May 3, 2012
Did dome-headed dinosaurs really butt heads? While not one of the most important subjects in paleontology, the question is one of the most fraught. The thick-skulled dinosaurs look as if they were perfectly suited to cracking heads, much like modern bighorn sheep do, but whether or not dinosaurs like Pachycephalosaurus really knocked noggins has depended on who you asked. While some studies have concluded that these dinosaurs were fully capable of bashing skulls, other analyses have disagreed and pointed out that rounded, dome-shaped heads were actually poor weapons in such contests.
The evidence from bone histology and the estimated defensive capabilities of pachycephalosaurs is ambiguous. But a conspicuous lack of skull pathologies seemed to support the idea that these dinosaurs were not butting heads, but instead rammed each other in the flanks or used their domes primarily as flashy ornaments. If pachycephalosaurs were regularly crashing headlong into one another, we would expect many of their skulls to show impact damage from such encounters.
For many years, no one had recorded the expected injuries. That changed this week thanks to a new PLoS One paper by Joseph Peterson and Christopher Vittore. The subject of their paper, titled “Cranial pathologies in a specimen of Pachycephalosaurus,” is a damaged portion of skull from the largest and most famous of all the dome-headed dinosaurs.
The dinosaur’s skull looks as if someone went at it with a hammer. Two large depressions—augmented by numerous smaller pits inside and along their margins—pock the top of the dome. Peterson and Vittore considered several possibilities, including damage caused to the bone after the animal’s death, bone resorption and trauma incurred during the dinosaur’s life. Injury followed by infection seems to be the explanation most consistent with the evidence. And this may not be the only skull of its kind. Towards the end of the paper, Peterson and Vittore point out that a skull of the pachycephalosaur Gravitholus and another belonging to Texacephale appear to have similar injuries to the top surfaces of their skulls.
Case closed, right? This would seem to be pretty good evidence that Pachycephalosaurus really did butt heads. But we should take care in how far we extend hypotheses from one skull. The injuries on the Pachycephalosaurus skull accord with the idea that these dinosaurs were butting heads, but we can’t actually know what happened to this particular dinosaur. The case for head-butting dinosaurs just got a boost, but it would be premature to say whether pachycephalosaurs definitely did or did not engage in the behavior on a regular basis. If the dinosaurs commonly crashed craniums, other damaged domes should be out there. There may be some waiting in the rock or sitting on museum shelves. One thing seems certain, though—Peterson and Vittore’s dinosaur probably had one hell of a headache.
For more on this research, see David Orr’s post at Love in the Time of Chasmosaurs.
Peterson, J., & Vittore, C. (2012). Cranial Pathologies in a Specimen of Pachycephalosaurus PLoS ONE, 7 (4) DOI: 10.1371/journal.pone.0036227
March 17, 2011
During the latter half of the 1980s, when I was just becoming acquainted with dinosaurs, “Brontosaurus” was just on its way out. A few of my books depicted the lumbering dinosaur, and a few museums still had the wrong heads on their skeletons, but the images of slow, stupid Brontosaurus were slowly being replaced by Apatosaurus. By the time the U.S. Postal Service issued a Brontosaurus postage stamp in 1989, dinosaur fans were quick to point out that the animal was called Apatosaurus and that the old name had been tossed in the taxonomic dustbin.
Paleontologist Elmer Riggs recognized that Brontosaurus and Apatosaurus were one in the same in 1903, and most paleontologists quickly agreed that he was correct. So why did Brontosaurus hang around for another 80 years? As Paul Brinkman noted in his retelling of the events, museums like the American Museum of Natural History in New York City, the Carnegie Museum of Natural History in Pittsburgh and even the Field Museum in Chicago—Riggs’ academic home—kept using the name Brontosaurus for their skeletons. It was not until 1979, when the correct skull of Apatosaurus was finally found, that the title Apatosaurus began to gain some popularity. Paleontologists may have abandoned Brontosaurus by the early 20th century, but it lived on in the public imagination, and this dinosaur remains a fan favorite.
