June 22, 2012
There has never been a better time for dinosaurs. Skeleton by skeleton, museum by museum, the reconstructed frames of the prehistoric creatures are being updated and repositioned in shiny displays garnished with interactive screens and smartphone tours. The last of the tail-dragging holdouts – leftovers from before the “Dinosaur Renaissance” of the 70s and 80s changed our perspective of how a dinosaur should look – are being disassembled and reconstructed in more active, agile positions. Among the latest museums to revamp their dinosaur exhibits is California’s Natural History Museum of Los Angeles.
The museum’s new dinosaur hall opened last July. I spent a day among the new exhibits a few months later. On the September day I visited, the windows encircling the hall let incoming sunlight wash over the skeletons and cast their shadows over the floor. This was quite different to the dark, dusty displays I encountered as a child, and more akin to the open, bright aesthetic New York’s American Museum of Natural History developed when they renovated their dinosaur halls in the late 90s.
Unlike the AMNH displays, which were arranged as an evolutionary tree of dinosaurs, the Los Angeles museum doesn’t seem to have any discernible floorplan. An elegant, ostrich-like Struthiomimus skeleton greets visitors to the lower gallery, while, just behind the mount, an Allosaurus harasses a Stegosaurus. The exhibit’s centerpiece – a three-part Tyrannosaurus growth series, from juvenile to young adult – looms nearby. From there the lower gallery displays continue on, past the shovel-beaked Edmontosaurus skull I recently wrote about and the resurrected frame of a stalking Carnotsaurus, before taking a turn into a larger room where models of the small, bristle-tailed dinosaur Fruitadens mingle with the skeletons of Mamenchisaurus and Triceratops. With the exception of a small subsection devoted to marine reptiles that lived at the same time as dinosaurs, the displays are not organized according to chronology, ecology, or evolution. Each is a little island to itself.
Upstairs is a different story. While the lower gallery is full of skulls and reconstructed skeletons, the exhibit’s upper floor is not as densely-populated by fossils. That’s a good thing. Downstairs visitors get to see the products of paleontology – genuine specimens and reconstructed hypotheses of what dinosaurs were like – but the top floor takes greater care to explain the science of what we know. The interactive displays explore the basics of fieldwork – with an amusing tabletop game that asks you to make decisions about how to spend a day in the badlands – and various aspects of dinosaur biology, including pathologies and senses. And, in a nice touch, the upper gallery empties out into a small alcove where a few of California’s local dinosaurs are displayed. Almost every dinosaur exhibit makes room for Tyrannosaurus, but I think it’s especially important to show off local prehistoric notables to help local visitors understand just how much their home state has changed through the course of time.
Paleontologist Andrew Farke published a review of the same exhibits in the latest Journal of Vertebrate Paleontology issue. Farke was just as impressed as I was by the stunning visual displays, but came away with the same concern:
The exhibits make abundantly clear that dinosaurs and their aquatic counterparts were living, breathing animals, but in what context? Many of the most eye-catching sections in the Hall of Dinosaurs feel as if they’ve been yanked out of space and time, with little sense for how the organisms fit within their ancient ecosystems or the tree of life.
Dinosaurs are not only wonderful creatures to gawk at. Any dinosaur skeleton is a snapshot of evolution, ecology, and extinction – a thread we can follow back through time to understand the world as it once was. The NHMLA deserves credit for creating beautiful displays and showcasing a few of the ways we can extract delicate details from ancient bones, but, without their essential evolutionary context, the hall’s dinosaurs can easily be cast as prehistoric monsters that have no relevance to the modern world. We know that isn’t the case. Our mammalian ancestors and cousins evolved alongside dinosaurs, and, as one small display points out, dinosaurs live among us today as birds. The “Age of Dinosaurs” and “Age of Mammals” have always been the same – the earliest mammaliformes evolved around the same time as the first dinosaurs, and dinosaurs, in avian garb, are a beautiful part of our modern world. If we don’t highlight our connection to dinosaurs through time and evolution, we may let the magnificent creatures slowly slip away from us and turn into irrelevant, hoary monsters.
