November 9, 2012
It’s a good time to be a ceratopsid fan. Since 2010, paleontologists have introduced us to a slew of previously unknown horned dinosaurs, and new discoveries are continuing to trickle out of field sites and museums. Long-forgotten specimens and unopened plaster jackets, especially, have yielded evidence of ceratopsids that researchers overlooked for decades, and this week Royal Ontario Museum paleontologist David Evans and colleagues have debuted yet another horned dinosaur that was hiding in storage.
The Late Cretaceous exposures of Alberta, Canada’s Belly River Group are rich with ceratopsid fossils. For over a century, paleontologists have been pulling bones of the fantastically ornamented dinosaurs from these badlands. Yet most of the ceratopsids from this area have been found in the Dinosaur Park Formation, and researchers have paid less attention to the older strata of the Oldman and Foremost Formations nearby.
The Foremost Formation, in particular, has received little attention because diagnostic dinosaur remains seem to be rare within its depths, but a few notable specimens have been found in this slice of time. In 1958, paleontologist Wann Langston, Jr. and a crew from what is now the Canadian Museum of Nature pulled fragments of several ceratopsid specimens from 78-million-year-old deposits in the Foremost Formation. Those bones and skeletal scraps sat in collections for years until they caught the eye of Evans and Michael Ryan (the lead author of the new study) as they made the research rounds for their Southern Alberta Dinosaur Project. Although fragmentary, Langston’s fossils were from a new genus of ceratopsid.
Evans, Ryan and Kieran Shepherd have named the dinosaur Xenoceratops foremostensis in their Canadian Journal of Earth Sciences study. The dinosaur’s name–roughly “alien horned face”–isn’t a testament to the ceratopsid’s distinctive array of horns but to the rarity of horned dinosaur fossils within the Foremost Formation. Indeed, despite Danielle Dufault’s gorgeous restoration of the dinosaur, Xenoceratops is presently represented by skull fragments from several individuals. The researchers behind the new paper pieced them together to create a composite image of what this dinosaur must have looked like, and, in turn, discern its relationships.
Based upon the anatomy of one of the dinosaur’s frill bones–the squamosal–Evans and coauthors are confident that Xenoceratops was a centrosaurine dinosaur. This is the ceratopsid subgroup containing other highly decorated genera such as Styracosaurus, Spinops, Centrosaurus and another dinosaur given a new name in the same paper, Coronosaurus (formerly “Centrosaurus” brinkmani). The other ceratopsid subgroup, the chasmosaurines, encompass Triceratops, Torosaurus and other genera more closely related to them than Centrosaurus.
At approximately 78 million years old, Xenoceratops is currently the oldest ceratopsid known from Canada, beating out its cousin Albertaceratops by half a million years. Given the age of Xenoceratops, and the fact that it had long brow horns and a short nasal horn, instead of the long nasal horn-short brow horns combo seen in its later relatives, it isn’t surprising that the dinosaur seems to be at the base of the centrosaurine family tree. This means that Xenoceratops can help paleontologists examine what the early members of this significant ceratopsid group were like and how drastically centrosaurine ornamentation changed. “Xenoceratops has very well developed frill ornamentation comprised of a series of large spikes and hooks, occurring at multiple parietal loci, that foreshadows the great diversity of these structures in other species that occur later in the Campanian,” Evans says, and this indicates that “complex frill ornamentation is older than we may have thought.”
Still, Evans cautions that Xenoceratops is presently a very scrappy dinosaur. We need more fossils to fully reconstruct this dinosaur and confirm its place in the ceratopsid family tree. The dinosaur’s “true significance in terms of ceratopsid origins will only be revealed with further discoveries,” Evans says, particularly between the time of the slightly older Diabloceratops found in southern Utah, and the even more archaic, roughly 90-million-year-old ceratopsian Zuniceratops. “Our record of ceratopsians in this critical part of their family tree is still frustratingly poor,” Evans laments. In fact, paleontologists know relatively little about dinosaur diversity and evolution during the middle part of the Cretaceous–a critical evolutionary time period for ceratopsians, tyrannosaurs and other lineages that came to dominate the Late Cretaceous landscape. If we are ever going to solve the mystery of how ceratopsids evolved, and why they were such garishly adorned dinosaurs, we must search the lost world of the mid-Cretaceous.
