October 23, 2012
The annual Society of Vertebrate Paleontology meeting is a test of endurance. The science comes fast and furious in presentations, posters, hallway conversations and shouted exchanges over the din of the bar, with no consideration for how dehydrated, weary or hungover you might be. (Paleontologists study hard and party harder.) By the last day, my brain ached with details of flying Microraptor, bounding crocodiles, marsupial bone microstructure and dozens of other topics. When my friends at the conference asked “What did you like best?” after the technical sessions finally concluded, I was only capable of grunts and indelicate gestures.
I’ve had a day to settle down and process what I saw. And I know this–at SVP, dinosaurs rule. This isn’t to say that the conference is all about the Mesozoic celebrities. I saw many excellent talks on prehistoric fish, mammals, amphibians and other forms of ancient life. But, for a dinosaur fan, SVP offers a glut of dinosaur science from new discoveries about the beloved Tyrannosaurus rex to brand-new species that have only just come out of the ground. Since this blog is called Dinosaur Tracking, I’m going to focus on some of the stand-out dinosaur science I saw during the meeting.
Montana State University graduate student Jade Simon’s presentation focused on giant Cretaceous dinosaur eggs found in Idaho, but the implications of the discovery were what really grabbed by attention. According to Simon and her collaborators, the pair of elongated, oblong eggs most closely match those found in the nests of oviraptorosaurs–beaked, feathered theropods like Citipati and eponymous Oviraptor. Yet the two eggs were so large that they suggested a dinosaur of prodigious size, on the scale of the 25-foot-long Gigantoraptor recently found in China. If Simon and coauthors are correct, then an enormous, as-yet-undiscovered oviraptorosaur strutted around Idaho around 100 million years ago. The next step–finding this fantastic creature’s bones.
Simon wasn’t the only researcher showing off dinosaur eggs. Just prior to her presentation, meeting attendees were treated to a pair of talks about dinosaur embryos found in the Late Jurassic rock of Portugal. These deposits are similar in age to those of the famous Morrison Formation of the American west and share many of the same types of dinosaurs. An embryo studied by Ricardo Araújo and coauthors appears to be a nascent Torvosaurus–a giant Jurassic carnivore that topped Allosaurus in bulk–and paleontologist Octávio Mateus followed with a skeletal embryo of Lourinhanosaurus, a mid-size theropod dinosaur found in the same formation. The embryo described by Mateus stood out because it was found by his parents–amateur paleontologists–in a nest of 100 eggs, including crocodile eggs mixed in with those of dinosaurs. Was this nest a communal site used by many mothers? The embryo and the nest it was found in will definitely help us better understand how some baby dinosaurs entered the world.
The SVP crowd also got treated to previews of various dinosaurs that are slowly making their way to press. Researcher Corwin Sullivan presented some scrappy evidence that a second giant tyrannosaur might have lived alongside the recently named Zhuchengtyrannus, and Nathan Smith showed off some new material from what may be two new species of sauropodomorph dinosaurs collected from Antarctica. Oliver Rauhut added to the list with a new theropod from Argentina that looks like a more archaic version of Allosaurus, and visitors to the poster session got to check out what might be a new species of Diabloceratops that Eric Lund and his colleagues have been working on. Most of the new dinosaur presentations followed the same format–where the fossils were found, how much of the skeleton was found, what sort of dinosaur the species is–but, in time, we should get fuller details of these dinosaurs in progress.
But not all the presentations at the conference were on new field discoveries. Increasingly, paleontologists are scanning, slicing and otherwise studying fossils in new ways, drawing ever more data about dinosaur biology from old bones. The first talk I walked into, by Eric Snively, reconstructed the neck musculature of Allosaurus for insights into the feeding behavior of this Jurassic hypercarnivore. As it turned out, Allosaurus probably had quite a strong neck and used this power to stabilized its flexed head while ripping flesh from prey–think of a giant, toothy falcon. In another session, Jason Bourke created virtual models to examine whether sauropod dinosaurs such as Camarasaurus and Diplodocus had their nasal openings on the tops of their heads–as was shown when I was a kid–or had nostrils further down the snout. The airflow models better fit the nose-at-end-of-snout model, although, as Bourke pointed out, there’s still quite a bit we don’t know about sauropod soft tissues.
