Courtesy of Brian Switek

Dinosaur enthusiast Brian Switek surveys Utah's landscape during a road trip — and surveys the state of dinosaur lore in "My Beloved Brontosaurus."

When it comes to dinosaurs and other prehistoric monsters, even the experts can get things wrong — as dino-fanatic Brian Switek explains in his tour guide to the paleontological frontier.

The righting of wrongness begins with the title of Switek's book: "My Beloved Brontosaurus: On the Road With Old Bones, New Science and Our Favorite Dinosaurs." As most 9-year-olds could probably tell you, there's officially no such thing as a Brontosaurus. That name for the quintessential long-tailed, long-necked sauropod went out of fashion when scientists figured out that the Jurassic giant had already been dubbed Apatosaurus.

Nevertheless, the brontosaur serves as a totem for Switek, a prolific science writer whose work has appeared in Wired, Smithsonian, Slate, Scientific American and now most frequently on National Geographic's Phenomena blog network (as Laelaps). His earlier book, "Written in Stone," laid out the broad sweep of stories told by the fossil record — and in "My Beloved Brontosaurus," he focuses in on the what, where and when of the dinosaurs' heyday in the Mesozoic Era.

As you page through the book, you'll learn that not all dinosaurs have gone extinct. (Birds are dinosaurs.) You'll find out that the dinosaurs didn't start out as the rulers of the reptiles. (Crocodilians came first.) You'll delve into the back-and-forth debates that have occupied paleontologists for decades. (Was T. rex a hunter or a scavenger? Almost certainly both.) And you'll also get some great tips for future road trips in the American West.

Misconceptions and marvels
Switek talked about dinosaurs and tour directions during an interview last week. Here's an edited version of the Q&A that will whet your appetite for "My Beloved Brontosaurus":

Q: So many myths about dinosaurs are exploded in your book, but is there one big misconception that you want to set people straight about?

A: There’s one misconception that has a flip side to it, and that’s that dinosaurs are totally extinct. Birds are living dinosaurs. We figured that out about 20 years ago. So whenever we talk about the age of dinosaurs millions of years ago, and how all the dinosaurs are gone, that’s demonstrably not true. At least one lineage is still with us today.

The flip side of that is that dinosaurs became dominant as soon as they appeared — that the dawn of the dinosaurs sparked an immediate rise to ascendancy. The fact is that dinosaurs started out relatively small. They were relatively marginal. They really weren’t all that important until the extinction at the end of the Triassic period, about 200 million years ago, wiped away all the weird crocodile relatives that were the dominant land animals at the time. So the dinosaurian reign was made possible by, and then winnowed back by, extinction. It’s these wonderful extinction bookends that explain not only their origin, but their ultimate destination, bringing us to the birds that live today.

Q: Another issue is the appeal of dinosaurs: For some kids, dino-mania is almost a rite of passage. I love the idea that the book jacket for “My Beloved Brontosaurus” is also a fold-out dinosaur poster — what dinosaur fan wouldn’t love that? What is it about dinosaurs that makes them so appealing, particularly to kids?

A: I think they’re appealing because they demand answers of us. People have been wondering about dinosaurs, pondering what they were and what they were like, even before there was a name for them. I don’t just mean European naturalists. I mean Native Americans, people in ancient Greece and Rome, people in ancient China and India. People in all those cultures found dinosaur bones. They knew that these were the remains of once-living animals, and they created stories of monsters and heroes, myths and legends about creatures from distant times. So we were wondering about the dinosaurs before we even knew what they were.

That continues now, because there’s nothing quite like the dinosaurs. Yes, birds are living dinosaurs – but there’s so much more. There’s nothing like Apatosaurus, or Triceratops, or Tyrannosaurus rex around right now. When you look at their bones, questions immediately come to mind: What did they look like? What did they sound like? How quickly did they move? What did their environment look like? To me, it’s impossible to hear the dinosaur story without wondering about these questions.

Answering these questions puts our own existence in context. You can say all this happened 66 million years ago – but wait a second: What was America like back then? How did it all change? That brings up some very powerful truths about extinction, evolution and survival.  It’s these clues from our own distant past and our planet’s distant past that act as milestones by which we can understand our own existence.

J. Brougham / AMNH file

Experts say Tyrannosaurus rex may have had a downy layer of feathers, and probably had a coloration that was more varied than the stereotypical green.

Q: Another way that the book could be read is as a travelogue. It’s almost structured as a series of road trips that you’ve taken to explore all these fantastic fossils. And in fact, that’s what you’re doing along with your book tour. If there’s one dream trip that dinosaur fanatics should take, where would you tell them to go?

A: This is sort of a plug for my home state of Utah: There’s a byway system called the Dinosaur Diamond that runs through a good part of the state and includes the Dinosaur National Monument, where 150 million-year-old fossils are preserved in place; and the Cleveland-Lloyd Dinosaur Quarry, a place where over 46 individual allosaurs and other dinosaurs have been found. You can head up to Salt Lake City, where the Natural History Museum of Utah opened this last year. As you drive along those highways, there are various dinosaur trackways, lots of attractions, lots of dinosaur celebrities. So if anyone’s looking for a weeklong trip in the American West, that’s the best pre-planned tour there is for a dino fan.

Q: in terms of the frontiers for dinosaur research, there’s been talk about Jack Horner’s "Chickenosaurus" project, and there are always new perspectives on how dinosaurs lived and died. What do you see as the next big thing for dinosaur research?

A: Researchers are finding ways to draw out clues about how dinosaurs actually lived, through new technologies that can be applied to a variety of animals. So we’re looking at the development of better CT scanning technology. Improved CT technology is helping paleontologists get down to a degree of resolution they’ve never had before — and they’re finding clues about bone structure to a degree that was just not possible before.

What’s really exciting to me is the study of dinosaur color. It’s a field that’s moving forward by comparing fossil feathers to modern ones. Paleontologists are starting to reconstruct what colors the dinosaurs actually were. They might be able to identify the evolutionary advantages of colors, degrees of coloration, and maybe some aspects of sexual dimorphism. Everything we’re learning about dinosaur biology is filling in the picture of how they lived in a much more meaningful way.

Q: You mentioned that dinosaurs are appealing to us in part because they tell us how extinction works, and how our own distant past might have unfolded. That suggests that the study of dinosaurs can hold lessons for the 21st century. How can the dinosaur experience best be applied to our own human experience?

A: Dinosaurs shaped our evolution. People often say that the rise of mammals was made possible by the disappearance of all those non-avian dinosaurs. That's true, but it's not just that. Mammals lived alongside the dinosaurs — things like Stegosaurus and Allosaurus and Tyrannosaurus. By keeping our furry little ancestors in the shadows, the dinosaurs set the stage for the later evolution of primates.

Yes, those dinosaurs disappeared. But beyond that, we know that we’re changing the global climate in drastic ways. We know we’re distributing invasive species around the world. By looking back at the fossil record, and seeing how dinosaurs reacted to drastic changes, we can begin to outline how organisms today and in the future are going to react to the same sorts of changes. Dinosaurs might hold clues about our future. The past isn't just a static monument to what once was. The fossil record also carries lessons about what will be. 

