May 9, 2012
It sounds like perfect journalist bait: Earlier this week, a new Current Biology paper proposed that the accumulated output of dinosaur farts could have changed the global climate. You could hardly ask for a better story. Dinosaurs are ever-popular media darlings, and the science of sauropod farts is just silly enough to grab the public’s attention. Too bad sources like FOX News, Gawker and the Daily Mail issued some rather noxious stories about the research.
The paper itself, written by researchers David Wilkinson, Euan Nisbet and Graeme Ruxton, is an exercise in short but serious speculation. For a long time, the digestive biology of sauropods has confounded paleontologists. Sauropods had small teeth good for gripping, nipping and plucking plants, but not for chewing or otherwise mashing up their food. How they broke down the masses of plant food they must have required is a mystery. For a time, swallowed stones called gastroliths were thought to be the answer, but recent reviews of the evidence have failed to turn up any indication that stones ground up food in sauropods’ guts. Instead, some paleontologists have gravitated toward the idea that sauropods had vast communities of microscopic organisms in their stomachs that broke down the incoming plants. This microorganism-assisted fermentation could have produced methane, and as Wilkinson and co-authors point out, sauropod farts would have been the end result.
Since emissions from cows and other livestock contribute greenhouse gases to our warming atmosphere, Wilkinson and collaborators wondered if sauropods might have had a similar effect on the Mesozoic world. To find out, they paired estimates of sauropod population size derived from the fossil record of the roughly 150-million-year-old Morrison Formation—the geological slice in which Apatosaurus, Diplodocus, Barosaurus and other Jurassic giants are found—with an estimate of how much methane each dinosaur would produce based on observations of modern rabbit and guinea pig emissions. Assuming that ten Apatosaurus-size sauropods lived per square kilometer, and that half the world’s land area was inhabited by dinosaurs, Wilkinson and colleagues found that the giant, long-necked dinosaurs would have produced 520 million metric tons of methane annually. In their estimation, this is comparable to the amount of methane that we’re currently pumping into the atmosphere each year. The researchers conclude that so much dinosaur flatulence—in addition to greenhouse gases from fires and other sources—might have created and sustained the relatively warm world of the dinosaurs.
But we don’t know for sure. The new research relies on a stack of assumptions and is, at best, a rough model. We don’t know what the gut flora of sauropods was like; therefore, we don’t know whether they farted at all. And small, mammalian herbivores such as rabbits and guinea pigs are unlikely to be the best models for sauropod emissions. Living dinosaurs and their cousins aren’t much help here. Modern avian dinosaurs don’t fart, and I haven’t seen any research on whether crocodylians—the closest living cousins of dinosaurs as a whole—produce methane-rich eruptions. (If you know about croc fart research, please chime in.)
It’s not unreasonable to wonder about dinosaur digestive products. Paleontologist Tony Fiorillo speculated about hadrosaur gas at a 2010 American Geophysical Union meeting. Perhaps fortunately, our ability to investigate dinosaur farts is severely limited. Furthermore, paleo-blogger Jon Tennant names a number of other problems with the back-of-the-envelope calculations at the heart of the paper—including the estimates of sauropod abundance worldwide—and rightly concludes that the paper is a “crude analysis.”
The media coverage has been even cruder. In the past month we’ve had vapid reports of aquatic dinosaurs and alien dinosaurs, but at least three news sources decided to up the ante with additional bad reporting. Fox News led off with “Dinosaurs may have farted themselves to extinction, according to a new study from British scientists.” Wrong right out of the gate. Wilkinson and co-authors didn’t say a thing about dinosaur extinction in their paper. Not to mention that the idea doesn’t make any sense. Titanic sauropods were around for about 130 million years. If their gases were so deadly, why did it take so long for the world to be overwhelmed? The Fox News gloss isn’t even a misrepresentation of what the researcher said. The story’s headline and lead are outright fabrications. And the same fiction was repeated on the network’s late-night roundtable of chattering commentators, Red Eye.
Gawker simply recycled Fox’s bad air. “A new study from British scientists published in Current Biology suggests the dinosaur infraorder known as sauropods may have actively contributed to its own extinction through excessive flatulence,” wrote site contributor Neetzan Zimmerman, who linked backed to the Fox News item. News aggregation and snarky commentary are popular right now, and in cases like this, lazy and sensationalist reporting can rapidly be echoed across the web. Although I’m not going to give the typically awful Daily Mail credit for independently misconstruing the paper’s results.