Post-Script: Paleontologist Jack Horner just happened to be visiting the same day I wandered the museum galleries. The museum’s fuzzy Tyrannosaurus puppet came out to greet Horner, and the paleontologist shook hands with the tiny tyrant. [Horner is the man in green in the video below]
December 15, 2011
When the “Toroceratops” controversy broke in the summer of last year, I felt sorry for Nedoceratops. Hardly anyone said a word about this unusual horned dinosaur. Fans of Triceratops wept, wailed, and gnashed their teeth at their misapprehension that Museum of the Rockies paleontologists John Scannella and Jack Horner had exterminated the beloved horned dinosaur while paleontologists wondered if this dinosaurian mainstay of the Late Cretaceous could have grown into what had previously been called Torosaurus. But no one shed a tear at the proposition that Nedoceratops, too, might have been just a growth stage of Triceratops.
Known from a solitary skull on display at Smithsonian’s National Museum of Natural History, Nedoceratops has perplexed paleontologists since it was first described more than 100 years ago. The skull was found from the same end-Cretaceous strata that yielded Triceratops and Torosaurus, yet the dinosaur eventually labeled Nedoceratops was different from both. The skull had the general Triceratops-Torosaurus shape, but was distinguished by the lack of a nasal horn, a small opening in the preserved parietal portion of the frill, and two asymmetrical holes in the wing-shaped squamosal bones which made up the border of the frill. (These holes were thought to be old battle scars from some Cretaceous clash, but later studies showed these unusual perforations to be natural parts of the animal’s bone growth.) Scannella and Horner disagreed. Some of the unusual features, such as the apparent absence of a nasal horn, fell within the expected variation of Triceratops, and they interpreted the small hole in the parietal to be an early stage of the larger, rounded openings seen in the elongated frills of Torosaurus. Therefore, Scannella and Horner proposed, the Nedoceratops skull was a dinosaur virtually caught in the act of transitioning between the traditional Triceratops and Torosaurus forms, linking all three animals together into a single, late-life growth series.
Andrew Farke, a ceratopsian expert at the Raymond M. Alf Museum of Paleontology, came to a different conclusion when he published a reanalysis of the Nedoceratops skull earlier this year. The mix of features exhibited by Nedoceratops distinguished the dinosaur from both Triceratops and Torosaurus, Farke argued, which would remove the form with transitional features from the growth series. More than that, Farke offered up additional criticisms of the growth series Scannella and Horner proposed—Torosaurus might not be sunk, after all.
Now Scannella and Horner have published a response to Farke’s response. To an outsider, this might look like an echo of the 19th century “Bone Wars,” when the cantankerous naturalists Edward Drinker Cope and Othniel Charles Marsh battled each other in print over the proper identification and interpretation of dinosaurian remains. The headline for LiveScience’s report on the new paper states that the “debate rages,” though the argument is probably better cast of a difference of opinion that has generated some friendly competition. Farke and Scannella are close colleagues, and as Farke mentioned in a behind-the-scenes post on his Nedoceratops work, the paleontologists have helped critique and strengthen each other’s arguments prior to publication. The paleontologists are not about to assault each other at the next Society of Vertebrate Paleontology meeting, either.
Despite the collegiality between the parties, however, Scannella and Horner object to Farke’s critique. For one thing, the Montana-based researchers argue, each of the seemingly unique features of Nedoceratops can be found within the variation of Triceratops (which they count as including Torosaurus-type animals). Though Triceratops is classically portrayed as being a “three-horned face,” when I asked about the apparently absent horn of Nedoceratops, Scannella pointed out that “there are many Triceratops specimens which show similar low, subtle nasal ornamentation—not quite to the degree seen in ‘Nedoceratops’ but certainly approaching that state.” Alternatively, the nasal horn of Nedoceratops might have been broken off or lost after death since the horn does not actually fuse to the nasal bones until late in life. At the moment no one knows for sure whether the horn was lost or was simply never there, but Scannella emphasizes that none of these scenarios hinders the idea that Nedoceratops might be better categorized as a Triceratops.
