Megaloceros.

Oregon Trail Word Cloud

What's this blog all about?  This word cloud from Wordle pretty succinctly sums up my major themes from the last several months.  Apparently I like ecology a lot, but not as much as the number one.

Humboldt, Bergmann, and Haeckel: The German Roots of Ecology

One of the axioms of science is that any report on your research should include a thorough overview of the topic it addresses. This often means that introductions to scientific papers include some very old citations (for some authors, trying to find the oldest publication you can legitimately cite has become a game, and a pretty fun one at that). I'm in the process of writing the first chapter of my dissertation on the influence - or lack thereof - of climate on body size evolution in mammals, which turns out to be a very long-standing area of study. In working back to the roots of the debate, I've found myself returning to three papers from the early to middle 19th Century, one of which has a direct bearing on my research, another that is a little more tenuously connected, and a third that is only indirectly related but has a profound impact on everything I study. These papers were written by three very different scientists who were studying very different groups of organisms, but all three papers share one major commonality and, as I hope to convince you, several smaller ones as well.

The most recent of these publications is Haeckel (1866): Generelle Morphologie der Organismen by Ernst Heinrich Philipp August Haeckel. Haeckel is remembered today for many things; some of these are positive (he was continental Europe's most eloquent and effective supporter of Darwin and one of the most accomplished scientific illustrators of all time) and some of them very, very negative (he used evolution and his studies on development to justify scientific racism), but he makes an appearance here because it was in his 1866 book that he introduced the word 'ecology' to the world. Haeckel defined his newly-minted word (which roughly translates as 'house study' in Greek) as the study of the environments of organisms. In modern popular culture, environment is often taken to mean the group of abiotic factors - variables such as climate, geography, and geology - that influence an organism, but to ecologists, this is only half the story; organisms also interact with a biotic environment shaped by factors such as predation, competition, and productivity. Ecology, then, is the study of how biotic and abiotic variables influence organisms or, more simply put, the study of why organisms evolve (as opposed to how life has evolved and is evolving, the province of evolutionary biology, though of course there is a huge overlap between the two fields). Because he coined the term, Haeckel is often thought of as the father of ecology, but in fact he would have had no field to provide a name for had it not been for the work of earlier scientists studying the influence of environment on evolution.

One of the most influential of these proto-ecologists was Karl Georg Lucas Christian Bergmann, whose work forms the backbone of my dissertation and of countless other research projects over the course of the last century and a half. Very little biographical information is available for Bergmann: the salient points are that he was born in 1814, attended the University of Göttingen, taught at both his alma mater and at Rostock, and died in 1865, one year before Haeckel wrote his landmark book. While at Göttingen in 1847, Bergmann published the paper for which he is best remembered today: Über die Verhältnisse der Wärmeökomie der Thiere zu ihrer Grösse. The title is a bit of a tongue twister for non-German speakers, but the concept is straightforward enough. Bergmann observed that species of mammals (not individuals within species, as is commonly thought) that lived near the poles tended to be larger than those living towards the equator. Bergmann's explanation for this was that large mammals have small surface area to volume ratios and can therefore retain heat more easily while, conversely, small mammals can shed heat more effectively. Naturally, the poles are colder than temperate regions which are in turn colder than the tropics, and therefore as you head from the former to the latter, you should expect to see a decrease in body size. Bergmann's rule, as this hypothesis has come to be known, has been put to the test several times; his relatively simple explanation has been both supported and attacked by ecologists through the years, but regardless of what you think of his rule, it can't be denied that Bergmann was a pioneering ecologist. By assigning a physical cause to a biotic pattern - and eleven years before Darwin and Wallace introduced the world to natural selection, no less - Bergmann set the tone for generation of ecologists to follow, and as such he deserves to be remembered as a father of the field.