For much, much more about dinosaur wrongness and rightness, check out the latest 'Virtually Speaking Science' podcast with Switek and University of Maryland paleontologist Tom Holtz. You can download a variety of VSS podcasts from BlogTalkRadio or iTunes.

More 'Virtually Speaking Science' podcasts:

• George Djorgovski on the Internet and education
• Doug Griffith and Taber MacCallum on moon and Mars trips
• Sean Carroll and Matt Strassler on physics' X Files
• Ig Nobel's Marc Abrahams on weird science in 2012
• Paul Doherty on Curiosity and the year in science
• Shawn Lawrence Otto on climate change and the 2012 election
• Sean Carroll on what lies beyond the Higgs boson
• Alan Stern on the Uwingu mystery space venture
• George Djorgovski on the future of immersive virtual reality
• JPL's Dave Beaty previews Curiosity's mission on Mars
• SETI Institute's Seth Shostak about aliens and UFOs
• Paul Doherty on solar eclipses and the transit of Venus
• Veronica Ann Zabala-Aliberto on spaceflight and Yuri's Night
• JPL's Dave Beaty on the search for life on Mars
• Shawn Lawrence Otto on science and politics
• Ig Nobel impresario Marc Abrahams on silly science in 2011
• Rocket scientist Robert Zubrin on Mars exploration
• Propulsion expert Marc Millis on interstellar spaceflight
• Sean Carroll on the puzzles facing physicists
• Rand Simberg on the private-enterprise vision for spaceflight
• Martin Hoffert on the future of energy policy
• George Djorgovski on science in virtual worlds
• Alan Stern on suborbital research and NASA's mission to Pluto
• Col. 'Coyote' Smith on the outlook for space solar power
• Tim Pickens on rocket ventures and the Google Lunar X Prize

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

This story was originally published on Wed May 1, 2013 4:50 PM EDT

Carl Buell

In this artist's conception, the carnivorous lizard Palaeosaniwa stalks a pair of hatchling Edmontosaurus dinosaurs as the snake Cerberophis looks on from above, and the lizard Obamadon watches from below. Meanwhile, in the background, a Tyrannosaurus rex encounters a Triceratops troop while an asteroid streaks down to Earth.

The mass extinction that killed off the dinosaurs 65 million years ago also did in lots of lizards — including a newly identified creature that's been named Obamadon gracilis in honor of President Barack Obama.

Obama already has a type of fish (Ethiostoma obama) and lichen (Caloplaca obamae) named after him, and now the recently re-elected leader of the free world can add a foot-long, slender-toothed casualty of the Cretaceous-Tertiary extinction to the list.

Yale paleontologist Nicholas Longrich, the lead author of a paper announcing the find in the Proceedings of the National Academy of Sciences, told me that the name arose from a conversation he had with a friend in late 2008, when folks were wondering how Obama's election would change the political scene.

"I said, yeah, we should name a dinosaur after him," Longrich said. "It was sort of a smart-ass comment."

But the idea stuck. After all, this is the guy who named a different fossil "Mojoceratops."

"It was catchy, and it seemed like a fun thing to do," he said.

There's a serious point behind the paper, of course: Longrich and his colleagues analyzed at fossils representing 30 different types of snakes and lizards, previously collected from locales in western North America ranging from New Mexico to Alberta. Nine of the species, including Obamadon, were previously unrecognized.

"Lizards and snakes rivaled the dinosaurs in terms of diversity, making it just as much an 'Age of Lizards' as an 'Age of Dinosaurs,'" Longrich said in a Yale news release.

Previous studies had suggested that some snake and lizard species went extinct, along with the dinosaurs and many types of mammals, birds, insects and plants. The extinction was presumably due to a catastrophic asteroid strike on Mexico's Yucatan Peninsula.

The new survey suggests that snakes and lizards were hit much harder than previously thought. Longrich and his colleagues estimate that up to 83 percent of all snake and lizard species were killed off. The bigger the creature, the more likely it was to become extinct: The researchers concluded that no species weighing more than a pound survived.

Obamadon was part of a group of creatures known as polyglyphanodonts, which accounted for up to 40 percent of the lizards living in North America before the extinction. Obama's namesake was identified on the basis of jaw fossils from Montana's Hell Creek Formation, with "tall, slender teeth with large central cusps separated from small accessory cusps by lingual grooves."

The lizard was less than a foot long and probably caught insects in its teeth, Longrich said.

The discovery of Obamadon just goes to show how new discoveries can come from old specimens — including fossils that were collected years ago, by paleontologists who were focusing dinosaurs or early mammals rather than snakes or lizards. "There hasn't been a heck of a lot of interest in these specimens," Longrich said. "Here we have all this data that's there, waiting to be studied."

Two of the newly recognized fossil species don't yet have scientific names, but when it comes time for the naming, rest assured that Longrich won't come up with anything too wild and crazy.

"We decided not to do the Hitlerosaurus," he said.

More about celebrity species:

• Lady Gaga immortalized in ferns
• Parasite named after reggae star Bob Marley
• 'Bootylicious' fly named after Beyonce
• 'Venus Rat-Trap' named after TV naturalist
• 'The Hoff' loves his celebrity crabs
• What's in a scientific name? (Scroll down)

In addition to Longrich, the authors of the paper in the Proceedings of the National Academy of Sciences, "Mass Extinction of Lizards and Snakes at the Cretaceous-Paleogene Boundary," include Bhart-Anjan S. Bhullar and Jacques A. Gauthier. Longrich says the Cretaceous-Paleogene boundary is a more recent term that applies to the mass extinction also known as the Cretaceous-Tertiary boundary.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Paleontologists are still debating whether dinosaurs met their doom quickly or gradually, due to a catastrophic cosmic impact — but thanks to a crazy YouTube video, you can watch the "domino-saurs" die out in a minute and a half.

The way it's portrayed by FlippyCat (a.k.a. Randy Granger of Winnipeg, Canada), a little gray block of dominoes from outer space sets off a chain reaction that spreads across the globe — killing off cute little baby dinosaurs, smashing a big old sauropod to bits and tumbling the bones of a dinosaur skeleton.

It always takes more time to build things up than to knock them down, and that was the case for the demise of the domino-saurs. "This took 38.5 hours of setup time, over about two weeks," FlippyCat wrote. Once you see the behind-the-scenes footage that follows the initial sequence, you'll understand why that is. And you'll probably continue clicking to see some of FlippyCat's other projects, including a domino interpretation of Psy's "Gangnam Style" viral video.

In reality, the death of the dinosaurs took much longer than a minute and a half, and some paleontologists suspect the biggest dinosaurs were already on the way out when that big asteroid hit Mexico's Yucatan Peninsula 65 million years ago.

More about the dinosaurs' demise:

• 'Rock-solid' case: Asteroid killed the dinosaurs
• Theory about dino-killing firestorm questioned
• Some dinosaurs survived asteroid impact
• Were the dinosaurs done in by gas?

Tip o' the Log to Brian Switek at Dinosaur Tracking.

Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

U.S. Attorney's Office

This photo, attached as an exhibit to the complaint filed by federal attorneys, shows the tyrannosaur skeleton that has stirred up an international legal dispute.