Ryan, M., Evans, D., Shepherd, K. 2012. A new ceratopsid from the Foremost Formation (middle Campanian) of Alberta. Canadian Journal of Earth Sciences 49: 1251-1262
August 3, 2012
Dinosaurs didn’t all live at the same time. Not counting the avian species that have thrived during the last 65 million years, dinosaurs proliferated throughout the world during a span of over 160 million years. As I’ve pointed out before, it’s amazing to think that less time separates us from Tyrannosaurus than separated Tyrannosaurus from Stegosaurus.
Even within specific geologic formations, not all the dinosaurs found in those layers lived side by side. Dinosaur-bearing strata accumulated over millions and millions of years and record both ecological and evolutionary changes. Look closely enough, and you can even see particular communities of dinosaurs give way to different assemblages. In an in-press Palaeogeography, Palaeoclimatology, Palaeoecology paper, Jordan Mallon and colleagues have done just that.
Canada’s Dinosaur Park Formation is one of the most spectacular slices of Late Cretaceous time found anywhere in the world. Spanning approximately 76.5 to 74.8 million years ago, the formation has yielded lovely specimens of dinosaurs such as the crested hadrosaur Corythosaurus, the spiky ceratopsid Styracosaurus, the lithe tyrannosaur Gorgosaurus, the heavy-armored ankylosaur Euplocephalus and many others. Not all of these dinosaurs were neighbors, though. Since 1950, at least, paleontologists have recognized that some kinds of dinosaurs are restricted to certain slices of the formation, and the dinosaur community changed over time. Mallon and co-authors decided to have another look at the dinosaur turnover, focusing on the large herbivores and investigating what might have shook up the dinosaur populations during the time the Dinosaur Park Formation was being laid down.
The paleontologists identified two broad divisions in the Dinosaur Park Formation, which they call “megaherbivore assemblage zones.” Each zone lasted roughly 600,000 years each. There are a lot of names here, so bear with me. In the lower zone, the horned dinosaur Centrosaurus and the crested hadrosaur Corythosaurus are found throughout; other dinosaurs restricted to this half of the formation include the ceratopsid Chasmosaurus russelli, the hadrosaurs Gryposaurus and Parasaurolophus, and the ankylosaur Dyoplosaurus.
Yet there are some dinosaurs that first appear in the lower zone and persist into next one. The ceratopsid Chasmosaurus belli, the ankylosaur Euoplocephalus and the hadrosaurs Lambeosaurus clavinitialis and Lambeosaurus lambei show up in the lower zone but pass through into the second zone as well. And, as with the lower swath, there were dinosaurs that were only found in the second zone. The hadrosaurs Prosaurolophus and Lambeosaurus magnicristatus, as well as the horned dinosaurs Styracosaurus, Vagaceratops and a pachyrhinosaur, are only found in the upper zone.
So the big picture is that the lower zone is characterized by Centrosaurus and Corythosaurus, the upper zone is distinguished by Styracosaurus and Prosaurolophus, and there are some dinosaurs–such as Lambeosaurus and Chasmosaurus–that are smeared across the two. As the researchers note, it’s even possible to break down the two halves into even smaller subsets, although the picture gets a little muddier at these levels.
What does all this evolutionary dinosaur shuffling mean? Other researchers have proposed that the Dinosaur Park Formation represents a series of turnover pulses–after a period of stability, rapid ecological change wiped out some dinosaurs while creating opportunities for a new community. The now-vanished Western Interior Seaway has been invoked as a possible mechanism for this. As this shallow sea, which once split North America in two, expanded and encroached further inland, the area of the Dinosaur Park Formation became a mostly coastal, muddy, swampy habitat. This may have put pressure on some forms of dinosaur while providing opportunities for others. As the seaway fluctuated, the attendant changes would have altered the environment and therefore affected dinosaur populations.
According to Mallon and collaborators, though, there’s no strong evidence for the turnover pulse hypothesis. We simply don’t have the resolution to tell how closely certain dinosaurs were tied to particular habitats or niches, and shifts in ecology would have influenced dinosaur evolution. Other possible influences–such as dinosaurs migrating to the area from elsewhere, or the evolution of one species into another within the formation–are also frustratingly unclear. As the researchers state, “Whether the appearance and disappearance of the megaherbivorous taxa of the [Dinosaur Park Formation] was due to evolution, migration, or to a combination of these factors, is difficult to determine.” We don’t yet know what drove the alterations in the formation’s dinosaur communities.