After asking “Were you inspired by a dinosaur?” earlier this week, my friend Scicurious responded that Brontosaurus sparked her interest in science, although she was disheartened to learn that her different Brontosaurus and Apatosaurus models actually represented the same dinosaur:
So you can imagine my horror when I found out that [the dinosaur] was not a brontosaurus. It was an apatosaurus. I think it was some older know-it-all kid who told me. I didn’t believe it. I read they were the same and I STILL didn’t believe it. People were lying to me. Everyone knew brontosaurus and apatosaurus weren’t the same!!! My model of brontosaurus had a smooth chin. Apatosaurus had a floppy chin like a turkey and some sort of fleshy crest. TOTALLY DIFFERENT (my 7 year old mind probably never figured on the improbability of a floppy chin getting fossilized). Besides, brontosaurus was awesome!!! Apatosaurus was for losers. Brontosaurus sounds better, right? Right??!
It’s hard to compete with the evocative name and famous image of Brontosaurus, and others agreed. When Scicurious and I started talking about the “thunder lizard” on Twitter, Ed Yong cast his vote for Brontosaurus, adding the hashtag #alwaysBrontosaurustome. Maria Wolters responded with “Is it wrong that I hear Billy Joel singing that hash tag?” (referring to his hit “She’s Always a Woman“), which inspired Scicurious to write an impromptu ode to everyone’s favorite, long-lost dinosaur:
“Always Brontosaurus to me”
You were my favorite sauropod
my vegetarian with heavy plod
and then I found out something odd
you disappeared and I am left aloooooone…
Who’s this apatosaurus guy?
he’s got those same thunder thighs
and that long neck that reached the skyyyy
but he’s not YOUUUUUU….
For you’re always Brontosaurus to meeee
the greatest dino that there will ever beee
You’re the only Sauropod that I neeeeeeed
brontosaurus, always Bronty to meeeee
Zen Faulkes, who also responded to my question with a post of his own about dinosaur model kits, also contributed his own ditty “Bronto is Everywhere,” though I’m not so sure that Brontosaurus had a role in creating Stonehenge.
Part of me wishes that Brontosaurus was a real dinosaur and not a synonym for Apatosaurus. Even if the plodding creature with the Camarasaurus-like head I grew up with never existed, Brontosaurus is such a fantastic name that it seems a shame not to use it. (Brontomerus, “thunder thighs,” is wonderful, too, but this Utah sauropod can’t replace my memories of Brontosaurus.)
According to some paleontologists, there is a slim chance Brontosaurus will make a return someday. Robert Bakker and others have argued that the skeleton originally called Brontosaurus—known as Apatosaurus excelsus today—is distinct enough from the bones of the dinosaur Apatosaurus ajax to merit its own genus. The majority of paleontologists continue to use Apatosaurus for both species—they are very similar to each other—but there remains a sliver of a possibility that future, in-depth research might bring Brontosaurus back. For now, the science is still on the side of Apatosaurus, but imagine the celebration if Brontosaurus returned to us.
BRINKMAN, P. (2006). Bully for Apatosaurus Endeavour, 30 (4), 126-130 DOI: 10.1016/j.endeavour.2006.10.004
December 9, 2010
I have never been particularly good at sending out Christmas cards. By the time I get into the holiday spirit and remember, it is usually December 24th. This year, however, the Etsy member FrankNBones has given me a good excuse to do things right with a unique set of dinosaur holiday cards!
Featuring the dinosaur celebrities Tyrannosaurus, Triceratops, Velociraptor, Brachiosaurus, Dilophosaurus and Parasaurolophus, each card depicts a dinosaur skull with a holiday flourish. (I especially like the Dilophosaurus skull with the jingle bells.) Each one is unique. As their creator explains on the store page:
These original, hand-pulled linocut carvings are printed on 5×7 inch cards. The linoleum blocks were cut by hand, inked, and printed individually. Due to the printing process, there are variations and imperfections from print to print, and no two cards are the same.
Now all I have to do is figure out what to write inside them. (“RAWR”?)
November 8, 2010
The rise and fall of “Brontosaurus” is one of my most favorite stories in all of paleontology. Fossil discoveries, academic arguments, evolutionary scenarios, museum politics and public perception all played into the long-running debate about a dinosaur that only ever existed in our imagination, yet it still remains such a popular name that almost every book or museum display about Apatosaurus is obligated to include a “Previously known as Brontosaurus” clause. You can imagine my delight, then, when I visited Yale’s Peabody Museum of Natural History and spotted the original head of their Brontosaurus.