Federal attorneys today filed a civil lawsuit that seeks to wrest a tyrannosaur skeleton valued at more than $1 million away from its sellers and return it to the Mongolian government.

The skeleton was sold at a New York auction last month for $1.05 million to an unidentified buyer, even though a federal district judge in Texas issued a restraining order to hold up the sale. The auction house behind the offering, Texas-based Heritage Auctions, made the sale contingent on the outcome of Mongolia's court challenge — and since then, the skeleton has been held in legal limbo.

Earlier this month, a panel of paleontologists declared that the skeleton represented a Tyrannosaurus bataar, also known as a Tarbosaurus bataar, which was probably smuggled out of Mongolia sometime in the past 15 years or so. Today's complaint, filed by the U.S. attorney for Manhattan in New York federal district court, follows up on that determination and lays out the authorities' version of a tangled tyrannosaur tale.

"The skeletal remains of this dinosaur are of tremendous cultural and historical significance to the people of Mongolia, and provide a connection to the country's prehistoric past," Manhattan U.S. Attorney Preet Bharara said in a statement. "When the skeleton was allegedly looted, a piece of the country's natural history was stolen with it, and we look forward to returning it to its rightful place."

Mongolia has had laws on the books forbidding the export of dinosaur fossils since 1924. The complaint says the nearly complete skeleton was brought into the United States illegally, and thus should be forfeited by the sellers and returned to Mongolia.

James Hayes, a special agent-in-charge for the U.S. Immigration and Customs Enforcement's Homeland Security Investigations, said the complaint alleges that "criminal smugglers misrepresented this fossil to customs officials."

When the skeleton was imported into the United States from Britain in 2010, the country of origin was listed as Britain — even though, according to the paleontologists, nearly complete tyrannosaur skeletons of this type have been found only in Mongolia. The experts cited a dozen features of the bones, as well as their light color and even the dirt stuck in the cracks in the fossils, as characteristic of Tyrannosaurus bataar rather than the larger T. rex or other members of the tyrannosaur tribe.

Federal attorneys said that the importers set the skeleton's value at $15,000, but that a value of $950,000 to $1.5 million was listed in this year's auction catalog. They also said the 8-foot-tall (2.4-meter-tall), 24-foot-long (7.3-meter-long) skeleton was incorrectly listed on customs forms as consisting of assorted fossilized reptiles and skulls.

The complaint names Florida Fossils as the ultimate consignee for the imported goods, and notes that the company was owned at the time of importation by Eric Prokopi. The skeleton was shipped from Florida to Texas, and then on to New York in preparation for the May 20 sale. Soon after word spread that a million-dollar tyrannosaur was coming up for auction, representatives of the Mongolian government became interested and sought unsuccessfully to stop the sale.

The dinosaur skeleton is currently in the custody of Cadogan Tate Fine Art in Sunnyside, N.Y. In the weeks since the controversial sale took place, the auction house has let paleontologists and representatives of the Mongolian government examine the fossil.

"I thank and applaud the United States Attorney's office in this action to recover the Tyrannosaurus bataar, an important piece of the cultural heritage of the Mongolian people," Mongolian President Tsakhia Elbegdorj was quoted as saying in the U.S. government's news release about the case. "Cultural looting and profiteering cannot be tolerated anywhere, and this cooperation between our governments is a large step forward to stopping it."

My efforts to contact Prokopi today were unsuccessful, but representatives of Heritage Auctions issued this statement from the company's co-chairman, Jim Halperin:

"We auctioned the Tyrannosaurus bataar conditionally, subject to future court rulings, so this matter is now in the hands of lawyers and politicians. We believe our consignor purchased fossils in good faith, then spent a year of his life and considerable expense identifying, restoring, mounting and preparing what had previously been a much less valuable matrix of unassembled, underlying bones. We sincerely hope there will be a just and fair outcome for all parties."

More about the tyrannosaur:

• May 18: Auction stirs up a tussle over tyrannosaur
• May 21: Despite challenge, fossil sells for $1 million
• May 24: Auctioned dino skeleton believed to be smuggled
• June 8: Experts say tyrannosaur is definitely from Mongolia

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Mariana Ruiz Villareal

Calculations of dinosaur biomass suggest that plant-eating sauropods like the ones pictured here in an artist's conception could have contributed enough methane to warm Earth's climate 150 million years ago.

Some scientific findings are just too good to leave alone, even if you don't know if they can ever be confirmed: Such is the case for a study saying that plant-eating dinosaurs could have emitted enough digestive methane to warm Earth's climate 150 million years ago.

"It is known that the time of these dinosaurs was warmer than now," said David Wilkinson, an environmental scientist at Liverpool John Moores University who's the lead author of a paper on the subject appearing in the journal Current Biology. "This is explained usually by an enhanced greenhouse effect, mainly carbon dioxide. If we are correct, then methane from sauropods may have been a contributor to this greenhouse effect."

Methane is a more potent greenhouse gas than carbon dioxide, and modern-day livestock are thought to be responsible for about a quarter of the methane released in the United States. Some say that the belches and flatulence of cattle, pigs and sheep are a significant contributor to the warming effect caused by greenhouse-gas emissions. So why wouldn't it have been the same in the age of giant plant-eating dinosaurs, when global biomass density was at least several times what it is today?

"All vertebrates that feed on leaves, etc., use microbes to help digest these, and usually give off methane," Wilkinson told me in an email. "This includes both mammals and reptiles. ... Although details vary within groups, everything around today does this, so the assumption is [that] larger herbivorous dinosaurs did as well."

He and his colleagues ran the numbers, using what they saw as conservative estimates for the total amount of dinosaur biomass and methane production rates per kilogram of body mass. They came up with a figure of 520 million tons of methane emitted per year, which is more than total modern-day methane emissions from all sources, natural and industrial. The current estimate for total methane emission is around 500 million tons a year, with 50 to 100 milllion tons of that coming from ruminant animals such as cows and goats, Wilkinson said.

"Our work certainly suggests biology and climate were involved in a feedback loop," he said.

Biologists have found that most of the modern-day methane emissions from livestock come from belching rather than flatulence. Was it the same for dinosaurs? "We have no particular view which end of the sauropod the methane came out," Wilkinson told me. "Could be either or both."

Chemical analysis of ancient marine sediments has found that greenhouse-gas levels went through a huge rise 201 million years ago, around the time of a mass extinction that set the stage for the rise of the dinosaurs. Scientists suspect that the atmospheric methane levels at that time were pumped up by a massive release of methane from the seafloor. Such evidence suggests that plant-eating dinosaurs weren't responsible for starting the upswing in Mesozoic methane. But did they help preserve the methane-rich atmosphere and toasty temperatures until they were killed off by an asteroid strike?

Wilkinson noted that his paper was titled "Could Methane Produced by Sauropod Dinosaurs Have Helped Drive Mesozoic Climate Warmth?" — not "Did Methane Produced by Dinosaurs Help Drive Climate Warmth."

"What our simple calculations show is that, yes, it could. It's a real possibility. But we don't show that it did happen," he said. "That would require much more work, and indeed it may be impossible to completely prove this without a time machine."