Aside from the ongoing mystery about what caused the changes between the two zones, the revised look at the Dinosaur Park Formation also raises a few questions about dinosaur ecology. Despite the shifts in dinosaur communities, the paleontologists note, there were about six to eight different megaherbivorous dinosaur species living alongside each other. That’s a lot of big herbivores on the landscape, especially since the hadrosaurs and ceratopsids may have formed huge herds. Such vast, hefty dinosaur communities would have required a large amount of vegetation, and the disparate megaherbivores were in competition with each other for food. In order to live alongside one another, then, we can assume that there was some kind of niche partitioning–the dinosaurs were adapted to have restricted diets or live in particular habitats as a result of their competition for resources. How exactly this happened, though, requires further study into the ecology and evolution of these dinosaurs.
And there was something else that caught my eye. The new study focused on the megaherbivores, but what about the large carnivores? The large tyrannosaur Gorgosaurus was also present in the Dinosaur Park Formation and was rejected by the researchers as a zone marker because this theropod ranges throughout the formation. Think about that for a moment. We can see a significant amount of change and turnover among the big herbivores, but one of the large carnivores stays the same throughout the entirety of the formation. Why should this be so? Perhaps it has something to do with the fact that the ornamentation and headgear of hadrosaurs and ceratopsids changed quite a bit, but their general body plans were conservative–a Gorgosaurus could take down a Corythosaurus just as well as a Lambeosaurus.
Likewise, I wonder if the same pattern might hold true elsewhere. The Kaiparowits formation of southern Utah, laid down around the time of the Dinosaur Park Formation further north, also hosts an array of hadrosaurs, ceratopsids and ankylosaurs, but there seems to be just one large dinosaurian predator, the tyrannosaur Teratophoneus. (The giant alligator cousin Deinosuchus was another megacarnivore in the Kaiparowits.) We need more fossils to be sure, but perhaps, like Gorgosaurus, the short-snouted Teratophoneus remained the same as different large herbivores came and went. If this turns out to be the case, the lack of an arms race between predator and prey would be further evidence that the ornamentation of ceratopsids and other dinosaurs had more to do with decoration and combat among each other than defense.
Indeed, the new study of the Dinosaur Park Formation lays some important groundwork for future studies. Paleontologists are currently investigating and debating why the roughly 75-million-year-old dinosaurs from Alberta are different from the roughly 75-million-year-old dinosaurs from southern Utah. What factors drove the diversity and disparity of these dinosaurs across the latitudes, and who really lived alongside whom? So far, the Dinosaur Park Formation is the best-sampled slice we have, and there is much work to be done. With any luck, and a few more decades of careful sampling, we’ll be able to put together an intricate picture of how dinosaurs lived and evolved during this brief span of Late Cretaceous time.
Mallon, Jordan C., Evans, David C., Ryan, Michael J., Anderson,, & Jason S. (2012). Megaherbivorous dinosaur turnover in the Dinosaur Park Formation
(upper Campanian) of Alberta, Canada Palaeogeography, Palaeoclimatology, Palaeoecology DOI: 10.1016/j.palaeo.2012.06.024
December 7, 2011
Almost a century ago, skilled fossil collectors Charles H. Sternberg and his son Levi excavated a previously unknown horned dinosaur. Paleontologists didn’t realize the importance of the discovery until now.
The long-lost dinosaur was sitting right underneath paleontologist’s noses for decades. In 1916, while under commission to find exhibit-quality dinosaurs for what is now London’s Natural History Museum, the Sternbergs discovered and exhumed a dinosaur bonebed in the northwestern part of what is now Dinosaur Provincial Park in Canada. Among the haul were several portions of a ceratopsid skull. Some parts, such as the upper and lower jaws, were missing, but portions of the frill and a piece preserving the nasal horn, eye sockets and small brow horns were recovered. Although there was apparently not much to go on, the Sternbergs thought this dinosaur might be a new species closely related to the many-horned Styracosaurus.
Authorities at the London museum were unimpressed with what the Sternbergs sent over. Museum paleontologist Arthur Smith Woodward wrote to the Sternbergs that their shipment from the ceratopsid site was “nothing but rubbish.” As a result, the fossil collection was shelved and left mostly unprepared for 90 years. The museum had no idea there was a new dinosaur collecting dust. It wasn’t until 2004, when Raymond M. Alf Museum of Paleontology scientist Andrew Farke was rummaging through the museum’s collections during a visit, that the long-lost dinosaur was rediscovered.