Unsurprisingly, Tyrannosaurus got some love, too. Sara Burch reexamined the shoulders and forelimbs of old T. rex in an attempt to reconstruct the dinosaur’s musculature. Among other things, Burch found that the dinosaur’s arms underwent significant functional changes over time. The arms of the tyrant weren’t fading away, but modified for different uses than that of earlier relatives. What exactly the dinosaur was doing with its infamously small arms, though, we still don’t know.
Within the various new areas of research, though, dinosaur histology has been providing paleontologists with some of the most tantalizing details of prehistoric biology. My friend Carolyn Levitt presented her new research on the microstructure of Kosmoceratops and Utahceratops bones. These horned dinosaurs didn’t show any lines of arrested growth (LAGs) in their bones–rings thought to mark annual slowdowns in bone growth and often used to roughly age dinosaurs–while previously studied dinosaurs from more northern sites in North America do show these markers. This might mean that, like mammals, dinosaurs maintained high-running metabolisms but their growth was still influenced by environmental pressures, such as cold or dry seasons, in their surrounding environment. In a time of scarce resources, dinosaurs in highly seasonal habitats probably slowed their growth while those in lusher environments did not face the same pressures. Indeed, the dinosaurs with the most LAGs were the northernmost, while Utahceratops and Kosmoceratops were the southernmost sampled.
In a similar vein, a poster by Julie Reizner looked at the histology of the horned dinosaur Einiosaurus and what the microstructure details might say about the ceratopsid’s biology. The sampled dinosaurs, found in a rich bonebed, suggest that growth in Einiosaurus slowed at about three to five years of age, which might mean that these dinosaurs made a dash for reproductive maturity before their growth slowed. The fact that Reizner’s animals were predominately young and perished long before full skeletal maturity–or, in other words, still had some growing to do–is consistent with the idea that dinosaurs generally lived fast and died young.
And I would be remiss if I didn’t mention that there was an entire session devoted to Appalachia–a Late Cretaceous subcontinent formed when a shallow sea split North America in two, of which my former New Jersey home was a part. Paleontologists have made fascinating discoveries on the sister continent, Laramidia, but Appalachia has often been ignored given that we as yet knew little of the dinosaurs that lived there. Still, there is much to be learned by going back to the fragmentary and rare dinosaurs of that early eastern landmass. In addition to featuring Dryptosaurus, New Jersey’s fearsome tyrannosauroid, Stephen Brusatte reexamined the few remains of “Ornithomimus” antiquus. This ostrich-like dinosaur probably belonged to a different genus and was not as primitive as previously thought. Shortly after Brusatte’s talk, Matthew Vavrek spoke about dinosaurs found in the high Arctic of Appalachia. Hadrosaurs, deinonychosaurs, tyrannosaurs and others lived along the northwestern coast of the continent and may help use better understand the differences between Appalachia and Laramidia. The most frustrating aspect of all of this is that the eastern dinosaurs are so poorly known–we need more dinosaurs.
The findings I mention here are just a scattered sampling of SVP, based upon the talks and posters I personally encountered. With three sessions going at the same time, it was utterly impossible to see everything. (Please chime in about your own favorite presentations in the comments.) Nevertheless, it was amazing to see paleontologists showing off new finds and going back to fossil collections for new information. We’re learning more, at a faster rate, than ever before. As multiple experts said to me during this conference, it’s a great time to be a paleontologist. The SVP dinosaur sessions left no doubt of that, and I can hardly wait for next year.
Thankfully, many other paleontologists have been sharing their thoughts about the conference through the #2012SVP Twitter hashtag and on their blogs. For an outsider’s perspective on the conference, see Bora Zivkovic’s rundown of the meeting, as well as Victoria Arbour’s summary of SVP silliness. Out of everything, though, I think this year’s attendees will all remember the conference center’s whoopee cushion chairs–caught on video by Casey Holliday’s lab. I hope that next year’s conference in Los Angeles is just as exhausting, and just as fun.
