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10 Mousey Facts About Mussaurus

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Scientists know little about what growing up in the age of dinosaurs was like, but Mussaurus can help us better explore this intriguing subject. 

1. Its Name Means “Mouse Lizard.”

Was Mussaurus especially rodent-like? No, but babies measuring under 8 inches long have been unearthed, hence the cute-sounding genus name.  

2. It Gets a Cameo in Michael Crichton’s The Lost World.

Early on, one of the novel’s protagonists gingerly picks up a palm-sized Mussaurus. However, for reasons unknown, Spielberg cut this little herbivore from The Lost World: Jurassic Park, his 1997 film adaptation.

3. Mussaurus is Often Mistaken for a Dinosaur Record-Holder.

Mussaurus was originally discovered in 1979 and, at the time, was known only from hatchling remains. Ever since, popular science books have been touting it as the “world’s smallest known dinosaur.” But don’t call Guinness just yet! Paleontologists estimate that average adults would have been over 10 feet long, making Mussaurus far too large to merit this distinction—an assessment vindicated two years ago, when a quartet of grown-up specimens emerged.

Today, the tiniest living dino is the bee hummingbird (Mellisuga helenae), which can comfortably perch on the end of a pencil. But what about those non-avian, extinct varieties? China’s 16-inch Anchiornis huxlei (pictured above) currently takes the cake.

4. Creepy-Crawlies Might Have Been on its Menu.

Paleo-artist Gregory S. Paul believes that, given the shape of their teeth, “small juvenile Mussaurus ... supplemented their diet with insects.” Hey, arthropods are a great source of protein—don’t knock ‘em ‘til you’ve tried ‘em!

5. The Oldest-Known Dinosaur Nest Likely Belonged to a Mussaurus.

In Patagonia’s bountiful fossil beds, seven juveniles were spotted hanging out together next to a pair of decently-preserved eggs. If this actually represents a dinosaurian nesting site, at 215 million years old, it would be the earliest we’ve yet discovered.

6. It Preferred Walking on All Fours.

Mussaurus hatchlings had some relatively long bones in their forelimbs, so the wee beasties most likely got around quadrupedally.     

7. Mussaurus Was Originally Misidentified as a Different Dino.

Remember those mature Mussaurus we brought up earlier? Despite the fact that they lived in Argentina, paleontologists once mistook them for Plateosaurus, a long-necked, stiff-tailed genus known exclusively from Europe (though, in all fairness, those two continents were connected back then as parts of a huge landmass called “Pangaea”).

8. It Had “Extremely Thin” Eggshells.

“You’re a tough egg to crack” … or are you? Mussaurus eggs are notable for having unusually thin shells, compared to most sauropodomorphs (“long-necked” dinos), whose babies had to fight through much thicker casings. Maybe their descendants evolved heftier eggshells as a defense against omelette-savoring predators.

9. Mussaurus Parents Probably Stuck Around.

To many animals, getting abandoned by dads and moms is considered normal. But the fact that partially-grown juvenile Mussaurus have been found near egg fragments might imply some level of parental care. In all probability, the little bundles of joy would have needed it—babies had awkward proportions and were likely rather helpless.

10. Mussaurus Heads Would Have Changed a Lot with Age.

There’s a reason the DMV doesn’t let you use a baby photo on your driver’s license. As people grow, their appearance changes dramatically, and dinosaurs were no different. Relatively speaking, newly-hatched Mussaurus had bigger eyes, shorter snouts, and larger nasal bones than older individuals.

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The T. Rex Fossil That Caused a Scientific Controversy
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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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