If Bergmann is one of the fathers of ecology, then surely its grandfather was Friedrich Wilhelm Heinrich Alexander Freiherr von Humboldt (1769-1859). As opposed to the relatively obscure Bergmann and the politically distasteful Haeckel, Humboldt is one of the best-known and most beloved figures in the history of science; his Latin American travels and research garnered praise from such luminaries as Edgar Allen Poe, Simon Bolivar, and Thomas Jefferson (himself a scientist of no little reputation) and would inspire Darwin's voyage on the Beagle. While it was his travel narrative that would establish his fame, Humboldt also laid the cornerstone of ecology when, along with his traveling companion Aimee Bonpland, he published Essai sur la géographie des plantes in 1805.  During his sojourn in South America, Humboldt had climbed the volcanic peak of Chimborazo in the Ecuadorian Andes (though he failed to reach the summit) and was struck by the distinct zones of vegetation he encountered during his ascent.  His notes, coupled with observations of similar patterns on European mountains, gave Humboldt the data necessary for his 1805 paper as well as the large-scale figure that accompanied it (itself a milestone of scientific illustration).  By tying vegetation to factors such as temperature, air pressure, and soil type Humboldt became the first scientist to seriously study the influence of the environment on organisms, earning his reputation as a pioneering ecologist as well as countless citations in manuscripts (including mine) over the course of the subsequent two centuries.
The authors of these three papers no doubt had many things in common, but perhaps the most striking is that they shared a country of origin.  At first glance, it seems illogical that ecology should have been born in Germany (which, after all, was only a collection of smaller kingdoms and principalities until 1871).  Germany has always produced great scientists, from Leibniz to Einstein, but in Humboldt's time Paris was the center of the scientific world, and many of the most celebrated accomplishments of 19th Century science took place not on the Continent but across the English Channel.  Even within biology, France and Britain played a dominant role, producing some of the greatest anatomists and, later, evolutionary biologists that have ever lived.  Nonetheless, ecology was, at its root, a uniquely German phenomenon.  This begs a rather obvious question: why?  While I'm a far better paleontologist than historian, I think think I have the glimmer of an answer, but in the interest of keeping unassailable historical facts apart from more baseless arm-waving, I'll save my thoughts for a later post.  Stay tuned...

Fossil Vertebrate of the Month: Megatherium americanum

FVOTM is back from its extended holiday vacation, and because February 12th is Darwin Day, this month's vertebrate is an animal that played a crucial role in the development of evolutionary theory: the giant ground sloth Megatherium americanum.  The species would have been familiar to Darwin before he ever departed on the Beagle: it had been named in 1796 by no less a figure than Baron Georges Cuvier and its size (comparable to that of a modern elephant) and bizarre combination of traits (such as teeth without enamel and claws that the animal evidently walked on) had made it immensely popular.  Darwin himself uncovered fossils of Megatherium - as well as the hippo-like ungulate Toxodon - at Bahia Blanca, south of Buenos Aires.  While it is impossible to pinpoint exactly where or when Darwin first began to understand the patterns that he would later use to support natural selection, his recognition that Megatherium shared many features - including its apparently aberrant teeth and claws - with modern tree sloths certainly represents a milestone, as the great scientist would himself acknowledge in the opening lines of his epochal On the Origin of Species: "When on board H.M.S. Beagle, as naturalist, I was much struck with certain facts in the distribution of the inhabitants of South America, and in the geological relations of the present to the past inhabitants of that continent.  These facts seemed to me to throw some light on the origin of species - that mystery of mysteries as it has been called by one of our greatest philosophers."

Fossil Vertebrate of the Month: Diplodocus carnegii

Last month's Society of Vertebrate Paleontology meeting was held in Pittsburgh and while animal chosen for the conference logo was the awkwardly-named tetrapod Fedexia, there is another animal that will forever be associated with vertebrate paleontology in that city's Carnegie Museum of Natural History. The museum has existed since 1895, but it was in 1898 that its namesake would spur the discovery of its most famous specimen. It's unclear whether Andrew Carnegie was alerted to the publicity value of sauropod skeletons by a visit to the American Museum of Natural History or by a sensational newspaper headline trumpeting the discovery of "The Most Colossal Animal Ever On Earth." Regardless of the cause, he hired away some of the AMNH's paleontologists and sent them to the badlands of Wyoming to find a giant dinosaur for his museum. His team succeeded spectacularly, and in 1901 the fruits of their labor were described as Diplodocus carnegii. The skeleton, which for decades was the longest - though far from largest - dinosaur known, was a huge hit in Pittsburgh and around the world, as Carnegie presented casts of the skeleton (known affectionately as Dippy) as gifts to museums in capitals across the globe. Dippy even has a couple of connections to paleontology in Oregon: D. carnegii was one of the taxa modeled by UO computer scientist/paleontologist Kent Stevens, and the cast presented by Carnegie to London's Natural History Museum was the first fossil I ever saw and was largely responsible for setting me down the path I'm still traveling today.