We hear plenty about the struggles and adventure of digging up dinosaurs in the field. We hear far less about those finds that had been hidden away in museum collections—important specimens of already-known dinosaurs or previously-unknown species. I asked Farke how he rediscovered what the Sternbergs had found so long ago:
I first saw the specimen back in 2004, when I was over in the U.K. filming for “The Truth About Killer Dinosaurs.” I had a few hours to myself, so I arranged for access to the collections at the Natural History Museum. In browsing the shelves, I ran across these partially prepared ceratopsian bones. The thing that really caught my eye was this piece of the frill—the parietal bone. It was upside down and embedded in rock and plaster, but I saw what looked like two spikes sticking out the back of it. My first thought was that it was Styracosaurus, but something just didn’t look right. Could it possibly be a new dinosaur?! I spent a long time trying to convince myself that it was just a funky Styracosaurus, or that I was misinterpreting the bones. When I got back home, I chatted with Michael Ryan about it, and he was very surprised to hear about it too. Apparently it was this legendary specimen—Phil Currie had snapped a photo of it back in the 1980s, and Michael hadn’t been able to relocate it when he visited London himself. One way or another, I was the first person to relocate and recognize the fossil. So, we contacted Paul Barrett (dinosaur curator at the NHM), and Paul was able to arrange to get the specimen fully prepared.
When the dinosaur was fully prepped and studied by Farke, Ryan and Barrett with colleagues Darren Tanke, Dennis Braman, Mark Loewen and Mark Graham, it turned out that the Sternbergs had been on the right track. This Late Cretaceous dinosaur truly was a previously unknown animal closely related to Styracosaurus. The paleontologists named the animal Spinops sternbergorum as a reference to the dinosaur’s spiny-looking face and as a tribute to the Sternbergs.
Rather than being something wildly different, Spinops looks rather familiar. As Farke put it, this centrosaurine dinosaur “is like the love child of Styracosaurus and Centrosaurus,” the latter being a common horned dinosaur with a deep snout, large nasal horn, small brow horns and distinctive frill ornamentation. Whereas Spinops is like Centrosaurus in having two, forward-curving hooks near the middle of the frill, Farke notes, the two large spikes sticking out of the back of the frill in Spinops are more like the ornaments of Styracosaurus. Given these similarities, it might be tempting to think that the dinosaur just named Spinops was really just an aberrant Centrosaurus or Styracosaurus, but this doesn’t seem likely. “[W]e have two specimens of Spinops that show the same frill anatomy,” Farke says, “so we can be confident that this is a genuine feature and not just a freak example of Styracosaurus or Centrosaurus.”
Nor does Spinops appear to be just a growth stage of a previously known dinosaur. Over the past few years there has been a growing debate among paleontologists about the possibility that some dinosaurs thought to be distinct species were really just older or younger individuals of species that were previously named. (The idea that Torosaurus represents the skeletally mature form of Triceratops is the best-known example.) Horned dinosaurs, especially, have come under scrutiny in this lumping/splitting argument, but Spinops seems to be the real deal. Farke explains, “We have excellent growth series for Styracosaurus and Centrosaurus (the two closest relatives of Spinops), and nothing in their life history looks like Spinops—young or old. There’s no way to “age” Spinops into an old or young individual of another known horned dinosaur.”
This has significant implications for our understanding of how many dinosaurs were running around in the Late Cretaceous of what is now Canada. According to Farke, there are now five known species of centrosaurine dinosaurs within the series of rocks containing the Oldman Formation and Dinosaur Park Formation (spanning about 77.5 million to 75 million years ago). Not all of these dinosaurs lived beside each other at the same time, though, and determining exactly where Spinops fits is difficult because paleontologists have been unable to relocate the Sternberg quarry. Paleontologists are still trying to do so. A combination of fossil pollen from the rock Spinops was preserved in and historical documentation have allowed paleontologists to narrow down the area where Spinops was probably excavated, and Farke says he’s “cautiously optimistic that [the quarry] will be relocated—maybe not tomorrow, but hopefully in the next few decades.”
Pinning down where Spinops came from and exactly when it lived will be important to understanding how horned dinosaurs evolved during the Late Cretaceous. Such geological resolution would allow paleontologists to investigate whether Spinops was close to the ancestral line of Styracosaurus or was a more distant relative, Farke said. Perhaps continued prospecting will even turn up new specimens of Spinops from other locations. “We know the general area and rock level where Spinops came from,” Farke explained. “I think it’s just a matter of time and fossil collecting to find more!” Additional fossils would certainly be welcome, especially because there are plenty of questions about what Spinops means for our understanding of centrosaurine evolution. As Farke and co-authors lay out at the conclusion of the new paper, questions such as “Do the ceratopsians preserved here document anagenesis or cladogenesis [changes within a lineage or between lineages]? How are the taxa of Alberta related to those from elsewhere? Was Spinops a rare element of the Campanian fauna, or will more remains be recognized?” remain to be answered.
