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.

The Wide World of Paleontology: Spring 2008

At the end of last quarter, I summed up the high points of our department's paleo discussion group. While the group didn't meet this spring, I thought that it might be fun to sum up the major developments in paleontology during the last few months for the sake of whoever out there still reads this blog. Enjoy!

• The term "missing link" is generally frowned upon, and with good reason, but it can't be denied that discoveries of transitional fossils are always exciting. It may not have the glamor of Lucy or Archaeopteryx, but paleontologists from the University of Calgary described an animal very near the common ancestor of salamanders and frogs this May. Dubbed Gerobatrachus, it lived in the Permian and looked very much like what a salamander/frog would be expected to.
• South America and Australia are both island continents (or at least South America was until Panama appeared on the scene in the Pliocene), and as such have been of interest to paleontologists as long as there has been a science of paleontology. This spring, two papers showed that the continents have more in common than many people may realize. A Cretaceous dinosaur from Victoria and an Eocene mammal from Queensland both show affinities with South American animals; this is no shock, as the two continents were connected until relatively recently, but the results are nonetheless biogeographically interesting. Other extinct Australian organisms to make the news this spring were the giant marsupial Diprotodon, which may be represented by only one species rather than several as had previously been thought, the placoderm fish Gogonasus, a specimen of which was found with an unhatched embryo preserved within it, and the so-called Tasmanian tiger, from which genes were isolated and inserted into a mouse embryo.
• Northwest fossils also found their ways into the headlines in the last few months. Dinosaur bones found in British Columbia several years ago have been revisited by a University of Alberta student, and they may represent a new species. The paleoecology of BC's most famous fossil site has also been revisited, and the result is a food web for the Cambrian Burgess Shale fauna. While not entirely paleontological, coprolites from eastern Oregon have yielded the oldest human DNA from the New World and show - not surprisingly - that the earliest Americans were genetically similar to Siberians.
• The seemingly inexhaustible quarries of Liaoning, China just keep on producing exquisitely-preserved fossil birds and feathered dinosaurs. The early bird Eoconfuciusornis was described by researchers at the University of Bristol, including my former master's supervisor. A former Bristolian made further paleornithological waves by describing a fossil parrot from the Eocene of Denmark, which he nicknamed "Danish Blue" after Monty Python's famous 'Dead Parrot Sketch.'
• My favorite paper this spring was the one that suggested the giant pterosaur Quetzalcoatlus and its relatives did not, in fact, spend much time in the air, but were likely terrestrial predators. This is an interesting hypothesis, as the diet of giant pterosaurs has long been a matter of some debate. It is not unheard of for flying animals to become predominately land-living hunters; the most spectacular example are the flightless, extinct phorusrhacids, but modern storks, secretary birds, and seriemas live similar lifestyles, making the image of Quetzalcoatlus as a predator is at least plausible.

The Wide World of Paleontology: Winter 2008

This quarter saw the return of our department's paleontology discussion group, and over the course of the last few months we've gone over several papers of note. Here are some of the paleontological highlights from the first quarter of 2008:

• Two of my former MSc supervisors, Sarda Sahney and Mike Benton, published a paper on faunal recovery after the Permian-Triassic extinction. Their research yielded two particularly interesting results. First, extinction at the P-T boundary was the last of three extinctions that occurred during the late Permian. Second, ecological recovery took much longer than had previously been thought. Though some organisms - in particular the pig-like reptile Lystrosaurus - survived the extinction and thrived afterwards, ecosystem complexity remained low until 30 million years into the Triassic. You can read Sarda's much more detailed explanation of the paper's findings on her blog.
• My current advisor, Samantha Hopkins, has also published a paper this year. It deals with the issue of rodent body size estimation. In particular, it emphasizes that previous estimates likely overestimate the size of the giant South American rodent Phoberomys, which had been described as "buffalo-sized." Just before this paper came to press, an even larger South American rodent was reported: the cumbersomely-named Josephoartigasia, which was estimated by the authors to weigh 10,000 kg (11 English tons). Unfortunately for fans of giant rodents, this reckoning is likely also too high, though it still would have been a massive animal, far larger than any rodent alive today (as is made abundantly clear in the picture at right at which the skull of Josephoartigasia is compared to a living rat).
• On the paleoclimate front, Wolfram Kürschner and his colleagues published a study of Miocene plant stomata, orifices in leaves that allow carbon dioxide to enter the cells. The density of these openings varies with atmospheric CO2 content, and as such they provide a proxy for climatic conditions. This line of evidence is significant because marine and terrestrial isotopic studies show different climate signals. Stomatal data confirm the pattern observed in the terrestrial isotopic record, showing a period of global warming (the mid-Miocene climatic optimum) between 17 and 15 million years ago, followed by a prolonged period of global cooling.
• Perhaps my favorite paper of the quarter was a description of the Eocene fossil bat Onychonycterus. Before the discovery of this specimen, all fossil bats looked for all intents and purposes like modern forms. This was frustrating, as these fossils told us nothing about the early evolution of bats. Onychonycterus effectively settles one major debate that had been raging in the paleochiropteral community; its ear showed none of the features associated with echolocation in modern species, demonstrating that bats took to the air before evolving "sonar." Even more interesting are the implications for the evolution of bat flight. Onychonycterus has wings similar to those seen in modern bats that fly by intermittent fluttering and gliding. What's more, it had relatively long legs and large claws on its wings, both of which would have made it an adept climber. Taken together, these lines of evidence suggest that the first flying bats were climbing trees and gliding rather than evolving wings from the "ground up" to help them catch insect prey. Another glimpse of early bat evolution was provided by fossil from the Fayum of Egypt, where - among others - a giant species was recently described.
• There were several other stories in paleontology that we didn't discuss in our group that deserve mention anyway. Fellow Bristol and Chicago alumnus Steve Brusatte has described two new carnivorous dinosaurs from Africa. Dinosaurs weren't the only big things around in the Mesozoic, though, a point underscored by the discovery of a giant, dinosaur-eating frog (shown at right). Our Primate ancestors seem to have been part of the dinosaurs' world for longer than expected as well, and our own species seems to have evolved into more diverse niches than we had previously realized. One thing our species is not, according to a U of O anthropologist, is a duck-killer. The debate over how old ducks and their relatives really are rages on, but at least one contentious issue seems to have been solved: if a modern lion and an extinct marsupial "lion" got in a fight, who would win?