And that’s not all. Some of the features thought to mark the Nedoceratops skull as an old individual that had finished growing are ambiguous, Scannella and Horner say. The rough bone texture and fusion between certain skull bones—thought to be indicators of maturity, and even old age—are variable in Triceratops and don’t necessarily represent the age range of the animal accurately. They uphold their original interpretation of the dinosaur as a Triceratops, and I have to admit that I was amused that Scannella and Horner pointed out that Nedoceratops translates to “insufficient horned face” in their paper. Though this refers to the apparent lack of a nasal horn, there is a certain poetic justice to it in a paper which seeks to sink the name. “I think ‘insufficient horned face’ is a very appropriate name given that the genus likely represents variation within Triceratops,” Scannella said.
Scannella and Horner offer an explanation for the slit-like opening on one side of the specimen’s frill. (The completed Nedoceratops skull on display was partially reconstructed, so we don’t know for sure if there was a matching hole on the other half.) The projected sequence of transformation from Triceratops to a Torosaurus-type form predicts that there would be a stage in which the solid frill of Triceratops would develop depressions or holes that would eventually open to create large, circular fenestrae. Scannella explains the transformation happening like this:
As Triceratops matured, the parietal developed increasingly thin areas which eventually formed the holes previously thought to be characteristic of “Torosaurus.” If you take a typical Triceratops with a thick, solid frill and have it undergo this transformation to “Torosaurus,” there’s going to come a point where the parietal is going to begin to develop openings. These openings will likely start off rather small and continue to grow as resorption continues and the parietal expands. This is what we see in “Nedoceratops“—it’s a fairly mature specimen, the squamosals are slightly elongate (approaching the morphology observed in “Torosaurus“), and the parietal has a small opening in the same place where in Triceratops we see thinning occurring and in “Torosaurus” we see holes. So—one possibility is that this is a distinct genus of dinosaur that has tiny holes in its parietal. Another is that this is simply a Triceratops caught in the act of becoming “Torosaurus.” Jack and I favor the hypothesis that “Nedoceratops” is actually a transitional morphology, between Triceratops and “Torosaurus.”
One of the areas of debate has been the number of triangular, bony ornaments called epiossifications around the border of the Triceratops frill, which is composed of the parietal and squamosal bones. Previous studies have established that these bones start off being prominent, pointed ornaments, but as Triceratops aged these bones flattened out until they were barely visible. The question is whether the number of some of these epiossifications could change during growth, thus bridging the gap between the different number of these ornaments on the parietals of Triceratops and Torosaurus.
While Triceratops typically has five or six of these bones, called epiparietals, Torosaurus have been found with spots for 10 to 12, requiring the number to double if Scannella and Horner are right. This kind of addition has not been seen in well-sampled populations of horned dinosaurs before, but Scannella and Horner propose that such changes were indeed possible. As evidence, they cite a single epiossification marked by two peaks, which they hypothesize is an ornament in the process of splitting into two. Additional specimens will be needed to determine whether this double-peaked adornment truly was splitting during a transformative growth stage or is an unusual and unique variant. While Farke cautions that he hasn’t seen the specimen in question himself, he does offer an alternative interpretation. The double-peak shape “could also just be resorption of the tip without splitting a single element into two,” he says. “This is relatively common in ceratopsids—many of them tend to resorb the tips of the ‘high points’ on the skull, and that may be what is happening here.” If this is the case, then the epiossification would be part of the typical transformation into flatter adornments and not indicative of splitting.