Extra credit: A dozen years ago, the BBC quoted a Chinese news report that quoted an unnamed French scientist as saying the dinosaurs were wiped out 65 million years ago not by an asteroid, but by their own flatulence. This hypothesis proposed that the methane emissions from the giant beasts became so great that the climate changed, the vegetation withered and the dinosaurs all starved. But that's just too silly to consider. Or is it?

More about methane:

• U.S. claims success in fuel source test
• Herb quells cows' methane-laden belches
• Did methane 'burp' clear way for dinosaurs?
• Methane seeping from ice becomes climate concern

In addition to Wilkinson, authors of the Current Biology paper include the University of London's Euan G. Nisbet and the University of Glasgow's Graeme D. Ruxton.

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Mariana Ruiz Villareal

An artist's conception shows a pair of Alamosaurus sanjuanensis dinosaurs.

Here's a trivia question for your dino-crazy kids: What's the biggest dinosaur to roam North America? Paleontologists report that it's Alamosaurus sanjuanensis, one of many breeds of long-necked, long-tailed sauropods to roam the continent 69 million years ago.

Montana State University's Denver Fowler and the State Museum of Pennsylvania's Robert Sullivan make that judgment on the basis of two huge vertebrae and a femur that they collected in New Mexico between 2003 and 2006. Based on the bones' proportions, they figure that Alamosaurus could be around the same size as South America's giant sauropods, such as the 70-ton Argentinosaurus.

If  Fowler and Sullivan are correct, that'd make Alamosaurus twice as heavy as paleontologists thought it was just a few years ago. Their research was published Tuesday in Acta Palaeontologica Polonica. 

"Over the past 20 years, Argentinean and Brazilian paleontologists have been unearthing bigger and bigger dinosaurs, putting the rest of the world in the shade," Fowler said in an MSU news release issued Tuesday. "However, our new finds not only show that Alamosaurus is newly recognized as the biggest dinosaur from North America, but also that it was right up there with the biggest South American species: The U.S. is back in the fight for the No.1 spot."

There's more at stake here than mere bragging rights. "Our findings show that Alamosaurus was originally described based on immature material, and this is a problem, as characteristics that define a species are typically only fully gained at adult size," said Fowler, a doctoral student at MSU's Museum of the Rockies. "This means that we might be misinterpreting the relationships of Alamosaurus and possibly other sauropod dinosaurs too."

Researchers from MSU and the Pennsylvania museum are continuing to collect Alamosaurus bones to resolve the size question as well as other details about the dinosaurs' life and death. To keep up with the research — and perhaps eventually find out whether Alamosaurus pushes aside Argentinosaurus and its Russian rival, Ruyangosaurus, check in with the Facebook page for the Horner Paleo Lab at the Museum of the Rockies. You can also check out this video about the Alamosaurus quest:

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

When viewers tune in to Fox's "Terra Nova" time-travel TV series, premiering tonight on Fox, they'll see an 85 million-year-old world that's pretty much "terra incognita" for dinosaur experts. And that's just fine with world-famous paleontologist Jack Horner.

"I suggested 85 million, because it's a time that we know the least about, and it's kind of in the middle of the Cretaceous period, which means we could bring some older dinosaurs forward and take some younger dinosaurs back without getting in too much trouble," Horner told me.

So even though the long-necked, plant-eating dinosaur known as Brachiosaurus died out long before Tyrannosaurus rex came onto the scene, their cousins can mix it up in the computer-generated landscape created for "Terra Nova."

"We just cannot use a T. rex, but there are tyrannosaurs, so we can certainly create an animal that looks very similar to T. rex," Horner said.

Tonight's premiere raises the curtain on a series that some critics have characterized as a cross between "The Lost World" and "Lost," with a flashy "Stargate" time portal and an extra dash of "Swiss Family Robinson" thrown in. There are family dramas, shadowy conspiracies and seemingly indecipherable rock markings to stir the pot, but the success of the mega-expensive series arguably depends on the dinosaurs — just as it did for the "Jurassic Park" movie series.

Horner is familiar with the terrain — not only because of his roles as curator of paleontology at Montana's Museum of the Rockies, professor at Montana State University and one of the world's foremost fossil-hunters, but also because he was a consultant for "Jurassic Park" and a model for the movie's alpha-scientist character.

Steven Spielberg, co-executive producer for "Terra Nova," was the one who brought in Horner as a consultant for the "Jurassic Park" movies. "I guess he liked what I did there, so [the TV show's producers] called and asked if I could do it" for "Terra Nova" as well, Horner recalled.

Horner works with the artists and the writers on the dino concepts. "My job really is to make sure the dinosaurs are as accurate as they can be, even if we invent them," he said. "If they're going to be raptorlike dinosaurs, they have to have the characteristics of a raptorial dinosaur ... but when it comes to headgear, we can do a lot of things."

Slasher movie
That last comment relates to the first dinosaur invented for the series: a nasty critter referred to as the "Acceraptor" and nicknamed the "Slasher."

"He's got some characteristics that are new, but still within the realm of possibility," Horner said. "The only detail I can tell you is, it's going to be a scary dinosaur. Let's put it this way: I wouldn't want to be in the forest with a Slasher, especially at night."

Further details have seeped out through the dinosaur blogs: The Slasher sports some gaudy headgear that Brian Switek, who blogs about paleontology for Smithsonian magazine and Wired, has criticized as a "horribly lame" look (see below for more). It has some fearsome-looking claws, but its deadliest weapons are the sharp barbs that whip around at the end of its yards-long tail. "As far as I know, that's totally made up," Bob Strauss, who manages About.com's guide to dinosaurs, told me.

Horner said he's willing to give the writers and artists wide latitude when it comes to dreaming up dinosaurs. "If we know something for sure, then we'll keep it within the bounds of science," but if there are blank spaces in the scientific picture, a little (or a lot of) imagination is allowed. This is Hollywood, after all.

"Just like the people in the movie, the dinosaurs are actors. They will go faster than we think dinosaurs can go," Horner admitted.

Food for thought for dino fans
That was the case for "Jurassic Park," and Horner is hoping that "Terra Nova" will offer even greater dramatic possibilities, for the dinosaurs as well as for the human actors.

"It's one thing to make a movie. Movies are two hours of a single story," Horner said. "The really cool thing about 'Terra Nova' is that it is a series, so we have the capability of building and building and building on it, each time seeing new animal and plant characters and still being able to follow the family that the story is about. In many ways, it's a lot better than a movie, just on a smaller screen."

And if dinosaur fans want to argue over the finer points of the dinosaur depictions, that's just fine with Horner, too. "If people are watching and paying attention like that, that would be great," he told me.

Here are some of the reviews from experts who are paying attention:

• University of Maryland paleontologist Thomas Holtz, who wrote the official "Jurassic Park" dinosaur guide and has consulted on many dinosaur documentaries, including the Discovery Channel's "Dinosaur Revolution":

The main reason why the "Terra Nova" colonists go through a rupture in space-time is because the world has become an environmental wasteland by the year 2149. People have to wear "re-breathers" on their faces to cope with the polluted air. But Holtz noted that the world of 85 million B.C. wasn't exactly a breath of fresh air, either.

