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.
September 6, 2012
Anyone who regularly reads this blog knows that there’s a very easy way to make me annoyed–all you have to do is start whining about how dinosaurs are less cool since paleontologists discovered that many non-avian species sported tufts and coats of fluff, fuzz, bristles and feathers. My reaction is usually along the lines of “Brian SMASH!” Even though I understand that some people find scaly, monstrous dinosaurs aesthetically appealing, I have no patience for the callow assertion that science has somehow ruined dinosaurs through the addition of plumage.
Cartoonist Randall Munroe summed up my feelings–albeit in a more concise and positive way–this week at XKCD. Restoring dinosaurs with protofuzz and feathers isn’t just about giving Tyrannosaurus, Velociraptor and company a new look. Dinosaur feathers, and feather-like structures, are allowing paleontologists to think of dinosaurs in new ways. In particular, Munroe cites a PLoS One study about how feathers may have played into the predatory behavior of sickle-clawed dromaeosaurs such as Deinonychus. According to paleontologist Denver Fowler and co-authors, Deinonychus may have used its famous “killing claw” to pin down small prey just like modern hawks and eagles do. More than that, the avian raptors flap to help stabilize themselves while immobilizing their prey, and Deinonychus–almost certainly a feathered dinosaur–may have done the same.
We can’t know for sure whether Deinonychus killed prey like a big, grounded version of a hawk. But it’s possible. Either way, though, studies like these show that prehistoric dinosaur feathers are allowing paleontologists to look to modern birds to generate new hypotheses and tease out previously-unknown aspects of dinosaur lives. As I’ve mentioned before, feathers are the key to figuring out dinosaur colors. How wonderful is that? Again, Munroe says it better than I can: “The past keeps getting cooler!”
Post script: Munroe isn’t the only cartoonist to take on dinosaurs this week. FoxTrot’s Bill Amend had a few suggestions for the Smithsonian National Museum of Natural History’s dinosaur hall renovation. Paleontology curator Matt Carrano responded to the idea of installing a “Tourist Chompsognathus” at our Around the Mall blog.
June 8, 2012
Prior to the summer of 1993, “raptor” was synonymous with “bird of prey.” If you said “raptor,” whoever you were talking to knew you were talking about some kind of hawk, owl, eagle or other sharp-taloned aerial predator. Then Jurassic Park came along. Thanks to some taxonomic muddling and abbreviation, the cunning, sickle-clawed villains of the film’s third act immediately came to be known as “raptors.” Velociraptor, Deinonychus and kin had stolen the term for themselves.
Among non-avian dinosaurs, raptor might refer to the entire group of feathery coelurosaurs with grasping hands and hyperextendable toe claws—the deinonychosaurs—or to a specific subset of that group, called dromaeosaurids. It depends on where you care to draw the line. Just like its use among avian dinosaurs, the word “raptor” is informal and is a quick way to draw a conceptual outline of any dinosaur similar to Velociraptor.
But not everyone is happy with how “raptor” has been co-opted. A few months ago, paleontologist and Tetrapod Zoology author Darren Naish wrote:
Oh, and can everybody please stop using the word ‘raptor’ as a popular term for deinonychosaur, or dromaeosaurid? Admittedly, this rarely causes confusion, but it looks dumb and naive given that THE WORD RAPTOR IS ALREADY IN USE FOR ANOTHER GROUP OF ANIMALS. It would be like deciding to call sauropods ‘elephants’ or something.
And earlier this week, a reader sent me an email questioning the Los Angeles Times‘ use of the word raptor to describe a new genus of dromaeosaurid found in the Early Cretaceous rock of Utah. If birds of prey had claim to “raptor” first, and the term is just a bit of pop culture fluff, should we drop the word and push for deinonychosaur instead?
I don’t think so. Even though some informal dinosaur terms make me cringe—such as “parasaur” for Parasaurlophus and “Trike” for Triceratops—I think “raptor” provides a useful hook. To borrow a bit from another Steven Spielberg monster flick, you say “deinonychosaur,” and people say “Huh? What?” You say “raptor,” and your audience immediately has a general image of what sort of dinosaur you’re talking about. Rather than lament the reapplication of the word raptor as misappropriation or dumbing down, we might as well take advantage of the instant recognition the word triggers when trying to communicate with people who are not up on the latest theropod phylogeny. Almost twenty years after Jurassic Park debuted, it’s a little late to put “raptor” back in the cage.
More than that, I think “raptor” is a perfectly wonderful term for dromaeosaurids, if not deinonychosaurs as a whole. Not only has the “raptor” suffix been used in numerous dromaeosaurid names—Velociraptor, Utahraptor, Bambiraptor, Pyroraptor, Microraptor and so on—but these feathery dinosaurs were close cousins of the lineage which spawned the first birds. Some dromaeosaurids may have even hunted like avian raptors, using their huge tow claws to pin down prey rather than slash at it. Since “raptor” was always an informal term that applied to various lineages of avian dinosaurs anyway, I think it’s perfectly legit to use the word for the more ancient, non-avian precursors of today’s formidable falcons and eagles. Avian and non-avian raptors were dinosaurs of a feather.
September 12, 2011
Long ago, I was told a simple rule about wine—if you’re not sure what you want, don’t pick up the bottle with the coolest looking animal on the label. That strategy is almost always a mistake. Or, as The Onion once put it, “The quality of a wine is inversely proportional to the viciousness of the animal depicted on the label.” Given my love of dinosaurs, though, I might have to overlook these truisms should anyone ever offer me a glass of Terra Fossil wine.
Sent in by reader Tim Goodwin, these (noticeably empty) bottles of dino wine were spotted at a Manhattan party. I had never heard of the brand before, but according to their website, Terra Fossil wines carry dinosaurs as a tribute to the rumor that fossil bones were once found on the Argentine vineyard where the wine’s grapes are grown. This could be true—many, many dinosaurs have been found in Argentina, including the sauropod Mendozasaurus from the same province as the vineyard.
As is too often the case, though, the dinosaurs on the labels aren’t quite anatomically accurate. The Apatosaurus drags its tail, the Tyrannosaurus takes up a Godzilla-like posture and, worst of all, poor Velociraptor has a bad case of “bunny hands” in which its wrists are broken so that its palms face downward instead of towards each other. The unfortunate dinosaur could not hold a glass of wine even if it wanted to.
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