Research Report: Mexico City

Whenever I tell anyone that I'm a paleontology student, one of the questions I inevitably get is 'Where do you do your field work?' When I tell them that I don't really do field work and that I do my research in the basements of museums, they usually say something to the effect of 'Oh, that's too bad.' Actually, it isn't. For one thing, the best science in our field is done indoors in collections, libraries, and labs. For another, I actually enjoy collections work (you can see a lot more fossils in a day in a museum than you ever will in the field). For yet another, it can take you to some of the best parts of the world. So far my collections visits have brought me home to Seattle, across the Cascades to John Day, to the great cities of California, to the university towns of the Rockies and Great Plains, to New York's unsurpassed temple to natural history, and now they've brought me to one of the greatest, most historic, and culturally rich cities on the planet. I'm writing this post from Coyoacan, a colonial town turned urban neighborhood in Mexico City. I've come to visit the collections of the Universidad Nacional Autónoma de México in order to expand the scope of my dissertation to all of North America rather than just the US. While I've made an avowed effort to cut down on travelogue-type entries on this blog, this is the first international research trip I've taken, and as such a few posts from south of the border might be of more general interest than the usual "this is what I did today and this is what I think of it" travel update. I'll do my best to supply a few of these posts on the state of my research and of paleontology and science in Mexico during the duration of my visit this week, so stay tuned.

Fossil Vertebrate of the Month: Epicyon haydeni

Last month, while measuring teeth in the collections of the University of Montana and Idaho State University, I came across jaws of one of the more impressive carnivores ever to have lived. The picture at left (from UM) may not do the size of the animal justice, but Epicyon haydeni is the most massive known canid; the largest known individuals may have exceeded 200 pounds, putting them well within the size range of modern black bears. Epicyon was a member of a group of canids known as borophagines that were among the most common carnivores of the North American Oligo-Miocene. Borophagines are often described as hyena-like, and many of the larger taxa - including Epicyon - were likely bone-crushing predators. However, the group was very diverse and many of its members, especially in the Oligocene and Early-Mid Miocene, were actually fairly small; at least one species had an almost raccoon-like morphology. In many Late Miocene faunas, two species of Epicyon co-occur: the larger E. haydeni and the smaller (but still very big) E. saevus. Canid experts extraordinaire Xiaoming Wang and Richard Tedford have suggested that this is the result of character displacement, making Epicyon an excellent example of how the fossil record can record ecological and evolutionary patterns.

Fossil Vertebrate of the Month: Oncorchynchus rastrosus

Salmon are a symbol of the Northwest, and with good reason: not only have they been a staple food for humans for millennia and a hugely important link in regional food chains for much longer, but they have very deep roots here. Go back to the Late Miocene and you would still see salmon in the rivers of Oregon; you would, in fact, see one of the most impressive prehistoric fish ever discovered: Oncorhynchus rastrosus, the sabertooth salmon. The features that gave the fish its common name (and its original genus name, Smilodonichthys) are its enlarged canines which, arresting as they are, are not as unusual as they might seem, as many modern salmon grow large breeding teeth while migrating upstream to spawn. The size of O. rastrosus, though, is unique: at lengths of up to 2 meters, it was a good deal larger than the largest known Chinook salmon and head and shoulders beyond sockeyes, its nearest living relatives. The sabertooth salmon was in the news this last month (both in the paper and on TV) after a team led by the University of Oregon's own Edward Davis performed a CAT-scan on its skull. The result of this research is a series of impressive 3-D reconstructions, which can be viewed in an online exhibit by the U of O Museum of Natural & Cultural History; if you'd rather see the original in person, it will be part of the museum's revamped PaleoLab exhibit opening this month.

