December 7, 2012
When paleontologist John Ostrom named Deinonychus in 1969, he provided the spark for our long-running fascination with the “raptors.” Similar dinosaurs had been named before–Velociraptor and Dromaeosaurus were named four decades earlier–but the skeleton of Ostrom’s animal preserved a frightening aspect of the dinosaur that had not yet been seen among the earlier finds. The assembled remains of Deinonychus included the dinosaur’s eponymous “terrible claw”–a wicked, recurved weapon held off the ground on the animal’s hyperextendable second toe. Combined with the rest of the dinosaur’s anatomy, Ostrom argued, the frightening claw indicated that Deinonychus must have been a active, athletic predator.
But how did Deinonychus and its similarly-equipped relatives use that awful toe claw? The appendage looks fearsome, but paleontologists have not been able to agree on whether the claw was using for slashing, gripping, pinning, or even climbing prey. Some researchers, such as Phil Manning and collaborators, have even argued that the claws of Velociraptor and related dinosaurs were best suited to scaling tree trunks–a conclusion consistent with the contentious hypothesis that the ancestors of birds were tree-climbing dinosaurs.
All this assumes that the claws of deinonychosaurs correspond to a special behavior, but can foot claw shapes really give away the habits of dinosaurs? That’s the question posed by a new PLoS One study by zoologist Aleksandra Birn-Jeffery and colleagues.
Based on observations of living animals, researchers have often tied particular claw shapes to certain behaviors–relatively straight, stubby claws likely belong to an animal that runs on the ground, while tree-climbing species have thin claws with small, sharp points. But nature isn’t quite so neat as to have a single, tell-tale claw shape for perchers, ground-runners, climbers, and predators. Even then, researchers don’t always interpret claw shapes the same way–depending on who you ask, the foot claws of the early bird Archaeopteryx either indicate that it was a climber or could only run on the ground.
To parse this problem, Birn-Jeffery and co-authors studied the geometry of the third toe claw–on dinosaurs, the middle toe claw–in 832 specimens of 331 species, together representing different lifestyles of birds, lizards, and extinct dinosaurs. The claw shapes didn’t strictly conform to particular behaviors. In the climber category, for example, the frill-necked lizard has lower claw curvature than expected, and, among predatory birds, the common buzzard, secretary bird, and greater sooty owl has less sharply recurved claws that anticipated for their lifestyle.
When the dinosaur data was dropped into the mix, the deinonychosaurs didn’t seem to fit in any single category. The sickle-clawed carnivores fell into the range shared by climbers, perchers, predators, and ground dwellers–these dinosaurs could be said to be anything from wholly terrestrial runners to perchers. And even though the researchers identified a general claw shape that corresponded to walking on the ground–deeper claws with less curvature–the dinosaurs did not strictly fit into this category alone.
Some dinosaurs, such as Microraptor, had claws that might have been suited to climbing. However, dinosaurs that we might regard as behaviorally similar showed differences–Velociraptor seemed to best fit the ground-dweller category, while the larger Deinonychus seemed to have claws more akin to those of predatory birds. This doesn’t mean that Microraptor was definitely a climber, or that Velociraptor wasn’t a predator. As the authors show, the different behavioral categories are not so easily distinguishable as previously thought, and saying that an animal definitely engaged in a particular behavior because of claw shape alone tempts oversimplification.
No wonder there has been such a range of interpretation about dinosaur foot claws! While the new study focused on the third toe claw rather than the famous, second deinonychosaur toe claw, the point of the analysis still applies. Claw geometry alone is not a reliable indicator of behavior. That’s to be expected–as the authors point out, claws are multi-functional, are are unlikely to represent just one type of behavior or habitat. Birds that use their claws to perch may also use them to kill prey, or birds that primarily live in the trees may also forage on the ground. Claw shape is constrained by different aspects of natural history, and reflect flexibility rather than strict adherence to a particular lifestyle. Deinonychosaur claws definitely hold clues to the natural history of dinosaurs, but drawing out those clues is a difficult, convoluted process.
Birn-Jeffery, A., Miller, C., Naish, D., Rayfield, E., Hone, D. 2012. Pedal Claw Curvature in Birds, Lizards and Mesozoic Dinosaurs – Complicated Categories and Compensating for Mass-Specific and Phylogenetic Control. PLoS ONE. 7,12: e50555. doi:10.1371/journal.pone.0050555
November 22, 2012
Tonight, at dinner tables all around the country, families are going to dine on dinosaur. If you dissect your holiday theropod just right, the ancient nature of the tasty avian is strikingly evident–right down to the wishbone. But what kind of dinosaur is a turkey, anyway?