November 21, 2011
Earlier this month, paleontologists from around the world convened in Las Vegas for the 71st annual Society of Vertebrate Paleontology conference. Preliminary findings were shared, new discoveries were presented, and researchers caught up with friends and colleagues, but not all the news came from the meeting halls. Various field trips held just before the conference introduced paleontologists to the geology and paleontology in the vicinity of Las Vegas, Arizona, and southern Utah. One of them confirmed the traces of a dinosaur not far from the bright lights of the Las Vegas strip.
An article in the Las Vegas Review Journal has the details. About twenty minutes outside of Las Vegas, within the Red Rock Canyon National Conservation Area, lie the tracks of a relatively small theropod dinosaur in the red, roughly 190-million-year-old Early Jurassic rock. Our knowledge of dinosaurs in North America from this time is relatively sparse. Very few skeletons have been found from this period, and much of what we know about the dinosaurs of the Early Jurassic Southwest comes from tracksites. For the moment, these three claw-tipped toe impressions indicate that the Red Rock Canyon dinosaur was a small theropod. Details of the dinosaur’s behavior, such as how fast it might have been walking, have not yet been studied.
The interpretation of the Red Rock Canton site will emerge as research is conducted. According to the LVRJ story, Bureau of Land Management officials are planning to create casts of the tracks to let visitors learn about the site without risking damage to the ancient footprints. If you’re in the area and are really itching to see some dinosaur tracks, though, there are other opportunities within a few hours drive: the Dinosaur Discovery Site in St. George, Utah is packed with similar Early Jurassic dinosaur footprints.
November 7, 2011
After a week packed with presentations, posters and lots of paleo-goodness, the 71st annual Society of Vertebrate Paleontology meeting is over. There’s not much to be sad about, though. If the conference is any indication, we’re going to be seeing lots of fascinating dinosaur stories in the coming weeks, months and years.
There were far too many dinosaur presentations to attend them all, but the big-picture trend is that paleontologists are able to pull ever-more information about dinosaurs out of their bones and geological context. Last week I wrote about the meeting’s Laramidia session, in which paleontologists pondered the distribution and evolution of horned dinosaurs, hadrosaurs, tyrannosaurs and other Late Cretaceous celebrities up and down the western subcontinent. These discussions consequently fed into the ongoing debate about how diverse dinosaurs were and whether we have named too many species. In a poster presented on the last day of the conference, Museum of the Rockies paleontologist Denver Fowler proposed that some horned dinosaurs such as Mojoceratops, Titanoceratops and Kosmoceratops are really different stages of previously named dinosaurs such as Chasmosaurus and Pentaceratops. There was quite a bit of discussion and arguments about this proposal—just as with the idea that Torosaurus is really a grown-up Triceratops—but that’s not a bad thing. By combining anatomy, histology, biogeography and other lines of argument, paleontologists may be able to get some better resolution about how dinosaurs actually lived and the big patterns of their evolution. Yes, there are going to be controversies and debates, but that is a positive thing that speaks to the current vibrancy in the field of study.
Attendees also got an early look at previously unknown and little-studied dinosaurs. On Saturday morning Max Langer from the Universidade de São Paulo presented a report on an early sauropodomorph dinosaur found in the Late Triassic Santa Maria Formation of Brazil. The skull was vaguely reminiscent of Eoraptor—a dinosaur hypothesized to be a sauropodomorph and not a theropod in a paper published early this year—and this new dinosaur was apparently close to the origins of the varied and successful group of dinosaurs which would eventually contain giants such as Apatosaurus and Giraffatitan. But not all the undescribed dinosaurs mentioned at the session were new. At the SVP reception held at the Carnegie Museum of Natural History last year, I saw the reconstructed skeleton of a strange oviraptorid dinosaur from North America. This toothless, crested creature is known from several partial skeletons but has been little studied until now. That’s why I was glad to see a presentation by Carnegie Museum of Natural History paleontogist Matt Lamanna, which presented the animal as the best-known oviraptorid dinosaur from our continent. Even though ovirpatorids remains have been found in North America before, they were so scrappy that their counterparts in Asia filled in most of what we know about these dinosaurs. The yet-unnamed oviraptorid Lammana described will help fix this problem, and will provide another way for paleontologists to investigate the trade of different dinosaur lineages between North America and Asia during the Late Cretaceous.
