December 14, 2012
There’s always something new to learn about dinosaurs. Whether it’s the description of a previously-unknown species or a twist in what we thought we knew about their lives, our understanding of the evolution, biology, and extinction is shifting on a near-daily basis. Even now, paleontologists are pushing new dinosaurs to publication and debating the natural history of these wonderful animals, but the end of the year is as good a time as any to take a brief look back at what we learned in 2012.
For one thing, there was an exceptional amount of dino-hype this year. A retracted paper that mused on the nature of hypothetical space dinosaurs, a credulous report on an amateur scientist who said he had evidence that all dinosaurs were aquatic, and overblown nonsense about dinosaurs farting themselves into extinction all hit the headlines. (And the less said about the Ancient Aliens dinosaur episode, the better.) Dinosaurs are amazing enough without such sensationalist dreck, or, for that matter, being transformed into abominable human-raptor hybrids by Hollywood.
Not all the dinosaurs to wander into the media spotlight were atrocious, though. The glossy book Dinosaur Art collected some of the best prehistoric illustrations ever created, and the recently-released All Yesterdays presented dinosaurs in unfamiliar scenes as a way to push artists to break from severely-constrained traditions. Dinosaurs were probably much more unusual than we have ever imagined.
Indeed, new discoveries this year extended the range of fluff and feathers among dinosaurs and raised the question of whether “enfluffledness” was an ancient, common dinosaur trait. Paleontologists confirmed that the ostrich-like Ornithomimus–long suspected to have plumage–sported different arrangements of feathers as it aged. New insight on the 30-foot-long carnivore Yutyrannus affirmed that even big tyrannosaurs were covered in dinofuzz. And while both Ornithomimus and Yutyrannus belonged to the feathery subset of the dinosaur family tree that includes birds, the discovery of fluff on a much more distantly related theropod–Sciurumimus–hints that feathers were a much older, more widespread dinosaur feature than previously expected. Paired with previous finds, Sciurumimus suggests that protofeathers either evolved multiple times in dinosaurian history, or that the simple structures are a common inheritance at the base of the dinosaur family tree that was later lost in some groups and modified in others.
While some traditionalists might prefer scaly dinosaurs over fuzzy ones, feathers and their antecedents are important clues that can help paleontologists explore other aspects of paleobiology. This year, for example, researchers reconstructed dark, iridescent plumage on Microraptor on the basis of fossil feathers, and, as display structures, feathery decorations will undoubtedly have a role to play in the ongoing debate about how sexual selection influenced dinosaur forms. Feathers can also be frustrating–a new look at the plumage of Anchiornis and Archaeopteryx will undoubtedly alter our expectations of how aerially capable these bird-like dinosaurs were and how they might have escaped predatory dinosaurs that dined on the prehistoric fowl. Such lines of inquiry are where the past and present meet–after all, birds are modern dinosaurs.
Feathers aren’t the only dinosaur body coverings we know about. Skin impressions, such as those found with the ankylosaur Tarchia, have also helped paleontologists discern what dinosaurs actually looked like. Pebbly patterns in Saurolophus skin can even be used to differentiate species, although paleontologists are still puzzled as to why hadrosaurs seem to be found with fossil skin traces more often than other varieties of dinosaur.
And, speaking of ornamentation, a damaged Pachycephalosaurus skull dome might provide evidence that these dinosaurs really did butt heads. How the adornments of such dinosaurs changed as they aged, though, is still a point of controversy. One of this year’s papers threw support to the idea that Torosaurus really is a distinct dinosaur, rather than a mature Triceratops, but that debate is far from over.