Birds are dinosaurs. That’s a fact. But birds are really just one kind of dinosaur. Indeed, we call Triceratops, Euoplocephalus, Futalognkosaurus, Allosaurus and their ilk non-avian dinosaurs because these lineages fell outside the bird subgroup at greater or lesser distances. Birds are a distinct form of dinosaur, nested within a great group of fuzzy and feathery forms.
Let’s start from the bottom up. The dinosaur family tree is divided into two major branches–the ornithischians (the ceratopsids, hadrosaurs, stegosaurs and their relatives) and the saurischians. The saurischian side is made up of the long-necked, big-bodied sauropodomorphs and the bipedal, often-carnivorous theropods. The theropod subset is further subdivided into various groups, one of the major ones being the coelurosaurs. This subset includes the the famous tyrannosaurs, ostrich-like ornithimomosaurs, odd-looking oviraptorosaurs, sickle-clawed deinonychosaurs and birds, among a few others. Every lineage within this group contained at least one representative with feathers, and many of these dinosaurs were quite bird-like both anatomically and behaviorally.
Now here’s where things get tricky. For decades, numerous anatomical characteristics seemed to link the earliest birds, represented by Archaeopteryx, with deinonychosaurs similar to Velociraptor and Troodon. But some paleontologists have questioned this hypothesis. Last year, a controversial Nature paper suggested that the resemblance was because Archaeopteryx wasn’t actually a bird but a non-avian dinosaur more closely related to Deinonychus, while the first birds evolved from feathered dinosaurs akin to Oviraptor or the enigmatic Epidexipteryx. Rather than being deadly hypercarnivores, these alternative candidates for avian ancestry were oddball omnivores that often sported flashy tail feathers.
Not everyone agrees with the new proposal. For now, Archaeopteryx is still widely regarded to be at the base of the bird family tree, recently branched off from a deinonychosaur ancestor. Nevertheless, the argument underscores the point that many traits thought to be exclusively avian evolved much earlier in dinosaurian history than we previously expected. The more dinosaurs we find, the smaller the difference between the earliest avian dinosaurs and their non-avian ancestors. I know the pudgy kid in Jurassic Park called Velociraptor as “six foot turkey” as a put-down, but the comment isn’t too far of the mark. When you pick at the bird on your plate tonight, you’re devouring the dressed remains of a distant Deinonychus cousin.
August 31, 2012
Earlier this week, I got into a snit over the blinkered assertion that feathery dinosaurs are lame. I argued the opposite point–as I wrote at the time “Feathered dinosaurs are awesome. Deal with it.” How fortunate that a new paper this week offers proof of fuzzy dinosaur superiority. The evidence comes in the form of gut contents found within predatory dinosaurs that stalked Cretaceous China around 125 million years ago.
The carnivores in question are a pair of Sinocalliopteryx. These dinosaurs were close cousins of the much earlier Compsognathus, albeit quite a bit larger. While Compsognathus was turkey-size, about three feet long, Sinocalliopteryx grew to be about eight feet long. And this big predator was fluffy. The original description of the dinosaur mentioned the vestiges of simplified dinofuzz around the body of Sinocalliopteryx, and this makes sense given the dinosaur’s relationships. While considerably bigger than its close relatives, Sinocalliopteryx was a compsognathid–a group of theropod dinosaurs that also includes fuzzy forms such as Sinosauropteryx and Juravenator. Big or small, the compsognathids were hunters wrapped in wispy plumage.
And the initial description of Sinocalliopteryx mentioned something else. The skeleton that formed the basis of the original paper contained the leg of an unidentified dromaeosaurid dinosaur in its gut contents. Even though dromaeosaurids have long been cherished as sickle-clawed uber-predators, Sinocalliopteryx had clearly eaten the drumstick of one of the smaller feathered predators. Since then, paleontologists have identified a second Sinocalliopteryx with gut contents, and the two dinosaurs form the basis of a new PLoS One study by University of Alberta paleontologist Lida Xing and colleagues.
Looking back at the first Sinocalliopteryx, Xing and colleagues identified the victim as Sinosauropteryx. The second Sinocalliopteryx specimen had a different menu before it perished–its stomach contains the remains of two Confuciusornis, an archaic bird, and bones from an unidentified ornithischian dinosaur. But these gut contents invoke an aggravating mystery. Did these Sinocalliopteryx hunt their dinosaurian prey, or did they scavenge their meals?