New technologies and sophisticated methods are also being used to fill out our understanding of dinosaur biology. Paleontologists are agreed that dinosaurs were active, dynamic and fast-growing animals, but how they achieved this lifestyle is still a matter of investigation. In a talk in the theropod dinosaur session, paleontologist Mark Goodwin from the University of California Museum of Paleontology in Berkeley presented results that tested the conclusions of an earlier study about the physiology of Tyrannosaurus rex. The earlier study had used oxygen isotopes—chemical signals locked in bones and teeth that can be compared to determine things like temperature—to determine that Tyrannosaurus was probably a homeothermic endotherm, that is, it generated heat internally and maintained a constant body temperature. But when Goodwin took a greater sample of chemical isotopes from Tyrannosaurus bones, he found that the body temperature of the animal probably fluctuated. This would mean that Tyrannosaurus, like some birds, was an endothermic heterotherm—the dinosaur generated heat internally but had a body temperature that varied on a regular basis. Thinking of dinosaurs as “hot-blooded” or “cold-blooded” doesn’t do justice to the variety of physiological characteristics biologists know about.
The terminal end of dinosaur lives also got some attention in a presentation by Alicia Cutler of Brigham Young University on why the classic head-back, tail-up death pose is so common in dinosaurs. Cutler used fresh and frozen chickens to see how immersion in water affected the posture of the dead birds. Although not all her videos of the experiments worked, those that did showed that the necks of the chickens arched back almost immediately upon becoming immersed in water. The pose was not the result of drawn-out periods of dessication as some paleontologists had thought. In addition to previously proposed hypotheses, such as the idea that the pose could be created during the death throes of the animals, the experiments may help fill in our understanding of how particular dinosaurs died and became preserved.
Obviously, I have left out many studies. I can’t possibly do justice to the entire meeting, and I undoubtedly missed some intriguing presentations and posters. (Although, on the other hand, if I absorbed everything my brain probably would have exploded from paleo-overload.) There were many previews of soon-to-be-published work and ongoing research, and the smattering I was able to see underscored the point that our understanding of dinosaurs is constantly in flux and growing ever deeper. I can hardly wait for next year’s meeting in North Carolina, where I may even be able to present something about a research project I am just now embarking on. Stay tuned.
November 3, 2011
“The fossil record is incredible when it preserves things,” paleontologist Jack Horner said during his talk about dinosaurs and evolution the other night, “but it’s not a complete record.” Many of the sessions and posters I have seen at the annual Society of Vertebrate Paleontology meeting so far are a testament to that truth, either in a positive or negative sense.
In one of the most talked-about presentations delivered so far, McMaster University masters student Ben Novak brought up some substantial obstacles that he and his co-authors have discovered to the hypothesis that remnants of dinosaur soft tissues and proteins have been found in the fossil record. The evidence for long-lived Tyrannosaurus goo may not be as good as previously thought, Novak explained, and the record of proposed dinosaur soft tissue remnants accumulated so far should be reexamined. The fossil record may not be as kind to us with dinosaur remnants as we would like.
Then again, there were notices of some exquisite finds which will provide researchers with a way to better understand dinosaur lives. A poster created by paleontologists Jingmai O’Connor, Zhou Zhonghe and Xu Xing from Beijing’s Institute of Vertebrate Paleontology and Paleoanthropology presented fossil evidence for a Cretaceous turducken. Inside the gut contents of the non-avian, feathered dinosaur Microraptor were the partial remains of a prehistoric bird, and the fact that the bird probably lived in the trees may provide some supporting evidence for the notion that Microraptor may have also been an arboreal animal. Like anything presented at the conference, these findings will be further researched, scrutinized and hopefully published, but such preliminary announcements illustrate the difficulties and the wonders of the fossil record.