"If you're trying to escape climate change by going back to the past, you wouldn't want to go back to 85 million years ago, where CO2 is almost 1,000 parts per million, as opposed to 392 at present," he observed. Holtz acknowledged, however, that an elevated carbon dioxide level isn't the only environmental problem facing the smoggy, run-down world of 2149.

As for the dinosaurs, Holtz had a couple of pieces of advice for the writers. First, don't get too specific about the dinosaur names. Instead of referring to Brachiosaurus (the long-necked plant-eater that makes an early appearance on tonight's show) or Carnotaurus (the toothy, horned dinosaur that almost runs down Terra Nova's patriarch in the episode), use more generic names (brachiosaurs or abelisaurs, respectively). There's no evidence that either Brachiosaurus or Carnotaurus was around 85 million years ago, but it's plausible to claim that their distant cousins were.

"Saying it more generically is safer," Holtz said.

Also, as the series goes on, Holtz hopes the writers get the locale right. For example, no Carnotaurus fossils have been found in North America, so if the series claims that the "Terra Nova" colonists are settling in Cretaceous Chicago, coming upon Carnotaurus' older cousins there would be "as unlikely as encountering a koala in Montana," Holtz said.

Most of the TV audience might not care that much about the terminology, but it's better to have the dino-geeks for you than against you. "They get mad enough with the dinosaur documentaries," said Holtz, speaking from experience.

• Science writer Brian Switek, author of Smithsonian's Dinosaur Tracking blog and the book "Written in Stone: Evolution, the Fossil Record and Our Place in Nature." Here's Switek's pithy email critique of the "Terra Nova" dinos:

"All I have seen of the 'slasher' is the promotional artwork, but, yes, I'm sorry to say that the creature design for the dinosaur is horribly lame. The poor creature looks as if the special effects artists took one of the Jurassic Park raptors, stuck a crest from an oviraptorid dinosaur on its head, and then gave it a bad toupee. So many fantastic and terrifying dinosaurs have been found — dromaeosaurs with double sickle-claws (Balaur), Allosaurus-cousins with sail backs (Concavenator), crocodile-snouted hunters (Baryonyx), and others — that the I think the show's creators would have done better to draw inspiration from actual dinosaurs rather than trying to dress up a Deinonychus.

"Then there's the scientific issue. Thanks to multiple discoveries of feathered dinosaurs during the past 15 years, we know beyond a shadow of a doubt that many coelurosaurs — the group to which raptors, tyrannosaurs, oviraptorids and others belong — were at least partly covered in feathers. Even Velociraptor arm bones have been found with quill knobs for the attachment of feathers! (The significance of this is that we can now detect the presence of feathers on some dinosaurs even if the feathers themselves are not preserved.) Therefore, the 'slasher' should be a feathery beast and look less like a dinosaur with a comb-over. Every year more feathered coelurosaurs are found, and it's time that television shows and movies featuring these dinosaurs restore the animals with their full plumage. ...

"It is true that our knowledge of dinosaur life around 85 million years ago (the beginning of the Santonian age) is relatively limited. Compared to what we know about the later Campanian (83 million to 70 million years ago) and Maastrichtian (70 million to 65 million years ago) ages, the world of dinosaurs during the Santonian is still fuzzy and waiting to be fleshed out by new discoveries. That said, I don't have a problem with a show creating new dinosaurs or even bringing in dinosaurs from slightly older or younger time periods. (If I recall correctly, Carnotaurus — a Campanian dinosaur from prehistoric Argentina — is in the show.) Sometimes scientific accuracy needs to be bent a little to make compelling television. That's just the way it goes when you want to tell a story.

"Nevertheless, I don't think any imaginary dinosaur can really compare to the real animals we're finding. Spielberg and the show's co-creators can dream up as many dinosaurs as they want, but, to me, speculative creatures like the slasher are always going to pale in comparison to the bizarre array of wonderful dinosaurs paleontologists have uncovered."

Science writer Bob Strauss, dinosaur guide for About.com, who saw an advance screening of "Terra Nova" and discusses it in a review:

Strauss said "Jurassic Park" stirred up a lot of controversy on the subject of dinosaur verisimilitude. For example, real Velociraptors were nowhere near smart enough or agile enough to turn a doorknob, and pterosaurs weren't strong enough to carry off a kid.

"Terra Nova" could well do the same, and not just because of slasher's barb-whipping tail. Did brachiosaurs really eat small lizards, or were they strictly herbivores? Shouldn't the TV series' Carnotaurus have arms as wimpy as the real thing? Where's the slasher's hind-foot claw?

But judging by the first show, Strauss thinks dino-geeks will stick with the series, if for no other reason than to get their weekly Cretaceous fix and debate how the Hollywood monsters compare with the real things. "They're just so happy to have dinosaurs on TV," he told me.

More about dinosaurs in fact and fiction:

• 'Dinochicken' scheme puts evolution in reverse
• Fox sees family, not sci-fi, at heart of 'Terra Nova'
• Spielberg: 'Jurassic Park 4' coming in a few years
• Search for Cretaceous dinosaurs on msnbc.com 

Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding me to your Google+ circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.

The way David Attenborough sees it, pterosaurs and 3-D documentaries were made for each other, even though they're separated by 65 million years.

"You want to have something that moves not just in 2-D across the ground, but goes up as well," he said. That makes the flying reptiles an "obvious subject" for a 3-D movie, Attenborough added.

He should know: The 85-year-old British broadcaster and naturalist has been doing nature documentaries for the BBC for more than 50 years — and what's more, he's the brother of Richard Attenborough, the actor who welcomed scientists to "Jurassic Park" in that classic 1993 dino-flick.

So it's hard to think of anyone better-suited to be the writer and narrator of "Flying Monsters 3D," a big-screen documentary due for its North American opening on Oct. 7.

The movie, which had its British theatrical release earlier this year, blends computer-generated graphics with field trips to fossil beds and laboratories. In the process, a wide variety of pterosaur breeds are virtually resurrected.

Paleontologists say the creatures came to dominate the skies of the Cretaceous era, just as dinosaurs dominated the land below. "The story of how that came about, and why eventually they died out, is what the film is about," David Attenborough told journalists during a Monday teleconference.

The 3-D special effects in "Flying Monsters" take their cue from "Avatar," but there's much more mixing of the Cretaceous and the modern world. At one point, pterosaur bones laid out on a table assemble themselves and take off. And during one of the movie's concluding scenes, a Quetzalcoatlus with a 40-foot wingspan pulls alongside Attenborough as he's sitting in the cockpit of a glider.

Atlantic Productions / ZOO

A long-extinct pterosaur known as Quetzalcoatlus seems to fly alongside host David Attenborough in a digitally created scene from "Flying Monsters 3D."

"I originally thought I might do that in a hang glider. ... Unfortunately, the insurers wouldn't let me do that, so I had to do it in the glider," he quipped.

Attenborough said one of the challenges of the project was to make sure the movie stuck to the scientific story instead of turning into a 3-D monster chiller horrorfest. "It's no good just doing a film to say, 'Oh, yes, it's wonderful in 3-D,' but have no story behind it," he said.