This isn’t the first time paleontologists have puzzled over the meaning of predatory dinosaur gut contents. Earlier this year, Dave Hone and collaborators investigated a pterosaur bone found inside a Velociraptor, and last year Jingmai O’Connor and colleagues described a Microraptor with the remains of a bird in its gut (just to pick two examples of many). Frustratingly, though, it’s difficult to say how the dinosaurs obtained the meat. In the case of the Velociraptor, the researchers could not rule out hunting even though scavenging seemed the more likely option. Likewise, even though O’Connor and co-authors suggested their Microraptor hunted birds in the trees, the non-avian dinosaur could have just as easily scavenged a dead bird that fell to the forest floor. Gut contents tell us about what dinosaurs consumed, but they almost never provide direct evidence of how carnivores obtained flesh and bone to eat.
In the case of Sinocalliopteryx, the PLoS One study concludes that the dinosaur may have been skilled at catching live avian prey. The fact that one Sinocalliopteryx fed on two Confuciusornis in quick succession could mean that the large dinosaur was adept at nabbing early birds. “[T]he evidence of bird predation in Sinocalliopteryx,” Xing and colleagues conclude, “suggests that it was a highly capable stealth hunter.” Then again, the same researchers also note that their scenario “is speculative.” While it may seem improbable, the Sinocalliopteryx in question could have scavenged one or both of those birds, as well as the non-avian dinosaur remains in its stomach. We just don’t know. Like many predators, Sinocalliopteryx most likely hunted live prey and took advantage of carrion. Frustratingly, these fossil gut contents can’t tell us what happened in each case. Sinocalliopteryx may very well have been a skilled bird-slayer. Or perhaps not. The fact is that we don’t know for sure.
Perplexing feeding habits aside, there’s something else about the gut contents of Sinocalliopteryx that can give us a closer look at the dinosaur’s biology. In the dinosaur that ate the two birds and the ornithischian, the bone of the ornithischian dinosaur was corroded by stomach acid. The more delicate bird bones, by contrast, had not been so damaged. This means that the Sinocalliopteryx ate the ornithischian first, followed by one bird and, later, another. More than that, the acid damage indicates that at least some dinosaurs had highly-acidic foreguts where bone was broken down–comparable, but not exactly like, the stomachs of crocodilians and perhaps some bone-eating birds like the bearded vulture.
All of which is to say that Sinocalliopteryx is a great example of a fluffy dinosaur you wouldn’t want to mess with. Even if we can’t discern the backstory of each meaty morsel, the variety of prey in the Sinocalliopteryx stomachs shows that this dinosaur wasn’t a picky eater and may have even been a quick hunter that specializing in snapping up other feathery dinosaurs. For our fuzzy mammalian predecessors, hiding the Cretaceous forests, this would have been one scary dinosaur.
Xing L, Bell PR, Persons WS IV, Ji S, Miyashita T, et al. (2012) Abdominal Contents from Two Large Early Cretaceous Compsognathids (Dinosauria: Theropoda) Demonstrate Feeding on Confuciusornithids and Dromaeosaurids. PLoS ONE 7(8): e44012. doi:10.1371/journal.pone.0044012
August 7, 2012
It’s finally happening. After years of rumors, including speculation and consternation about Black Ops raptors, it seems that Jurassic Park 4 is actually going to happen. According to the latest news, writers Amanda Silver and Rick Jaffa are working on the script, and producer Frank Marshall has said that he’d like to see the film hit screens by the summer of 2014. That’s awfully soon, so I can only imagine that we’re going to be hearing a lot more about the fourth film in the dinosaur-filled franchise soon. The only thing we know for sure? Despite rumors that have been circulating for years, the sequel will not feature “weaponized dinosaurs.”
I’m of two minds about the news. I saw the first Jurassic Park film when I was ten, and it only concentrated my love of dinosaurs. I had never seen anything like it before, and I was shocked by how realistic the dinosaurs looked (especially compared to the stop-motion creatures that perpetually stampeded across basic cable monster movie marathons). I was young enough to enjoy the adventurous spirit of the second movie without thinking too much, and, like many others, I was let down by the third installment. Given the franchise left us on a sour note, and it has been almost a decade since Jurassic Park III came out, I have to wonder if we really should go back to those dinosaur-infested islands. Or, to paraphrase Ian Malcolm’s admonition from the first movie, perhaps the filmmakers should stop thinking about whether they could make another Jurassic Park and start thinking about whether they should.
Don’t get me wrong. If and when Jurassic Park 4 hits theaters, I’ll see it. I can’t stay away from silver screen dinosaurs. The question is whether the sequel is going to revive the franchise, or whether I’ll be sitting there in the dim auditorium, facepalming the whole time. The difference isn’t going to be in how much screentime the dinosaurs get, or how well-rendered they are, but how the filmmakers employ the dinosaurs.