For me, at least, the discovery of a new ceratopsid dinosaur is always cause for celebration. Sadly, though, some of the media coverage of this well-ornamented dinosaur has been less than stellar. Gawker led in with “Moron paleontologists find new species of dinosaur in their own museum.” At least when they decide to miss the point, they really commit to that approach. Whatever scientific content there is in the news is overwhelmed by meanspirited snark, although, as some folks pointed out when I expressed my frustration about the piece on Twitter last night, Gawker is meant to be a joke site. Fair enough. In that case, getting your science news from them is about as productive as asking your friend who lives in a symbiotic relationship with the couch and is fueled almost entirely by Mr. Pibb for dating advice.
Juvenile snark is one thing. Trotting out the old “missing link” mistake is another. The Huffington Post fell into that trap when they ran their story “Spinops Sternbergorum: New Dinosaur Species Discovered, Could Be Missing Link.” *Facepalm* First off, there is presently no way to know whether Spinops was ancestral to any other kind of dinosaur. Farke and colleagues were able to determine the relationships of the new dinosaur compared to those already known—that is, they could tell who is more closely related to whom—but dinosaur paleontologists typically draw ancestor-descendant ties only in the case of exceptional and well-constrained evidence. In this case, especially, Farke and co-authors reject the hypothesis that Spinops was an intermediate form between Centrosaurus and Styracosaurus, and the scientists emphasize caution in hypothesizing about the relationships of Spinops to these dinosaurs until more data is found. The “missing link” hook is entirely unwarranted. Furthermore, the phrase “missing link” is closely tied to a linear view of evolution that obscures the deep, branching patterns of change over time, and there’s even a basic semantic issue here. When paleontologists find what the uninformed call a “missing link,” that link is no longer missing!
Media blunders aside, Spinops surely was a funky looking dinosaur, and the centrosaurine’s discovery emphasizes the role collections can play in our growing understanding of dinosaurs. There are far more dinosaur specimens than paleontologists, and there are still plenty of field jackets and specimens that have been left unprepared. Who knows what else is out there, waiting to be rediscovered? There is certainly an air of romance about fieldwork and hunting down dinosaurs, but there are surely fascinating, unknown dinosaurs hiding in plain sight.
Farke, A.A., Ryan, M.J., Barrett, P.M., Tanke, D.H., Braman, D.R., Loewen, M.A., and Graham, M.R (2011). A new centrosaurine from the Late Cretaceous of Alberta,
Canada, and the evolution of parietal ornamentation in horned dinosaurs Acta Palaeontologica Polonica : 10.4202/app.2010.0121
February 5, 2009
Every dinosaur enthusiast can immediately recognize Triceratops by its bony frill and three horns, but what did it actually use those horns for? The horns might have been used for defense against predators, for display, in combat between rival Triceratops, or even all three, but it has been difficult to find ways to test these ideas. In a new study published in the journal PLoS One, however, researchers found some tell-tale clues of ancient combat.
In 2004 paleontologist Andrew Farke, who writes the blog The Open Source Paleontologist, used scale models of Triceratops to see if two fighting individuals could effectively lock horns with each other. The models suggested that they could, but Farke needed more evidence that these dinosaurs were actually exhibiting these behaviors. To find these clues Farke teamed up with his colleagues Ewan Wolff and Darren Tanke and looked at the differences between the skulls of Triceratops and another kid of horned dinosaur, Centrosaurus.
The scientists found that both genera of dinosaurs had bone lesions around their frills, but Triceratops had significantly more on the squamosal bone (which makes up the base of the frill). There was no sign that these lesions were caused by disease or by the attack of a predator, but they were consistent with the idea that individual Triceratops fought each other by locking horns. (Centrosaurus did not have these pathologies, then, because it did not have large brow horns to fight with. If individual Centrosaurus fought each other they would be doing so in a different way.) These dinosaurs still may have used their horns for defense and display, but in Triceratops, at least, there is now evidence that horns played an important role in intraspecies conflict.
As Farke notes in his own summary of the paper, this research raises some interesting questions. Centrosaurus is thought to have evolved from an ancestor with Triceratops-like brow horns. If so, the shift in horn arrangement may have been reinforced by a change in one-on-one dinosaur combat that resulted in fewer injuries.