The Daily Beast’s Daniel Stone and PZ Myers of Pharyngula tore into the media coverage earlier this week. There’s sadly no shortage of facepalm-inducing reporting, but it’s even worse when news sources are so enamored with a punchline that they simply make up conclusions. Not that I expect Fox News, the Daily Mail, or Gawker to stop blowing hot air whenever the opportunity arises.
Wilkinson, D., Nisbet, E., & Ruxton, G. (2012). Could methane produced by sauropod dinosaurs have helped drive Mesozoic climate warmth? Current Biology, 22 (9) DOI: 10.1016/j.cub.2012.03.042
August 5, 2010
During the past week, people all over the Internet have driven themselves into a tizzy over the new study by John Scanella and Jack Horner in which the paleontologists hypothesized that the dinosaur known as Torosaurus was really the adult stage of the more familiar Triceratops. “Triceratops Never Existed” said the headline from Gizmodo (as did similar ones from CBS News, the National Post, the Baltimore Sun, the San Francisco Chronicle, and Newsoxy), while another one went as far as to ask “Triceratops a Hoax?” In comment sections and on Twitter people have been, well, all a-twitter about the idea that one of their favorite dinosaurs might be taken away—some folks likened the situation to the “demotion” of Pluto via t-shirt designs and others set up Facebook campaigns to “Save the Triceratops.”
All of this angst is unnecessary. As Scanella and Horner pointed out in their paper, and as multiple summaries of the study have stated, Triceratops (described in 1889) was named before Torosaurus (described in 1891). According to the rules by which scientists name organisms, this gives Triceratops priority, so the name “Triceratops” isn’t going anywhere. (TIME got it right, Love in the Time of Chasmosaurs tried to set people straight, and Geekosystem deserves some credit for amending their original post.) What is significant about the new study is that it may change our perception of what an adult Triceratops looked like, but the young-adult dinosaur we have traditionally called Triceratops is just as real as tadpoles, caterpillars, or teenage humans—they are all growth stages within a species. Given the number of Triceratops remains that have been recovered from western North America, there has never been any doubt that it was a real animal, though I am sure that many people are much happier calling it Triceratops rather than Torosaurus.
June 25, 2010
Mammals have long been characterized as the underdogs of the Mesozoic world. They diversified in habitats ecologically dominated by dinosaurs, but, even though most were small, they did not simply cower in their burrows until the non-avian dinosaurs were wiped out 65 million years ago. In fact, Mesozoic mammals were more varied in anatomy and habits than is often appreciated, and, as has just been reported in Palaeontology, some small mammals gnawed the bones of the giant archosaurs.
As described by paleontologists Nicholas Longrich and Michael Ryan, a number of fossil bones from the Cretaceous rock of Alberta, Canada were damaged by bites which could only have been made by mammals. A dinosaur rib fragment, a piece of dinosaur limb bone, a partial lower jaw from the marsupial mammal Eodelphis and a femur from a reptile called a champosaur bear bite marks made by an animal with closely-spaced, paired teeth. This bite pattern matches the tooth placement of an extinct variety of mammal called multituberculates—these mammals had long incisor teeth at the front of their jaw separated from the other teeth by a gap, thus explaining why the only toothmarks on the bones were made by incisors. While other mammals could potentially have been the culprit, the anatomy of the multituberculates make them the best fit.
The multicuberculate-made toothmarks are, at present, the oldest known fossil traces of mammal toothmarks. More than that, the authors suggest that some multituberculates used their incisors to gnaw on hard, resistant food items, meaning that they were perhaps more versatile in their diets than had previously been presumed. From the traces on the bones it appears that these small mammals scavenged dead dinosaurs and other creatures for food (leaving behind the relatively shallow tooth marks on some of the specimens) and sometimes bit into the bone itself, perhaps to obtain minerals like calcium (as seen by the deeper bite marks). Now that these traces have been recognized, perhaps other paleontologists will see similar marks in bones they collect, potentially helping us better understand the lives of the mammals that lived alongside the dinosaurs.
LONGRICH, N., & RYAN, M. (2010). Mammalian tooth marks on the bones of dinosaurs and other Late Cretaceous vertebrates Palaeontology DOI: 10.1111/j.1475-4983.2010.00957.x
June 3, 2010
Last month a group of nine students from Montana State University, Dawson Community College and Rocky Mountain College left for China to study dinosaur eggs, and they have been chronicling their experiences on the new blog MSU China Paleontology Expedition. About two weeks into their six-week stay, most of the posts so far cover “culture shock” (both on the part of the Montana students and the Chinese citizens they encounter), though some of the more recent posts have begun to share the scientific work being undertaken by the team. Among things the students have been studying: the sediment encasing some of the eggs to figure out what kind of environment they were preserved in, and I look forward to reading more updates from the students during the rest of their stay in China.