Monsters only work if they mean something. There has to be something more to them than just their ability to eat you. Godzilla is iconic because he embodied the nuclear atrocities unleashed on Japan by the United States; Frankenstein was a tragic creature that reflected our fear of the unknown and the power of science; and the dinosaurs of the original Jurassic Park made us question whether the world is really ours, or was just ceded to us by a stroke a cosmic luck that wiped out Tyrannosaurus and friends. The second and third Jurassic Park films faltered because they forgot the symbolic power monsters hold–the dinosaurs simply became sharp-toothed aberrations that had to be escaped, and that’s all. The dinosaurs didn’t lead us to question or reexamine anything about how we interact with the world. If Jurassic Park 4 is going to outshine the other installments, its creators have to think of what dinosaurs mean, not just the devastation dinosaurs can cause.
Unless the writers, director and producers of the next installment have something truly original planned, maybe we should just let sleeping Velociraptor lie. The watered-down “don’t mess with nature” storyline of the first movie was standard moralistic claptrap, but that didn’t matter because audiences had never seen dinosaurs like that before. I was blown away when I saw the movie during opening weekend–Stan Winston and the assembled team of special effects artists had made the closest thing to living Tyrannosaurus and Velociraptor that I had ever seen. You can only pull that trick once. The franchise tried to spice things up with a second island, a scientific expedition, dueling egos and more imperiled children–Steven Spielberg’s favorite kind–in the following two movies, but, by the end, the series just felt tired. Despite all the effort put into envisioning and recreating the dinosaurs, the filmmakers seemingly had no idea what to do with them, and so we reverted to a big-budget version of the yarns I used to create with dinosaur toys in my sandbox as a child. If the dinosaurs don’t have a purpose–some lesson that they can teach us–then perhaps we should just leave them alone on their island.
Let’s be optimistic, though. I truly hope that the scribes behind the new story have something novel in mind. And I’m sure Universal knows all too well what can happen if sequels aren’t carefully planned. Look what happened to another blockbuster monster franchise spawned by Spielberg–JAWS. The first film is a classic, the second is acceptable popcorn fun, the third is a moronic gimmick film that’s still worth riffing on after a drink or two and the fourth is an abomination that will forever stain the career of Michael Caine. Spielberg was wise to duck out early. What else can you really do with a giant, human-chomping shark who relies on the stupidity of people to feed? I feel we’re approaching the same point with the Jurassic Park series, if we’re not there already. I adore dinosaurs–there’s no question of that–but I’d hate to see them brought back to life simply to be mindless Hollywood contrivances whose only role is to virtually menace our protagonists.
Provided that Marshall’s ambitious timeline is on the mark, we’ll see Jurassic Park 4 in a few years. All the same, I’d hate to see one franchise with a relatively narrowed set of storytelling options monopolize silver screen dinosaurs. The time is ripe for new ideas, or a more nuanced take on classic plots like the ever-useful “lost world” storyline. Why not give Ray Bradbury’s classic “A Sound of Thunder” another try (with some real effort this time, please) or, even better, expand S.N. Dyer’s “The Last Thunder Horse West of the Mississippi”, about what happens when 19th-century paleontologists E.D. Cope and O.C. Marsh race to capture the world’s last-surviving sauropod. There’s a vast literature out there, ready to be mined, not to mention whatever original ideas screenwriters might concoct. The point is this–rather than holding our breaths for another Jurassic Park, perhaps filmmakers should start exploring dinosaur tales that reflect our collective hopes and fears.
Dinosaurs will continue to roar and stomp across the screen for many years to come. Whether it’s in a Jurassic Park sequel, a comic book adaptation, a remake or something else, dinosaurs are too popular and bizarre to rest for long. They’re perfect monsters. What we should remember, though, is that the most wonderful and terrible monsters are the ones that help us put our world in context. In one way or another, they change the way we perceive our relationship with the world around us. Teeth and claws are their weapons, but, to be truly effective, those weapons have to be given a reason to inflict the awful damage they evolved to do.
August 1, 2012
Almost 20 years since it first debuted, Jurassic Park is still the quintessential dinosaur movie. But what if the Mesozoic and Cenozoic eras were flipped, with intelligent Velociraptor pondering the ferocity of our species? This YouTube parody imagines just that, and a follow-up cartoon depicts that dinosaurs’ amazement at seeing living elephants in “Quaternary Park.” I can only hope that the creators of the spoof eventually get to the famous chase sequence, with a tiger chasing after a jeep full of Velociraptor.