But not all the cool announcements are exclusive to SVP. Significant new discoveries pop up regularly in journals, and one that caught my eye is the first description of a Protoceratops nest by University of Rhode Island paleontologist David Fastovsky and colleagues in the Journal of Paleontology. This discovery has been a long time coming.
During the 1920s, American Museum of Natural History expeditions to Mongolia brought back, among other things, dinosaur eggs that they attributed to the horned dinosaur Protoceratops. The researchers were so confident in this assignment that the remains of a small theropod dinosaur found in the same deposits as the supposed Protoceratops eggs was named Oviraptor: “egg thief.” Restorations of Protoceratops parents guarding their nests from Oviraptor hungry from an omelet proliferated through dinosaur books. But reexamination of those eggs during the 1990s showed that paleontologists had the story wrong. Developing dinosaurs preserved inside some eggs were actually oviraptorid dinosaurs—the “egg thief” was more likely a parent! Good thing for us Oviraptor can’t sure for defamation of character.
How Protoceratops nested once again became a mystery, as paleontologists continued to amass more evidence of oviraptorid nests. The closest thing to a Protoceratops nest was an aggregation of small, juvenile dinosaurs found in China and attributable to an evolutionary cousin known as Psittacosaurus. But the new paper by Fastovsky and colleagues documents a rare discovery than can give us some insight into how Protoceratops reproduced and grew up.
The nest in question was found in the roughly 84- to 75-million-year-old strata of the Upper Cretaceous Djadokhta Formation in central Asia. Rather than being a nest full of eggs, though, this Protoceratops nest is packed with baby dinosaurs. Fastovsky and co-authors count as many as 15 juvenile animals inside the nest, but these were not newborns. The degree of skeletal development among the little dinosaurs and a lack of eggshells within the nest indicates that they had already been in the nest for some time. Sadly, these little dinosaurs were buried alive, probably by a sandstorm.
What this discovery indicates about parental care in Protoceratops is uncertain. No adult dinosaur was found in association with the babies. Perhaps the adult continued to care for the little dinosaurs while they remained in the nest, or perhaps they left the nest and the baby dinosaurs remained together in the nest area. With any luck, future discoveries will provide more insight into these points. Nevertheless, the new find adds to the growing body of evidence that many dinosaurs stuck together as juveniles. Their tragedy is a boon for paleontologists hoping to understand dinosaur lives.
Fastovsky, D., Weishampel, D., Watabe, M., Barsbold, R., Tsogtbaatar, K., & Narmandakh, P. (2011). A Nest of Protoceratops andrewsi (Dinosauria, Ornithischia) Journal of Paleontology, 85 (6), 1035-1041 DOI: 10.1666/11-008.1
November 2, 2011
What can dinosaurs teach us about evolution? Charles Darwin mostly ignored them during his career, and evolutionary patterns are often easier to study in creatures that left more numerous fossils, such as trilobites and the tiny, armored plankton called foraminiferans. Yet, as paleontologist Jack Horner explained during a lecture at the 71st annual meeting of the Society of Vertebrate Paleontology last night, what we have come to know about dinosaurs can illustrate big-picture evolutionary facts.
Despite the fact that Horner was addressing an audience of scientifically minded peers, his talk was very simple. I wouldn’t be surprised if it became a regular lecture on Horner’s speaking circuit to schools and public venues. There were no technical graphs of data points or tables of measured variables. Instead, Horner began with the nuts and bolts of how to find a dinosaur in the Montana badlands. Many people have the impression that paleontologists just walk out into the badlands and dig holes, but as Horner pointed out, simply digging random holes won’t help you find anything. Dinosaurs are gifts of erosion—we find dinosaurs when they are already coming out of the ground. From there, Horner explained, he typically tasks a cadre of graduate students with the back-breaking parts of the excavation and soon whatever there is of the dinosaur skeleton becomes exposed.