May 10, 2010
Almost everyone is familiar with the ongoing debate surrounding the extinction of the non-avian dinosaurs 65 million years ago, but the discussion over where dinosaurs came from in the first place is often overlooked. Hypotheses of dinosaur origins have been just as controversial as those of triggers for the end-Cretaceous mass extinction, but during the past few decades numerous new discoveries have helped scientists better understand the early evolution of dinosaurs. What we presently understand about the evolution of these famous vertebrates is presented in a new review by paleontologists Stephen Brusatte, Sterling Nesbitt, Randall Irmis, Richard Butler, Michael Benton, and Mark Norell in Earth Science Reviews.
As pointed out by the team of scientists, a good place to start the story of the dinosaurs is with the mass extinction that occurred about 251 million years ago at the end of the Permian. This event, the worst mass extinction in the history of life on Earth, drastically cut down the diversity of the dominant terrestrial vertebrates (such as synapsids, a group containing our ancestors and creatures more closely related to us than to reptiles) and allowed the surviving groups to radiate in a changed landscape. Among the groups to evolve in the wake of the disaster were the first archosaurs, and these were the earliest representatives of the group to which crocodiles, pterosaurs, dinosaurs and numerous other lineages of reptiles belonged.
The Triassic became the heyday of the archosaurus—numerous groups evolved and radiated into a variety of forms such as the gavial-like phytosaurs and the terrifying rauisuchians—but dinosaurs were relative latecomers. Recent discoveries have identified creatures such as Asilisaurus as among their closest relatives, hence providing paleontologists with clues as to what the ancestors of the first dinosaurs might have been like, but it was not until about 230 million years ago in the Late Triassic that the first true dinosaurs appeared. They were relatively small animals that lived in a warm, seasonal world inhabited by many other archosaurs, but another mass extinction at the end of the Triassic about 200 million years ago (possibly triggered by intense volcanic activity) cleared away many of the archosaur lineages. Dinosaurs, however, persisted through the event, and the beginning of the Jurassic marked the beginning of their rise to ecological dominance.
Dinosaurs had split into two main groups relatively early in their evolution—the saurischians (containing theropods and the long-necked sauropods) and the ornithischians (the diverse group of dinosaurs that contains hadrosaurs, ceratopsians, ankylosaurs etc.)—but during the Jurassic the different lineages within these groups evolved into a dazzling array of creatures. New types of large predatory theropods like Dilophosaurus set out after sauropodomorphs such as Seitaad and some of the earliest true sauropods, and while the early history of ornithischian dinosaurs is less well-known, the transition from the Triassic into the Jurassic unambiguously shows that this group, too, was undergoing its own radiation. Indeed, not only were there more dinosaurs around during the Early Jurassic, but they were becoming increasing disparate from each other, or, in other words, becoming adapted into a variety of shapes and sizes not seen before.
The paper itself presents more important details of early dinosaur evolution that can be mentioned here, but suffice it to say that the information paleontologists have discovered since the 1980s has greatly revised old notions of the pattern of dinosaur origins. Contrary to what was believed during the mid-2oth century, the seeming evolutionary ascent of the dinosaurs was not the result of their inherent superiority over other groups of organisms (a notion that stemmed from the notion that evolution is progressive, pushing creatures towards greater levels of absolute perfection). Instead the emergence of dinosaurs was contingent on chance events that could not have been been predicted—chance and evolutionary history played important roles in the early evolution of dinosaurs. Had the mass extinction at the end of the Permian never occurred, for example, there may never have been the dramatic radiation of archosaurs seen during the Triassic, and this would have drastically changed the history of life on Earth.
Viewed as a whole, the story of dinosaurs is a tale of how life on Earth reacts to mass extinctions. Dinosaurs rose to prominence because of mass extinctions, yet most of them (the exception being their bird descendants) succumbed to another ecological catastrophe 65 million years ago. As the authors themselves conclude:
… there was nothing predestined or superior about dinosaurs when they first arose, and without the contingency of various earth-history events during the early Mesozoic, the Age of Dinosaurs might have never happened.
Brusatte, S., Nesbitt, S., Irmis, R., Butler, R., Benton, M., & Norell, M. (2010). The origin and early radiation of dinosaurs Earth-Science Reviews DOI: 10.1016/j.earscirev.2010.04.001