The scientific story
Pterosaurs have been the subject of scientific debate for decades: Paleontologists have argued over whether they were cold-blooded or warm-blooded, whether they bore feathers or fur, whether they could take off from a runway or had to jump off a cliff in order to take flight. (One of the places Attenborough visited during the making of the movie was the famed "pterosaur landing strip" in southern France, which he compared to "a prehistoric Heathrow" airport.)

The creatures shown in "Flying Dinosaurs 3D" aren't your father's pterosaurs: They use their folded wings as forelimbs when they walk around on all fours — or when they launch into the air. Some have a coat of fine hairs known as pycnofibers, which serve as evidence that they were warm-blooded. And most of them sport colorful crests, which Attenborough considers a "reasonable" hypothesis.

"They were almost certainly colored, and they had structures on their heads which can best be explained as being like the crest of a bird, and were used in courtship," he said.

Atlantic Productions / ZOO

A crested pterosaur known as a Tapejara uses its folded forelimbs as it prepares for take-off in a scene from "Flying Monsters 3D."

Were pterosaurs actually birds? Pterosaurs had wings. (Check, although their wings could spread wider than bird wings.) They laid eggs. (Check, although their eggs were more like those of reptiles than modern-day birds.) They tended to group in colonies, as many species of birds do today. Pterosaurs and early birds co-existed during the Cretaceous ... but the mainstream view is that they came from different lines of the evolutionary tree.

Why did birds survive while pterosaurs die out? That's the 65 million-year question.

"Birds had feathers, stiff quills, but pterosaurs didn't have feathers," Attenborough said. "They didn't evolve feathers."

Instead, pterosaurs got their lift from membranes that were attached to their limbs and spread out during flight. Those membranes made it "very difficult to move around on the ground in a nimble sort of way," while birds "were able to run on the ground very well," Attenborough said. The way he sees it, that was a "crucial element" in the fight for survival when the era of the dinosaurs ended.

The rest of the story
Is that the way paleontologists see it? Mark Witton, a pterosaur expert at the University of Portsmouth, was one of the scientists who served as consultants for the film — and he was invited to a screening when the British version was ready for its release. "My hopes were high that everyone's favourite leathery-winged beasties were about to get their moment in the media sun," he wrote on the Pterosaur.net blog.

Atlantic Productions / ZOO

Dimorphodon flies through a jungle setting in a scene from "Flying Monsters 3D."

He came away impressed by the film's technical fireworks, but not so much impressed by the scientific claims. "Take, for instance, the way that we're explicitly told that pterosaurs were out-competed by birds and their ability to adapt to new ecologies, thus sealing the extinction of the more evolutionary-stagnant pterosaurs," he wrote. "Detailed analyses of bird and pterosaur diversity have either proved inconclusive on this issue ... or categorically stated that there's no evidence for bird-driven pterosaur extinction. ..."

Witton catalogs the movie's other scientific sins with the rigor that only a dedicated specialist could muster. "It really seems that, with a bit more care, this could've been as much of an achievement for effective scientific communication as it has been for 3-D technology, but it's really an enormous missed opportunity," he wrote.

Other pterosaur experts have provided more positive reviews. The University of Leicester's David Unwin, who was also a consultant for the film, praised the results in a video clip. "Films like this do a tremendous job of actually communicating in a really exciting way, and one that grabs your attention, the kinds of things that we've found out about pterosaurs," he said. "And what I really love is being able to see the animation and being involved in the process of trying to produce the best possible and most accurate animations."

What's a pterosaur fan to do? If you go see "Flying Monsters 3D," you'll want to sit back and enjoy the 3-D effects ... and then get the rest of the story from online resources such Pterosaur.net, or Dave Hone's Archosaur Musings, or John Conway's Palaeontography, or Pterosauria at the University of California Museum of Paleontology.

More about pterosaurs:

• Pterosaurs were 10 times heavier than biggest birds
• Flying reptile's big bill drags down feeding myth
• Pterodactyls in Japan hung out with birds
• How did flying reptiles rise?
• Search for pterosaurs on msnbc.com 

Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding me to your Google+ circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.    

Xing Lida and Liu Yi

An artist's conception shows how the birdlike dinosaur known as Xiaotingia zhengi might have looked.

The newfound fossil of a 155 million-year-old feathered dinosaur has led scientists to claim that Archaeopteryx, the species long held forth as the "oldest bird," is no bird at all.

Chinese researchers made the claim in Thursday's issue of the journal Nature, and an outside expert says the study "is likely to rock the paleontological community for years to come." Ohio University paleontologist Lawrence Witmer noted that the latest research, focusing on a fossil species dubbed Xiaotingia zhengi, comes 150 years after the discovery of Archaeopteryx, which marked a milestone in the study of the origin of birds.

"It's fitting that 150 years later, Archaeopteryx is right back at center stage," Witmer told me.

Xiaotingia was found by a collector in China's Liaoning Province, a hotbed for feathered-dino fossils, and sold to the Shandong Tianyu Museum of Nature. Paleontologists led by Xing Xu of the Chinese Academy of Sciences analyzed the fossil's skeletal measurements in detail and fed them into a computer database with  measurements from 89 fossilized dinosaur and bird species, including Archaeopteryx.

Without Xiaotingia, the computer analysis put Archaeopteryx on the evolutionary line leading to modern-day birds. But when Xiaotingia was included, Archaeopteryx was placed in a group of birdlike dinosaurs known as deinonychosaurs. The differences had to do with details such as the shape of the wishbone and the skull's snout.

Archaeopteryx was about the size of a modern-day crow, and Xiaotingia was as big as a chicken.

Xu et al., Nature

The fossil skeleton of Xiaotingia zhengi is splayed out in rock.

"If you just looked at Xiaotingia, you'd say, 'Oh, boy, another little feathered dinosaur from China,'" Thomas Holtz, a paleontologist at the University of Maryland at College Park who reviewed the study for Nature, told me. "In and of itself, it is not a particularly unusual animal. But the combination of traits, at least in their analysis, pulls Archaeopteryx over to the deinonychosaur side of things."

The researchers acknowledged that their reclassification was "only weakly supported by the available data," but they said this kind of fuzziness was to be expected when the fossils being analyzed are close to the common ancestor of now-extinct dinosaurs and modern birds. "This phenomenon is also seen in some other major transitions, including the origins of major mammalian groups," they wrote.

Witmer agreed: "We're looking at an origin, and consequently it's going to be messy."

The 150 million-year-old Archaeopteryx fossil, which was discovered in southern Germany in 1861, was long seen as the oldest evidence of a bird species because the rocky imprint bore traces of feathers. But over the past decade or two, many dinosaur fossils have been found with evidence of feathers — to the extent that some scientists have been able to figure out how the feathers were colored. As a result, some researchers have argued for years that Archaeopteryx should be reclassified.

In the past, creationists have used Archaeopteryx in their arguments against evolutionary theory, contending that birds always existed in their feathered form and did not evolve from dinosaurs. Evolution's critics may try to spin these latest findings to their advantage as well, Witmer said.

"It may well be they're going to suggest that we evolutionists don't know what we're doing," he told me. "In reality, it's just the opposite. It just shows what evolution is all about. A prediction of evolutionary theory is that it should be really hard for us to figure out what's going on in an origin."