Once those bones are out of the ground and cleaned up, all the fun technical nitpicking can start. Horner used dinosaur color as an example. Although I was disappointed that he didn’t mention our recently gained ability to detect the colors of some dinosaurs from fossil feathers, Horner pointed out that we don’t really know anything for sure about the color patterns of most dinosaurs. Horner also mentioned his own work on some evolutionary patterns among Cretaceous dinosaurs in the Two Medicine Formation, specifically whether the horned dinosaur Rubeosaurus was gradually modified into Pachyrhinosaurus in a straight line of descent through several other transitional types within the geologic formation or whether the different dinosaurs in question represent a branching evolutionary pattern. “We paleontologists love to argue about this,” he said, and pointed out that the assembled group had come to the conference to argue, after all. But, Horner quickly added, we don’t argue about the fact of evolution. We can go back and forth indefinitely about the minutiae of paleobiology and the patterns of evolutionary change, but vertebrate paleontologists agree that evolution is a fact.
So what do dinosaurs have to do with the fact of evolution? Horner outlined five different proofs of evolution: three proofs that Darwin cited, a “test” proof, and what Horner called the ultimate proof. The first on the list was simply descent with modification. Horner cited the many strange breeds of dogs and chickens as an analog for how organisms can become drastically modified over the course of history. Humans specifically selected for those changes in the domesticated animals, but as Darwin illustrated in On the Origin of Species and other works, the changes that dogs, chickens and other animals have undergone underscores the fact that the same thing is happening due to entirely natural causes every second and every day. To greater or lesser extents, lineages of organisms change over time, and the fossil record demonstrates this beautifully.
Next on the list were rudimentary features: structures that once served a particular function but became vestigial organs that don’t carry out that same function anymore. (Keep in mind, though, that “vestigial” does not mean “useless.”) Horner cited the modified wings of flightless birds and the remnants of hind limbs in whales as modern day examples, and identified the small forelimbs of Tyrannosaurus as another. Since the time the tyrant dinosaur was discovered, paleontologists have been asking, “What did it use those arms for?” Horner concluded that Tyrannosaurus probably didn’t do more than scratch its belly after a big meal with them. That point is debatable, but we do know that tyrannosaur forelimbs did become greatly reduced in size during the evolutionary history of their lineage. Horner’s hypothetical “chickenosaurus” even made a cameo here. Tweaks in the genetics and development of chickens can cause the reappearance of long-lost traits, such as teeth, and by carrying out these experiments Horner hopes to understand which genes and developmental quirks were key in the evolution of birds from non-avian dinosaurs.
In a phrasing that sounded appropriately Victorian, Horner then moved on to evolutionary proof from the “geological succession of organic beings.” Simply put, we find fossils in layers, in successions of strata that together span hundreds of millions of years. Fossils are not all together in one big clump (as would be expected if the entire fossil record were attributable to the biblical flood as many young earth creationists claim). You’re not going to find a prehistoric horse in the 150-million-year-old Jurassic limestone quarries of Germany, and you’re certainly not going to find a dinosaur in the 505-million-year-old rock of the Burgess Shale. But Horner said that he encourages creationists who want to believe in alternate histories to go looking for the out-of-place fossils they think they’re going to find. “I encourage people who don’t believe in evolution to look for horses in Jurassic Solenhofen limestone,” Horner said, especially since those searches may be much more useful in turning up new specimens of the feathered dinosaur and archaic bird Archaeopteryx.
Horner covered his last two points very quickly. The “test proof” for evolution, he proposed, comes through testing genetic relationships. We don’t yet have genetic material from Mesozoic dinosaurs, and we may never have it, so paleontologists will have to continue to rely on anatomy as they strive to sort out the dinosaur family tree. But the ultimate proof has nothing to do with the animals themselves. The ultimate proof of evolution, Horner quipped, is “ego.” Scientists are constantly arguing with each out about the patterns and processes of evolution, and scientists love to disprove ideas. Anyone who managed to show, beyond a shadow of a doubt, that evolution doesn’t happen would be the most famous scientist of all time, yet no one has been able to do this. Despite the best efforts of scientists to disprove ideas and their penchant for arguing over the nature of nature, the evidence for the fact of evolution keeps getting stronger and stronger.