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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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Prehistoric Ticks Once Drank Dinosaur Blood, Fossil Evidence Shows
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Ticks plagued the dinosaurs, too, as evidenced by a 99-million-year old parasite preserved inside a hunk of ancient amber. Entomologists who examined the Cretaceous period fossil noticed that the tiny arachnid was latched to a dinosaur feather—the first evidence that the bloodsuckers dined on dinos, according to The New York Times. These findings were recently published in the journal Nature Communications.

Ticks are one of the most common blood-feeding parasites. But experts didn’t know what they ate in prehistoric times, as parasites and their hosts are rarely found together in the fossil record. Scientists assumed they chowed down on early amphibians, reptiles, and mammals, according to NPR. They didn’t have hard evidence until study co-author David Grimaldi, an entomologist at the American Museum of History, and his colleagues spotted the tick while perusing a private collection of Myanmar amber.

A 99-million-year-old tick encased in amber, grasping a dinosaur feather.
Cornupalpatum burmanicum hard tick entangled in a feather. a Photograph of the Burmese amber piece (Bu JZC-F18) showing a semicomplete pennaceous feather. Scale bar, 5 mm. b Detail of the nymphal tick in dorsal view and barbs (inset in a). Scale bar, 1 mm. c Detail of the tick’s capitulum (mouthparts), showing palpi and hypostome with teeth (arrow). Scale bar, 0.1 mm. d Detail of a barb. Scale bar, 0.2 mm. e Drawing of the tick in dorsal view indicating the point of entanglement. Scale bar, 0.2 mm. f Detached barbule pennulum showing hooklets on one of its sides (arrow in a indicates its location but in the opposite side of the amber piece). Scale bar, 0.2 mm
Peñalver et al., Nature Communications

The tick is a nymph, meaning it was in the second stage of its short three-stage life cycle when it died. The dinosaur it fed on was a “nanoraptor,” or a tiny dino that was roughly the size of a hummingbird, Grimaldi told The Times. These creatures lived in tree nests, and sometimes met a sticky end after tumbling from their perches into hunks of gooey resin. But just because the nanoraptor lived in a nest didn’t mean it was a bird: Molecular dating pinpointed the specimen as being at least 25 million years older than modern-day avians.

In addition to ticks, dinosaurs likely also had to deal with another nest pest: skin beetles. Grimaldi’s team located several additional preserved ticks, and two were covered in the insect’s fine hairs. Skin beetles—which are still around today—are scavengers that live in aerial bird homes and consume molted feathers.

“These findings shed light on early tick evolution and ecology, and provide insights into the parasitic relationship between ticks and ancient relatives of birds, which persists today for modern birds,” researchers concluded in a news release.

[h/t The New York Times]

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The Clever Adaptations That Helped Some Animals Become Gigantic
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Imagine a world in which eagle-sized dragonflies buzzed through the air and millipedes as long as kayaks scuttled across Earth. "Ick"-factor aside for bug haters, these creatures aren't the product of a Michael Crichton fever dream. In fact, they actually existed around 300 million years ago, as MinuteEarth host Kate Yoshida explains.

How did the prehistoric ancestors of today’s itty-bitty insects get so huge? Oxygen, and lots of it. Bugs "breathe by sponging up air through their exoskeletons, and the available oxygen can only diffuse so far before getting used up," Yoshida explains. And when an atmospheric spike in the colorless gas occurred, this allowed the critters' bodies to expand to unprecedented dimensions and weights.

But that's just one of the clever adaptations that allowed some creatures to grow enormous. Learn more about these adaptations—including the ingenious evolutionary development that helped the biggest dinosaurs to haul their cumbersome bodies around, and the pair of features that boosted blue whales to triple their size, becoming the largest animals ever on Earth—by watching MinuteEarth's video below.

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