Other studies provided new insights into how some dinosaurs slept, the evolutionary pattern of dinosaur succession, what dinosaur diversity was like at the end of the Cretaceous, and how dinosaurs grew up, but, of course, how dinosaurs fed is a favorite place that lies at the intersection of science and imagination. A poster at the annual Society of Vertebrate Paleontology meeting deconstructed how Tyrannosaurus rex–suggested to have the most powerful bite of any terrestrial animal ever–tore the heads off of deceased Triceratops. The herbivorous Diplodocus, by contrast, munched soft plants and stripped branches of vegetation rather than gnawing on tree bark, and the tiny, omnivorous Fruitadens probably mixed insects with its Jurassic salads. Studying dinosaur leftovers also explained why paleontologists didn’t find more of the mysterious Deinocheirus, which thus far has been identified by only one incomplete fossil–the long-armed ornithomimosaur was eaten by a Tarbosaurus.
We also met a slew of new dinosaurs this year, including the many-horned Xenoceratops, the archaic coelurosaur Bicentenaria, the sail-backed Ichthyovenator, the stubby-armed Eoabelisaurus, and the early tyrannosaur Juratyrant. This is just a short list of species I wrote about–a few that add to the ever-increasing list.
To properly study dinosaurs and learn their secrets, though, we must protect them. One of the most important dinosaur stories this year wasn’t about science, but about theft. An illicit Tarbosaurus skeleton – pieced together from multiple specimens smuggled out of Mongolia–has brought wide attention to the fossil black market, as well as the poachers and commercial dealers who fuel it. The fate of this dinosaur remains to be resolved, but I’m hopeful that the dinosaur will be returned home and will set a precedent for more vigorously going after fossil thieves and their accomplices.
Out of all the 2012 dinosaur stories, though, I’m especially excited about Nyasasaurus. The creature’s skeleton is as yet too fragmentary to know whether it was true dinosaur or the closest relative to the Dinosauria as a whole, but, at approximately 243 million years old, this creature extends the range of dinosaurs back in time at least 10 million years. That’s another vast swath of time for paleontologists to examine as they search for where dinosaurs came from, and those discoveries will help us better understand the opening chapters in the dinosaurian saga. That’s the wonderful thing about paleontology–new discoveries open new questions, and those mysteries keep us going back into the rock record.
And with that, I must say goodbye to Dinosaur Tracking. On Tuesday I’m starting my new gig at National Geographic’s Phenomena. I’ve had a blast during my time here at Smithsonian, and I bid all my editors a fond farewell as I and my favorite dinosaurs head off to our new home.
Editor’s Note: Best wishes to Brian on his future travels and we all thank him for his hard work over the past 4 (!) years, writing every day about something new on dinosaurs. It’s not nearly as easy as he makes it look. – BW
December 13, 2012
Dinosaurs are much more than real monsters that fire our imaginations, but, let’s face it, part of their persistent appeal is that many were enormous prehistoric oddities. And it’s just that aspect of dinosaurian nature that is raising ire in a historically-rich California town and on an Australian golf course.
San Juan Capistrano, California is famous for the local cliff swallows and the historic Spanish architecture, but the town has recently been in the news because of an unwelcome dinosaur. According to the LA Times, a huge sauropod statue erected in the town’s petting zoo has drawn the ire of those who seek to retain some semblance of southern California’s past. Where kids and the zoo’s owner sees the dinosaur as a fanciful distraction, local historians argue that the dinosaur is totally out of place with the rest of the town’s decor. The dinosaur is staying put for now, but may yet be removed if the city decides that there’s just no place for a dinosaur in a place where Californian history and modern life already mix.
A different dinosaur is frustrating Australia’s professional golfers. The wealthy owner of the Palmer Coolum Resort has installed a 26 foot long, animatronic Tyrannosaurus rex in the middle of the course. Along with other recent installations, ESPN reports, the dinosaur is expected to adversely affect the games of Australian PGA Championship golfers set to play there. With the resort’s owner promising more dinosaurs on the way, the sports group has decided to move the tournament elsewhere after this year. Whether a sauropod looks out of place is one thing–having a T. rex get in the way of your shot is another.