This aspect of debate brings up the question of how useful epiossification counts might be for identifying distinct ceratopsids in the Hell Creek Formation. Individual variation, changes in growth and possibly even variation from one slice of time to the next might complicate matters. “As we are finding more and more Triceratops in the Hell Creek Formation of Montana,” Scannella says, “we are seeing specimens with quite a bit of variation in both the number and position of frill epiossifications–a finding which urges caution before considering epiossification number and position a set in stone indicator of taxonomic identity, at least in taxa closely related to Triceratops.” Farke takes a different view. “[Scannella and Horner are] almost certainly correct that there is stratigraphic variation in epiossification count (presumably related to evolutionary change in a lineage),” he says, but points out that “This would strengthen the argument that epiossification count has phylogenetic significance … [I]f early Torosaurus have one count and late Torosaurus have another count, this would suggest that this trait changes through time and we can use epiossification count to distinguish different species.” Though all this argument over ceratopsid ornaments might seem esoteric, it is a key part of the discussion over what Nedoceratops and Torosaurus truly were. Did some ceratopsid dinosaurs add—and even double— frill ornaments as they matured? The answer to that question will have a major influence on the future of this debate.
What was Nedoceratops? That still depends on who you ask, and there is more than one possible answer. Farke, while noting that “Scannella and Horner raise some valid critiques of my diagnosis of Nedoceratops” in the new paper, still doesn’t see the dinosaur as an intermediate growth stage. “[W]e do still disagree on the taxonomic relevance of things like the parietal fenestrae,” Farke says. “[T]hey cite [the fenestrae] as transitional morphology between the Triceratops-morph and the Torosaurus morph of a single animal’s growth trajectory, whereas I would posit it as the end-member morphology for whatever Nedoceratops is.” And these aren’t the only options. “Of course, Nedoceratops might be an unusual or pathological individual of Triceratops. I’m not particularly married to any hypothesis at this point,” Farke says.
If Nedoceratops is an intermediate growth stage between the classic Triceratops and Torosaurus body types, further sampling of the Hell Creek and Lance Formations should eventually turn up still-growing Triceratops with similar features. Then again, if Nedoceratops is a distinct genus we would expect to eventually find juvenile individuals which share specific features with the single known skull to the exclusion of Triceratops and Torosaurus. Or maybe Nedoceratops is just a weirdo Triceratops.
This isn’t just a bit of paleontological arcana. The scientific conversation about Triceratops growth emphasizes the difficulties of recognizing prehistoric species and understanding their biology. What were once considered to be different species may just be growth stages or variants of one dinosaur, and these revisions affect our understanding of dinosaur evolution, biology, and ecology. I asked Scannella for his thoughts on the implications for his hypotheses, particularly given the fact that many dinosaurs are known from single, and often partial, specimens:
Increasingly, we are learning that many skeletal features in a wide variety of dinosaurs change throughout development. There is also individual variation to consider. If all the differences between specimens are considered taxonomically informative, then it is easy to see how 16 species of Triceratops were named based on small differences in cranial morphology. Dinosaurs changed as they grew—and so, we need to evaluate which features are the most taxonomically informative. This can be hard to do if there is only one specimen of a particular dinosaur. We can start by examining developmental trends in dinosaurs thought to be closely related to that one specimen – as we’ve done with “Nedoceratops.” Examination of the bone microstructure is also important, in order to get an idea of relative maturity.
Paleontologists have recognized the problems of identifying slightly different specimens as new species before, but the debate over Triceratops—as well as Tyrannosaurus, Pachycephalosaurus, and other Hell Creek dinosaurs—has helped reinvigorate interest in how little dinosaurs grew up. Paleontologists are still in the relatively early phases of this investigation, and there are far more questions than there are definitive answers. The clues that will resolve the question of whether Triceratops was the lone ceratopsid of the Hell Creek still wait in museum collections and the expansive fossil graveyard that is the badlands.