Field Report: Field Camp 2010

As many of you may know, I was the TA for the paleontology portion of the U of O's field camp this year. Since I got back earlier this week, several people have asked me what we did and what we found. I may not be a great blogger, but even I know the first rule of journalism, so in the interest of giving the people what they want, here's a brief summary of what went on (You'll notice that I'm not giving names or locations of any of the work we did; we were at two sites, both of which are publicly owned, and since illegal collection on federal land is a recurring problem in eastern Oregon, I don't want to provide any information that an unscrupulous fossil poacher might be able to use; for those of you who are wondering, yes, we did have the appropriate permits).

The first site we visited (let's call it Site 1, since imagination is precious and should be conserved) was an exposure of the famous John Day Formation, which has yielded one of the largest and best-preserved Oligocene faunas in the world. Since the primary purpose of our trip was to teach basic paleontological field methods, the bulk of our time was devoted to creating stratigraphic sections for the outcrop. There was, however, time for fossil prospecting as well, and it was very - almost ludicrously - productive. Among the things we uncovered were rodents (particularly squirrels and aplodontids), hypertragulids (mouse deer), canids, nimravids (sabertoothed, cat-like carnivores), horses, entelodonts (bearlike relatives of pigs), and rhinos. Perhaps the most impressive specimens we unearthed were four skulls of oreodonts, pig- and/or sheep-like ungulates that were abundant in the late Oligocene of Oregon (we found ample oreodont postcrania as well, some of which are pictured above).

Our second site (being creative once again, let's call it Site 2) was less fossiliferous but scientifically much more interesting. Instead of just getting a handle on the local stratigraphy as we'd done at Site 1, we were also interested in pinning down the age and paleoenvironment of Site 2, both of which were big question marks going in to field camp. Fortunately, the fossils we found were exactly the ones we'd hoped for to be able to assign an age to the fauna: jaws of the canids Tephrocyon and Cynarctoides, teeth of the horses Archaeohippus and Merychippus, the beaver Monosaulax, and a smattering of camels and paleomerycids (antelope-like ungulates). For those of you who know your North American biostratigraphy, that places you unequivocally in the mid-Miocene (~16 Ma), which in this part of Oregon means you're in the Mascall Formation. Pinning down the paleoenvironment was made easy by the discovery of a bird (probably some kind of waterfowl) and by several shell fragments of pond turtles (I won't insult your intelligence by telling you exactly what the students concluded about the site's paleoecology, but if you can't figure out what environment is likely to be represented by waterfowl and pond turtles, I question whether this is the blog for you).

So there you have it: for a trip whose primary motivation was teaching, we had a remarkably successful couple of weeks in the field (and not just in terms of finding fossils; we were very lucky weather-wise as well, though the last couple of days did manage to break the 100° mark). We and our specimens are now all safely back in Eugene, with the latter awaiting curation and, eventually, a trip back east, where they will be reposited in the collections of John Day Fossil Beds National Monument.

Fossil Vertebrate of the Month: Bradysaurus

In honor of this year's World Cup host, July's fossil vertebrate is South African. Bradysaurus (literally "Slow Lizard," represented here by a skeleton from Berlin's Museum für Naturkunde) was a pareiasaur, a group of large, armored herbivores that may be distantly related to turtles. Though pareiasaurs have been found in late Permian sites throughout the Old World, Bradysaurus is unique to the Karoo Basin north and east of Cape Town. While pareiasaurs were among the largest members of the South African ecosystem, the fauna was dominated by therapsids, or "mammal-like reptiles," including the now-iconic, predatory gorgonopsians and burrowing dicynodonts. The Karoo has been the focus of many research projects in recent years because it is one of the few regions with a terrestrial fossil record of the Permian Extinction, the largest mass extinction in the history of life. Pareiasaurs were among the groups that would not survive the end of the Permian; if you want to see one today, I recommend Oregon's very own Prehistoric Gardens.