Not everyone is so bothered by giant dinosaurs, though. A Best Western hotel in Colorado is taking on an entirely prehistoric theme, including fossil casts and dinosaur sculptures. In addition to attracting tourists, the hotel’s owner says he wants to draw attention to Colorado’s exceptional fossil sites, such as the nearby track site at Dinosaur Ridge. Dinosaur sculptures are frustrating eyesores to some and paleo-vacation essentials to others.
November 30, 2012
The dinosaurs I grew up with were both intensely exciting and incredibly dull. They were creatures unlike anything I had ever seen, but their drab, scaly flesh was always fit snugly to their bones with little embellishment. For decades, this has been the paradox of prehistoric restorations. Reconstructed skeletons are gloriously magnificent and introduce us to strange creatures that we never could imagined if we did not already know they existed. Yet the art of reviving these organisms has often been incredibly conservative. Dinosaurs, in particular, have often been “shrink-wrapped”–their skin tightly pulled around a minimalist layer of muscle distributed over the skeleton. This may be part of why dinosaur restorations look so weird. As John Conway, C.M. Kosemen, Darren Naish and Scott Harman argue in their new book All Yesterdays, no living lizard, fish, bird or mammal adheres to such a limited “skin on the bones” fashion. Dinosaurs were not only skeletally distinctive, but they undoubtedly looked stranger and behaved more bizarrely than we have ever imagined. The recently-published Dinosaur Art started to realize these possibilities, but All Yesterdays goes even further in melding science and speculation about dinosaur biology.
On a superficial level, All Yesterdays is a gorgeous collection of speculative artwork. Divided into two sections–the first featuring Mesozoic life in new or little-seen vignettes, and the second imagining how we would restore modern animals if we only had partial skeletons to work from–the book features some of the most wonderful paleoart I’ve ever seen. Scott Hartman’s crisp skeletal reconstructions form the framework from which Conway and Kosemen play with muscle, fat and flesh, and, following Naish’s introductory comments, Kosemen provides scientific commentary about how each illustration is not quite so outlandish as it seems. A curious Camptosaurus approaching an Allosaurus at rest is a reminder that, much like modern animals, prey and predators were not constantly grappling with each other, just as a snoozing rendition of the Tyrannosaurus “Stan” shows that even the scariest dinosaurs had to snooze. The gallery’s feathered dinosaurs are especially effective at demonstrating the fluffy weirdness of the Mesozoic. Conway’s peaceful scene of feather draped Therizinosaurus browsing in a tree grove is the best rendition of the giant herbivore I’ve ever seen, and his fluffy, snowbound Leaellynasaura are unabashedly adorable.
The second half of the book continues the same theme, but in reverse. How would artists draw a cat, an elephant or a baboon if we only had skeletons or bone fragments? And what would those scraps suggest about the biology of long-lost animals? If there are paleontologists in the future, and they have no other source of information about our world, how will they restore the animals alive today? They might have no knowledge of the fur, fat, feathers and other structures that flesh out modern species, creating demonic visions of reptilian cats, eel-like whales and vampire hummingbirds.
Working in concert, the two sections will give casual readers and paleoartists a jolt. While some might gripe about Todd Marshall adding too many spikes and dewlaps to his dinosaurs, or Luis Rey envisioning deinonychosaurs at play, the fact of the matter is that dinosaurs probably had an array of soft tissue structures that made them look far stranger than the toned-down restorations we’re used to. As All Yesterdays presents in various scenes, maybe sauropods liked to play in the mud, perhaps hadrosaurs were chubbier than we ever imagined and, as depicted in one nightmare-inducing panel, Stegosaurus could have had monstrous genitals. None of these scenarios are supported by direct evidence, but they are all within the realm of possibility.