Farke, A. (2011). Anatomy and Taxonomic Status of the Chasmosaurine Ceratopsid Nedoceratops hatcheri from the Upper Cretaceous Lance Formation of Wyoming, U.S.A PLoS ONE, 6 (1) DOI: 10.1371/journal.pone.0016196
Scannella, J., & Horner, J. (2010). Torosaurus Marsh, 1891, is Triceratops Marsh, 1889 (Ceratopsidae: Chasmosaurinae): synonymy through ontogeny Journal of Vertebrate Paleontology, 30 (4), 1157-1168 DOI: 10.1080/02724634.2010.483632
Scannella, J., & Horner, J. (2011). ‘Nedoceratops’: An Example of a Transitional Morphology PLoS ONE, 6 (12) DOI: 10.1371/journal.pone.0028705
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
June 13, 2011
In the novel Jurassic Park, the fictional scientists of the InGen corporation tried to cook up a batch of dinosaurs using fragments of DNA preserved in Mesozoic mosquito blood. An inventive idea, certainly, but not one that would actually work. In the wake of the book’s blockbuster film adaptation, though, paleontologist Robert Bakker commented that there might be another way to make a dinosaur, or at least something dinosaur-like. Birds, after all, are the living descendants of dinosaurs, and by fiddling with the genetic toggles of living birds, scientists might be able to reverse-engineer a dinosaurian creature.
Now, 18 years later, the “chickenosaurus” project is actually underway, but under the guidance of another well-known paleontologist. Two years ago Jack Horner published his outline of the project with writer James Gorman in the book How to Build a Dinosaur, and he recently provided an overview of the project at a TED talk in Long Beach, California. (Horner also delivered a TED lecture in Vancouver, but on the growth stages of dinosaurs.) The goal isn’t to perfectly re-engineer a Deinonychus or other dinosaur—that is impossible. Instead, Horner wants to use this project to investigate the role of genes and development in evolution, with the resulting creature acting as a “poster chick” for scientific investigation. Maybe a long-tailed chicken with teeth won’t satisfy those who dream of owning a pet dinosaur, but at the very least, the science might tell us something about how living dinosaurs—that is, birds—originated.
May 24, 2011
Are there too many dinosaurs? Paleontologist Jack Horner thinks so, and he explained his reasoning in a short TED talk last month in Vancouver, Canada.
Over the past several years, Horner has been picking over the skeletons of Late Cretaceous dinosaurs from North America in an attempt to figure out whether some of the dinosaurs labeled as distinct species are actually growth stages of a single species. In 2009, for starters, Horner and Mark Goodwin proposed that the dome-headed dinosaurs Dracorex and Stygimoloch were actually immature representatives of the larger Pachycephalosaurus. Last year, Horner and colleague John Scannella made a bigger splash when they published a Journal of Vertebrate Paleontology paper suggesting that the broad-frilled, horned dinosaur Torosaurus was the adult stage of Triceratops (though this hypothesis has been contested). In the video, Horner also suggests that the hadrosaur Edmontosaurus was the subadult stage of the larger Anatotitan.
This kind of revision isn’t new. Many dinosaurs specimens that were once thought to be pygmies or oddly-proportioned adults of new species have turned out to be juveniles, such as the diminutive sauropodomorph Mussasaurus, hadrosaur specimens previously assigned to “Procheneosaurus,” and the ever-contentious Nanotyrannus. What’s different now is that paleontologists have more powerful techniques to investigate and compare specimens from well-sampled areas. Scientists can now look into the bone itself to estimate age, for example, allowing researchers to see if a seemingly small form was truly an adult or still had a bit left to grow.
I wouldn’t say that we have too many dinosaurs, though. Many new species are coming from areas that have not been previously explored or are poorly understood. Given how little we know about the past and how few paleontologists there are,many, many dinosaurs are undoubtedly yet to be discovered. These new species will be subjected to in-depth scientific investigations and in time, paleontologists will gain a deeper understanding of how dinosaurs grew up.
For another take on the same video, check out Love in the Time of Chasmosaurs.