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10 Bone-Headed Facts About Pachycephalosaurus

Pachycephalosaurus’ domed, heavily-built head looks like it was capable inflicting some serious damage. Unfortunately, trying to decipher how this animal used that noggin has given many poor scientists headaches of their own.

1. Its Skull Roof was Up to 10 Inches Thick.

Pachycephalosaurus heads only reached total lengths of two feet or so. In case you’re curious, human men and women have an average skull thickness of 6.5 and 7.1 millimeters, respectively.

2. Pachycephalosaurus Heads Were Once Mistaken for Dinosaur Kneecaps.

Dinosaurs—unlike mammals—lacked kneecaps altogether. However, during the late 19th century, this fact wasn’t widely known, and few non-skull-related Pachycephalosaurus bones had been found, so this weird hypothesis is pretty forgivable.

3. One of its Close Cousins Has the World’s Longest Dinosaur Name.

Try saying this five times fast: Micropachycephalosaurus. It means “small, thick-headed lizard.” What a flattering label!

4. Pachycephalosaurus May Have Drastically Changed Shape with Age.

Dr. John R. “Jack” Horner—who, among other accomplishments, served as the Jurassic Park trilogy’s dino consultant—maintains that Pachycephalosaurus and two similar creatures which shared its habitat were really the same animal. Stygimoloch and Dracorex are smaller and had much flatter skulls. If Horner’s correct, these represent two juvenile stages of Pachycephalosaurus. He expands upon his argument at the 8:30-mark of this TED clip: 

5. It Belongs to the Same Dinosaur Clade as Triceratops.

Triceratops and its horned/frilled kin are collectively known as “ceratopsians.” Together with the pachycephalosaurids, they form a diverse dinosaurian group called the marginocephalia (“ridged heads”).

6. Perhaps Pachycephalosaurus Butted Heads.

Paleo-artists have traditionally drawn Pachycephalosaurus ramming headlong into each other musk ox-style. Does the available evidence support this?  Some scientists think so, claiming that their domes were well-equipped for absorbing such brutal impacts. Others, meanwhile, have their doubts.

7. … Or, Alternatively, Pachycephalosaurus Might’ve Preferred Flanking.

Today’s giraffes violently slam their heads into rivals’ sides. Maybe Pachycephalosaurus behaved likewise. Many of its kin had conspicuously-wide ribcages, which could theoretically withstand this sort of abuse. Also, try making two bowling balls forcefully collide at point-blank range. You’ll notice that the spheres will only briefly connect before quickly sliding apart thanks to their curvature. Pachycephalosaurus domes were also quite rounded and potentially faced the same mechanical challenge. If so, “flanking” might’ve been a more effective undertaking when tempers flared.

8. Pachycephalosaurus Had to Worry About T. rex.

Tyrannosaurus and Pachycephalosaurus both dwelled in western North America during the late Cretaceous period around 65 million years ago. That thick head was therefore possibly employed as an anti-predator weapon. 

9. Regardless, Pachycephalosaurus Could Sustain some Serious Cranial Trauma.

In 2012, paleontologist Joseph Peterson subjected a Pachycephalosaurus skull to CT scanning and found numerous potential injury marks “clustered over the thickest region of the dome,” which—in his view—seemingly corresponded with the head-butting hypothesis.

10. Pachycephalosaurus is (Indirectly) Linked to the Harry Potter Series.

To honor its dragon-like appearance and a certain best-selling book series, one new pachycephalosaurid species was named Dracorex hogwartsia in 2006. Upon hearing the good news, J.K. Rowling proclaimed “[this] is easily the most unexpected honor to have come my way since the publishing of the Harry Potter books! I am absolutely thrilled to think that Hogwarts has made a small claw mark on the fascinating world of dinosaurs.” She also added that “I can’t help but visualizing [Dracorex] as a slightly less pyromaniac Hungarian Horntail.”

But don’t get too excited, Potter fans. Remember: Dracorex could simply be nothing more than a young Pachycephalosaurus, which would make the Hogwarts-themed moniker obsolete. 

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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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