More than a gallery of speculative art, All Yesterdays is an essential, inspirational guide to any aspiring paleoartist. Those who restore prehistoric life are limited by the evidence at hand, this is true, but “more conservative” does not mean “more accurate.” Using comparisons with modern animals, artists have far more leeway than they have ever exercised in imagining what prehistoric life was like. We’ve seen enough Deinonychus packs tearing apart Tenontosaurus, and far too many malnourished dinosaurs. We need more fat, feathers, accessory adornments and scenes from quieter moments in dinosaur lives that do not involve blood and spilled viscera. Professional paleoartists are beginning to embrace these ideas–Jason Brougham’s recent restoration of Microraptor is an appropriately fluffy, bird-like animal rather than the flying monster Naish and collaborators decry–but All Yesterdays is a concentrated dose of prehistoric possibilities that are being artistically explored.
Some of the book’s restorations may turn out to look quite silly. As lovely as Conway’s rendition is, I still don’t buy the “bison-back” idea for high-spined dinosaurs such as Ouranosaurus. Then again, depending on what we discover in the future, some of the illustrations might seem quite prescient. The important thing is that All Yesterdays demonstrates how to push the boundaries of what we imagine while still drawing on scientific evidence. The book is a rare treat in that each section explicitly lays the inspiration for each speculative vision, providing references for those who want to dig deeper.
If anything, All Yesterdays shows that we should not be afraid of imagination in science. Even though we know far more about dinosaur biology and anatomy than ever before, there are still substantial gaps in our understanding. In these places, where bones might not have much to tell us, science meets speculation. The result is not anything-goes garishness, but an exploration of possibilities. Somewhere within that murky range of alternatives, we may start to approach what dinosaurs were truly like.
You can purchase All Yesterdays in any of its various formats here.
November 29, 2012
When I was first becoming acquainted with dinosaurs in the mid 1980s, “theropod” was synonymous with “carnivorous dinosaur.” Large or small, from Tyrannosaurus to Compsognathus, every theropod I knew of sustained itself on the flesh of other organisms. But it was just about that time that new discoveries and analyses revealed that many theropod dinosaurs were omnivores, or even herbivores. The ostrich-like ornithomimosaurs, beaked oviraptorosaurs and utterly bizarre therizinosaurs, in particular, embodied a switch from an ancestral meat-filled diet to one more reliant of fruit and foliage. Not only that, but these herbivorous theropods grew almost as large as the biggest carnivores–the ornithomimosaur Deinocheirus, the ovriraptorosaur Gigantoraptor and Therizinosaurus were all enormous Cretaceous dinosaurs. But why did these plant-chomping dinosaurs become giants?
In the latest of a spate of papers considering herbivorous theropods, paleontologists Lindsay Zanno and Peter Makovicky paired evolutionary trees with mass estimates derived from femora lengths and a bit of number crunching to see if there was any distinct evolutionary pattern that might explain why Deinocheirus and similar herbivorous theropods grew to such large sizes. Were these Late Cretaceous dinosaurs just the culmination of an evolutionary trend towards ever-larger body size–called Cope’s Rule–or was something else at work?
Zanno and Makovicky didn’t find any sign of directional selection for larger body size. Even though the earliest representatives of the ornithomimosaurs, oviraptorosaurs and therizinosaurs in Asia were much smaller than their Late Cretaceous relatives, the paleontologists point out that this signal has probably been biased by preservation. The 125-million-year-old deposits that contain small members of these groups seem to be skewed towards “mid-sized vertebrates,” the authors point out, and don’t seem to preserve larger dinosaurs that might belong to the same lineages. Indeed, therizinosaurs of about the same age from North America, such as Falcarius, were larger than species in Asia, meaning that herbivorous dinosaurs might have occupied a range of body sizes and evolved larger body sizes at multiple intervals. There was no simple, straight-line trend of bigger and bigger bodies through time.
