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How to Weigh a Dinosaur

According to one new study, Stegosaurus youngsters were rather full-figured . 

The most complete skeleton known from this distinctive dino belongs to “Sophie,” a juvenile at London’s Natural History Museum. Despite her adolescence, she was an enormous animal, measuring 5.6 meters (18.3 feet) long from end to end.

So how much did Sophie weigh? No less than a whopping 3530 pounds, PhD researcher Charlotte Brassey said in a recent press release. If spot-on, her measurement would put the Stegosaurus on par with white rhinos and certain BMWs.

By the way, this is no off-the-cuff guesstimate. Brassey and two colleagues meticulously scanned all 360 of Sophie’s beautiful bones to create a digital model of her skeleton. As Brassey explains, “very simple shapes” were then digitally wrapped “around her body outline, and … that whole body volume [was used] to predict body mass.”

We’ve never had a sure-fire means of figuring out just how heavy long-extinct animals were. And unless someone invents a time machine that doubles as an extra-large bathroom scale, we never will. But even taking educated guesses has proven difficult, thanks largely to anatomical x-factors (how beefy, for example, was T. rex’s tail?).

When zoologist Robert McNeill Alexander attacked this problem during the 1980s, he wielded an unlikely tool: plastic dinosaur models. Donning his best Archimedes impression, Alexander submerged reasonably up-to-date miniatures in water and measured the displacement. Afterwards, he more or less scaled up these results based on each species’ real-life dimensions. This simple approach provided rough tonnage estimates for a variety of dinos. But hindsight hasn’t been kind to Alexander’s models, which—among other things—featured several inaccuracies (neck length, limb girth, etc.) that seriously skewed his data.

A far more popular technique involves femurs, or “thighbones.” In the animal kingdom, there’s a general correlation between femur circumference and total body mass—though the fact that, like birds, many dinosaurs had hollow limb bones does complicate matters.

Still, the challenge is worth grappling with. As Brassey points out, only by doing so can paleontologists answer basic questions about dinosaurian lifestyle and behavior. “If [you] want to estimate how fast an animal runs, you need body mass,” she said. “If you want to say something about … metabolism, you need to know the body mass.”

This brings us back to digital Sophie, who won’t be sitting idly by as Brassey pursues her next project. Instead, she’ll have her virtual beastie hitting the treadmill. “[Now] what I’m looking to do is begin to strap muscles on to our computer models so that we can get her walking to say something about locomotion,” she said.

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The T. Rex Fossil That Caused a Scientific Controversy
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iStock

In the early 2000s, a team of paleontologists inadvertently set the stage for a years-long scientific saga after they excavated a well-preserved partial Tyrannosaurus rex skeleton from Montana's Hell Creek formation. While transporting the bones, the scientists were forced to break a femur. Pieces from inside the thigh bone fell out, and these fragments were sent to Mary Schweitzer, a paleontologist at North Carolina State University, for dissection and analysis.

Under a microscope, Schweitzer thought she could make out what appeared to be cells and tiny blood vessels inside the pieces, similar to those commonly discovered inside fresh bone. Further analysis revealed what appeared to be animal proteins, which sent Schweitzer reeling. Could she have just discovered soft tissue inside dinosaur leg bone many millions of years old, found in ancient sediments laid down during the Cretaceous period? Or was the soft stuff simply a substance known as biofilm, which would have been formed by microbes after the bone had already fossilized?

Following a seemingly endless series of debates, studies, and papers, Schweitzer's hunch was proven correct. That said, this contentious conclusion wasn't made overnight. To hear the whole saga—and learn what it means for science—watch the recent episode of Stated Clearly below, which was first spotted by website Earth Archives.

[h/t Earth Archives]

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Fossilized Poop Shows Some Herbivorous Dinosaurs Loved a Good Crab Dinner
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Lead author Karen Chin of the University of Colorado Boulder
Courtesy the University of Colorado Boulder

Scientists can learn a lot about the prehistoric world through very, very old poop. Just recently, researchers from the University of Colorado-Boulder and Kent State University studying fossilized dinosaur poop discovered that some herbivores weren't as picky about their diets as we thought. Though they mostly ate plants, large dinosaurs living in Utah 75 million years ago also seem to have eaten prehistoric crustaceans, as Nature News reports.

The new study, published in Scientific Reports, finds that large dinosaurs of the Late Cretaceous period seem to have eaten crabs, along with rotting wood, based on the content of their coprolites (the more scientific term for prehistoric No. 2). The fossilized remains of dinos' bathroom activities were found in the Kaiparowits rock formation in Utah's Grand Staircase-Escalante National Monument, a known hotspot for pristine Late Cretaceous fossils.

"The large size and woody contents" of the poop suggest that they were created by dinosaurs that were well-equipped to process fiber in their diets, as the study puts it, leading the researchers to suggest that the poop came from big herbivores like hadrosaurs, whose remains have been found in the area before.

Close up scientific images of evidence of crustaceans in fossilized poop.
Chin et al., Scientific Reports (2017)

While scientists previously thought that plant-eating dinosaurs like hadrosaurs only ate vegetation, these findings suggest otherwise. "The diet represented by the Kaiparowits coprolites would have provided a woody stew of plant, fungal, and invertebrate tissues," the researchers write, including crabs (Yum). These crustaceans would have provided a big source of calcium for the dinosaurs, and the other invertebrates that no doubt lived in the rotting logs would have provided a good source of protein.

But they probably didn't eat the rotting wood all year, instead munching on dead trees seasonally or during times when other food sources weren’t available. Another hypothesis is that these "ancient fecal producers," as the researchers call them, might have eaten the rotting wood, with its calcium-rich crustaceans and protein-laden invertebrates, during egg production, similar to the feeding patterns of modern birds during breeding season.

Regardless of the reason, these findings could change how we think about what big dinosaurs ate.

[h/t Nature News]

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