Archaeopteryx's dethronement means the title of "oldest bird" could fall to other ancient species, such as Epidexipteryx hui, Jeholornis and Sapeornis, Witmer said. "They're not exactly household names," he noted. "These new characters have been known only for 10 years or less." Archaeopteryx, meanwhile, would be lumped in with Xiaotingia as well as another feathered-dino species called Anchiornis huxleyi.

G. Mayr / Senckenberg

An Archaeopteryx specimen highlights wing and tail feather impressions.

The renewed debate over Archaeopteryx's classification is far from finished. Holtze said he knew some researchers who were inclined to go with a completely different classification scheme, which would put the deinonychosaurs along with Archaeopteryx on the evolutionary line leading to modern-day birds.

The debate could also require a rethinking of how birds arose, and how features such as feathers and flight developed. Holtz said some paleontologists have suggested that Archaeopteryx was not a particularly good flier, and putting it in the deinonychosaur category would make more sense on that score. It may turn out that deinonychosaurs gradually evolved from so-so fliers into feathered but flightless animals. "They would have been nasty predatory analogs to ostriches," Holtz said.

Holtz acknowledged that Archaeopteryx "has been our image of what early birds are like, for the historical reason that it's been known for 150 years as having all these feathers." The fact that the fossil was found just two years after Charles Darwin published "On the Origin of Species" added to its image as an evolutionary icon. A dramatic change in that image might come as another scientific shock to folks who are already being told that there's no such thing as a brontosaur, and that Pluto no longer ranks among the solar system's major planets.

"To which I say, 'Get over it!'" Holtz said. "Science is about changing ideas based on evidence, not about ignoring evidence to conform to our comfortable ideas."

More about birds and dinosaurs:

• Are dinosaurs alive?
• From 1999: Debating a dinosaur detective story
• Gallery: Nine links in the dinosaur-bird transition
• T. rex analysis supports dinosaur-bird link

In addition to Xu, the authors of the Nature report, "An Archaeopteryx-like Theropod From China and the Origin of Avialae," include Hailu You, Kai Du and Fenglu Han. Witmer is the author of a commentary in Nature titled "An Icon Knocked From its Perch."

Connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. You can also add me to your Google+ circle, and check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds. 

Carin L. Cain / AAAS / Science

An artist's conception shows a typical sauropod with a long neck, long tail and massive body.

How warm was a dinosaur's blood? Researchers report that it was about as warm as ours, based on a chemical analysis of sauropod teeth, of all things. The novel findings, published today by the journal Science, are consistent with the view that at least some dinosaur species were warm-blooded — and suggest a way to settle the controversy conclusively.

"What we're basically doing is sticking a thermometer up a dinosaur's butt," study co-author John Eiler, a geochemist at Caltech, told me jokingly.

What the researchers actually did was to drill out samples of fossilized tooth enamel from an assortment of sauropods, the largest kind of dinosaurs. Then they analyzed how different isotopes of carbon and oxygen were bonded together in apatite, a rare form of carbonate found in the enamel.

Past experiments have shown that the heavier isotopes — carbon-13 and oxygen-18 — are more likely to clump together when the carbonates are formed at lower temperatures. At higher temperatures, the bonds are more randomly distributed, and you don't see as many of the heavy isotopes clumping together. The precise proportion of the clumped isotopes can tell you the average body temperature of a toothy organism.

"This is the basis of the 'thermometer,' but it's a thermometer where all the information that allows you to rigorously calculate temperature is preserved in a single phase," Eiler said.

He said clumped-isotope thermometry has been tested with teeth from sharks, birds, crocodiles, rhinos and elephants, "and it just works for all of them." The procedure was also tried on a woolly mammoth's 20,000-year-old teeth and the 12 million-year-old teeth of an ancient crocodile and rhino. But this is the first time results have been reported from 150 million-year-old dinosaur teeth.

The analysis was done on 11 teeth from Brachiosaurus and Camarasaurus dinosaurs from Tanzania, Oklahoma and Utah. Other samples were judged unsuitable for the sensitive chemical tests. "Did we do it perfectly?" Eiler said. "We believe that we found a result that we're confident in, but it's not easy."

Luis Chiappe, director of the Dinosaur Institute at the Natural History Museum of Los Angeles County, told me in an email that the findings were "quite interesting and promising."

Warm blood ... but warm-blooded?
It turns out that the temperature Eiler and his colleagues came up with — 36 to 38 degrees Celsius, or 97 to 100 degrees Fahrenheit — is consistent with previous estimates produced by other methods. But Eiler said those methods, including one that involves comparing the different oxygen isotopes in dinosaur teeth, resulted in less direct measurements.

"None of those are simple applications of a thermometer," he said. "They all require some kind of assumption about the nature of the body fluid that the structure grew from."

The key point behind the research isn't necessarily that dinosaurs had blood as warm as ours. "The deeper question is, how did they get that way?" Eiler said. "What allowed them to get to that temperature? Was it through regulation of their metabolism, like it is for us? Was it simply their size? This is the next step."

Some scientists hold to the view that dinosaurs as a group might not have been strictly warm-blooded (like today's birds and mammals) or cold-blooded (like most reptiles). They suggest that some dinosaurs were big enough to keep their blood warm due to thermal inertia — as alligators and Galapagos tortoises do.

Eiler said the newly published temperature estimates are not consistent with that hypothesis. "They're not as hot as they were supposed to be," he said, "and that tells us there's something about dinosaur physiology that we don't understand."

To get at the answer, the scientists want to take lots more temperature readings, using the tooth enamel from big and little dinosaurs: from juvenile sauropods and dwarf sauropods, as well as from another class of dinosaurs known as theropods, which include Tyrannosaurus rex and are thought to be more closely related to birds.

"If sauropods were like mammals, you would expect the small animals to have the same body temperature as the large ones," Caltech biologist Robert Eagle, the Science study's lead author, told me. But if the temperature readings vary significantly, that would tip the scales back toward the thermal-inertia hypothesis — or it might force scientists to come up with a whole new hypothesis.

Beyond dinosaurs
And that's just the start. "When you start to think about the evolutionary transition between dinosaurs and birds, maybe you can interrogate these evolutionary transitions and find out when warm-bloodedness arrived," Eagle said. "We have no idea when that happened."

If it turns out that dinosaurs were truly warm-blooded, scientists could work their way backward toward the common ancestor of dinosaurs and crocodiles, to study how body temperature regulation might have evolved during the Permian geologic period, more than 250 million years ago. "The only limitation is whether there's enough well-preserved fossil material," Eagle said. "That doesn't necessarily depend on age. ... It's definitely theoretically possible that we can go all the way back to the Permian."  

Eagle said the clumped-isotope thermometer has already been used on rocks and the shells of marine organisms to study ancient climate change, and now it's being applied to a meteorite from Mars as well. In that experiment, researchers want to find out "whether this meteorite experienced high temperatures on the journey from Mars to Earth," he said. If there's no evidence of high temperatures, that might support claims that organisms could make their way between the planets inside such meteorites — an idea that set off a storm of controversy earlier this year.