Nor did a herbivorous lifestyle alone seem to account for gigantism among these dinosaurs. Even though big herbivores gain particular benefits from their size in terms of breaking down tough, low-quality foods more efficiently, Zanno and Makovicky doubt that this relationship drove the evolution of increased body size in the dinosaurs. Instead, they favor “passive processes” that might be tied to ecology and whether these dinosaurs were omnivores more than herbivores. And, as the paleontologists stress, the pattern relies on how complete we think the dinosaur record is. Some ecosystems might be preferentially preserving larger or smaller dinosaurs, which has the potential to skew the big picture. While Zanno and Makovicky ruled out some possibilities, we still don’t really know what accounts for the multiple herbivorous theropod growth spurts.
Post-Script: After four years working with Smithsonian magazine’s wonderful crew, and over 1,000 posts about various aspects of dinosauriana, it’s time for me to move on. I’ll be leaving Dinosaur Tracking next month. Don’t fret, I’ll still be digging into dinosaur science, but I’ll be at a new blog elsewhere on the web (stay tuned for details). I am deeply indebted to my editors Brian Wolly, Sarah Zielinski and, of course, Laura Helmuth (now doing a great job at Slate), as well as the rest of the Smithsonian staff for inviting me to come here and geek out about dinosaurs every day. And many thanks to all of you–the readers and commenters who have helped make this blog a success. You have all made blogging for Dinosaur Tracking an absolute pleasure.
Zanno, L., Makovicky, P. 2012. No evidence for directional evolution of body mass in herbivorous theropod dinosaurs. Proceedings of the Royal Society B. 280. doi: 10.1098/rspb.2012.2526
November 16, 2012
Many dinosaurs have gained fame thanks to their gargantuan size. A creature in the form of a dipldodocid or tyrannosaur would be wonderful at any scale, but the fact that Apatosaurus was an 80-foot-long fern-sucker and Tyrannosaurus was a 40-foot carnivore make their skeletal frames all the more spectacular. Even as an adult, long after my first encounter with their bones at the American Museum of Natural History in New York City, I still feel tiny when I look up at what’s left of the great dinosaurs.
But not all non-avian dinosaurs were gigantic. There were 100-foot giants, like the sauropod Argentinosaurus, but there were also pigeon-sized theropods such as the strikingly-colored Anchiornis. Indeed, a significant part of how we know dinosaurs really ruled the earth is because they occupied such a wide range of body sizes–from the breathtakingly large to the diminutive. And, earlier this month, Field Museum of Natural History paleontologist Peter Makovicky and colleagues added a previously unknown tiny dinosaur to the ever-growing roster of Mesozoic species.
Named Alnashetri cerropoliciensis, the small dinosaur is mostly a mystery. All that we know of it, Makovicky and coauthors report, are a set of articulated hindlimbs from a single animal found in the roughly 95-million-year-old rock of La Buitrera, Argentina. (The dinosaur’s genus name, the paper says, means “slender thighs” in a dialect of the Tehuelchan language.) Yet those appendages contain enough clues about the dinosaur’s identity that the researchers were able to figure out that the specimen represented a new species of alvarezsaur–one of the small, possibly ant-eating dinosaurs recognizable by their short, stout arms and long skulls set with tiny teeth. While the paleontologists acknowledge that their Alnashetri specimen might be a juvenile, Makovicky and collaborators estimate that the dinosaur was comparable to its relative Shuvuuia in size–about two feet long.
How Alnashetri resembled other alvarezsaurs, and where it departed in form, will have to wait for more complete specimens. Further research is also needed to narrow down when this dinosaur lived, but for the moment, Alnashetri appears to be the oldest alvarezsaur found in South America. If only we knew more of this dinosaur! As Makovicky and coauthors conclude, “continued fieldwork and future discoveries hopefully will provide more information on the anatomy of Alnashetri and allow a more definitive evaluation of its affinities and its significance for understanding biogeography and evolutionary trends such as body size evolution within alvarezsaurids.” At least the enigma has a name.
Makovicky, P., Apesteguía, S., Gianechini, F. 2012. A new coelurosaurian theropod from the La Buitrera fossil locality of Rio Negro, Argentina. Fieldiana Life and Earth Sciences, 5: 90-98