Eiler said we'll probably be hearing much more about this temperature-taking technique in the years to come: "It's still recent enough and exotic enough that you wouldn't quite want to call it mature, but it's established. ... Applying it to teeth, I think our lab remains unique in doing that, although I'm sure other labs will be doing it soon."

Update for 11:45 p.m. ET: I followed up with a phone call to Luis Chiappe, the dinosaur expert at the L.A. museum, and he said there may well be other applications for this technique. "I would imagine that the way it happens is, people realize there's a new tool on the table and they will grab it and use it in various ways." For example, Chiappe is an expert on dinosaur eggs, and it's not unthinkable that you could measure egg temperatures to investigate how dinosaur moms hatched their young. Modern-day crocodiles use temperature to determine the sex of their hatchings. Did dinos do the same?

Chiappe agrees that the next task is to test other sizes of dinosaurs.

"If we were to find comparable temperatures in hatchlings of sauropods and juveniles of sauropods, that would definitely support the idea that these animals were endotherms [warm-blooded]. So that needs to be done," he said. "The problem is that the technique is a destructive technique. Therefore, not too many museum curators will be happy to donate their specimens to be destroyed."

More about dinosaur physiology:

• How dinosaur proteins could have survived
• How to tell male from female dinosaurs
• Dinosaurs were taller due to thick cartilage
• Most dinosaurs were more like Barney than T. rex
• Teen pregnancy affected dinosaurs, too
• Tooth marks suggest T. rex was a cannibal 
• Search for dinosaurs on msnbc.com

"Dinosaur Body Temperatures Determined from Isotopic (C13-O18) Ordering in Fossil Biominerals" was published today on the journal Science's website and will appear in a future issue of the print version. In addition to Eagle and Eiler, the authors include Thomas Tütken, Taylor S. Martin, Aradhna K. Tripati, Henry C. Fricke, Melissa Connely and Richard L. Cifelli.

You can connect with the Cosmic Log community by "liking" the log's Facebook page or following @b0yle on Twitter. Also, give a look to "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

Rachel Simon

An artist's conception shows the sail-backed creature known as Xilousuchus sapingensis, which existed 247 million to 252 million years ago. A new analysis of fossilized Xilousuchus bones suggests that crocodiles diverged from birds and dinosaurs earlier than some experts previously thought

A fresh analysis of a fossil found in the 1970s suggests that the family trees for crocodiles, birds and dinosaurs diverged earlier than some may have thought.

The study represents the latest chapter in a long-running debate over the relationships between dinosaurs and the ancestors of two dissimilar types of modern-day creatures — crocs and birds.

Paleontologists have traced the ancestry of all three groups to a category of common ancestors called archosaurs. The archosaurs and their cousins lived around the time of Earth's deadliest die-off, the Permian-Triassic extinction, around 252 million years ago. Teasing out the details of the archosaurs' family tree is key to understanding how birds, dinosaurs and crocodiles are linked.

"This is one of the most interesting evolutionary questions in paleontology: the origin of birds in the broadest sense," Spencer G. Lucas, curator of paleontology at the New Mexico Museum of Natural History, told me today. "If you take crocodiles, birds and dinosaurs, how do you think that evolutionary tree came together?"

Most experts say birds could actually be considered the modern-day descendants of dinosaurs, while a relative few insist that dinosaurs were more closely related to crocodiles.

Second look at fossils from China
The new analysis, published on Tuesday in Earth and Environmental Science Transactions of the Royal Society of Edinburgh, focuses on the fossilized remains of a creature unearthed in China, known as Xilousuchus sapingensis. The specimen, consisting of a partial skull and 10 neck vertebrae, has been dated to the Early Triassic (252 million to 247 million years ago).

Xilousuchus was originally classified as a distant offshoot of the archosaur tree, known as Proterosuchia, and was thus thought to shed little light on the bird-croc-dino relationship. But the revised analysis puts it closer to the center of the archosaur family tree, and tending toward the crocodile side of an evolutionary split. Birds and dinosaurs would be on the other side of that split, said Sterling Nesbitt, a postdoctoral researcher at the University of Washington who led the research team.

The technique that was used for the analysis involved making detailed measurements of features in the fossilized bones. For example, if a fossilized specimen shows the hallmarks of a wing, that could lead scientists to classify the fossil as belonging to a bird.

"We used the same kind of reasoning for all the little features on the bones where the muscles attach, and we score it into this computer program and it tells us how these creatures are related," Nesbitt explained. "Once you put it into this context, it all falls together. ... Xilousuchus is our oldest evidence of an archosaur in the fossil record."

What it all means ... or maybe not
The fact that the main group of archosaurs showed signs of divergence so soon after the Permian-Triassic extinction suggested to Nesbitt and his colleagues that there might be a linkage. "It could have been that the Permian extinction triggered the rise of archosaurs because they filled a niche that was emptied by the extinction," he told me. "This is one possibility that we're looking into now."

Just as the demise of the dinosaurs led to the rise of mammals 65 million years ago, the earlier mass extinction may have contributed to the rise of the dinosaurs 250 million years ago, Nesbitt said.

At the New Mexico museum, Lucas said he wasn't sure the case was that clear-cut. There are so few specimens from the Permian-Triassic transition that the criteria for classification are still subject to debate, and it would be easy to make too much out of the fine distinctions between one fossil and another. "Some of this is merely semantics," he said.

"This is an interesting idea," he told me, "but I await the next analysis of the evolutionary relationship. All of this is really in flux."

Update for 10 p.m. ET: I heard back via email from Thomas Holtz, a paleontologist at the University of Maryland and author of "Dinosaurs," a dino-encyclopedia. Here's what he had to say:

"Although I haven't read the paper yet, the conclusions seem sound. That is, Nesbitt and his colleagues have closely re-examined a lot of the Triassic archosaurs and other archosauriforms (what we used to call 'thecodonts' in the old days, until it was recognized that 'thecodonts' just meant 'any poor archosauriform unlucky enough not to be a crocodilian, pterosaur, or dinosaur'), and have the biggest phylogenetic analyses of these guys out there.

"Xilosuchus falls out as a member of the poposauroids in their studies, an odd assemblage of croc-relatives (some look a lot like finned proto-mammals like Dimetrodon; others look superficially like dinosaurs).

"Because it is a poposauroid, that means that the common ancestor of all poposauroids, and of all pseudosuchians (all archosaurs closer to crocodilians than to birds) must have already been present. And if Pseudosuchia is present, its sister group Avemetatarsalia (birds and everything closer to birds) has to be present in at least its most primitive state.

"Now the avemetatarsalians at this time wouldn't be birds, or theropods, or even dinosaurs. In fact, Avemetatarsalia probably had not yet split into Pterosauromorpha and Dinosauromorpha. But it does mean that the lineages which would ultimate lead to alligators on one side and eagles on the other had already diverged in the earliest days of the Triassic." 

Correction for 11:40 a.m. ET May 19: I scrambled up the comparison of crocodiles to dinosaurs in the original text, but have fixed that. Sorry about the mix-up.

More on the bird-dino-croc debate:

• Interactive: Are dinosaurs alive?
• Gallery: Nine links in the dino-to-bird transition
• Dinosaurs had wrists like birds
• How dinosaurs handed down their fingers
• Hunchbacked dinosaur strengthens bird-dino link

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