By the time the Yale skull was created, the debate over the skull shape of Brontosaurus had already been going on for several decades: There was an inkling that some of the long, low skulls attributed to Diplodocus from Utah’s Dinosaur National Monument really belonged to Brontosaurus, but many restorations presented the animal with a shorter, boxy skull like that of Camarasaurus. O.C. Marsh, the famous 19th-century paleontologist and founder of the Peabody Museum, had been the architect of the latter interpretation, basing his illustrations of the dinosaur’s head on skull materials that were later found to belong to Camarasaurus and Brachiosaurus.
Marsh was not very well-liked by the crop of paleontologists that followed him – what better way to secure your own place as a leading paleontologist than to show that Marsh was wrong? – but in this case many other authorities followed his lead. For the Yale reconstruction, the preparator based the skull shape off of a bit of lower jaw from Wyoming designated YPM 1911, which appeared to confirm that Brontosaurus had a Camarasaurus-like head. The end result, mostly created out of plaster, was a squared-off head with protruding jaws and a nasal opening that pushed up the skull to give the dinosaur a rather snooty air. Completed in the 1920s, this reconstruction was mounted on the museum’s mighty sauropod in 1931 and was key reference the artist Rudolph Zallinger used in creating the great “Age of Reptiles” mural that still provides the backdrop to the museum’s dinosaur hall.
As museums revamp their exhibition space, the image of dinosaurs I grew up with is slowly being replaced. This is a good thing, but I also cherish the fact that paleontologists are aware of their own history. Our science does not proceed simply by collecting new evidence. Paleontologists must also reexamine old ideas and previously-discovered fossils to glean new insights, and I am glad to see that history often has a prominent place in many fossil halls. The stupid, swamp-bound Brontosaurus I was introduced to as a child never existed, but we can still learn something by reminding ourselves how and why that imagery was replaced.
November 5, 2010
Sauropods were exceptionally strange creatures. With tiny heads mounted at the tip of ludicrously long necks anchored on a massive body with tapering tails on the other end, they were truly marvels of evolution. As odd as the basic sauropod body plan was, though, many sauropods had armor, clubs, sails and other features which only added to their unique character. Among them was Bonitasaura, a roughly 83-million-year-old “beaked” sauropod from Argentina.
Bonitasaura was originally described in 2004, but now paleontologists Pablo Gallina and Sebastián Apesteguía have redescribed its skull with more recently discovered fragments in a report to be published at Acta Palaeontologica Polonica. This peculiar dinosaur was a member of the widespread group of Cretaceous sauropods called titanosaurs, and these sauropods proliferated in South America and elsewhere during a time when North America was devoid of the classic sauropod communities that had thrived during the Late Jurassic. Despite what scientists have learned about titanosaurs in the past few decades, however, we still know relatively little about their skulls. As with sauropods in general, titanosaur skulls are seldom found, and the discovery of skull material from Bonitasaura offers a rare perspective on the diversity of head shapes among these giants.
Gallina and Apesteguía did not have a complete, articulated skull to work with. Instead only bits and pieces of the skull were found, each part of an osteological puzzle that was this animal’s head. When put all together, though, the general shape of the skull could be ascertained, and the paleontologists found that Bonitasaura had a skull that was short from front to back, with a squared muzzle that flared out to the sides. (Superficially, the skull vaguely resembled that of Nigersaurus, a distantly related sauropod cousin with a head like a Hoover vacuum. While the authors do not mention Nigersaurus specifically, they note that this jaw type now appears to have evolved independently in different groups of sauropods.) Furthermore, as pointed out in the original description, this dinosaur did not have a beak like a parrot or hadrosaur, but instead possessed a sheath of keratin on its jaws behind its teeth, which may have created a sharp cutting edge for processing plant food.
The skull shape of Bonitasaura differs from the long and low skulls of other titanosaurs, and the new characteristics seen among elements prepared since the dinosaur’s initial description has allowed it to be grouped with other titanosaurs such as Mendozasaurus, Antarctosaurus and—what surely must be a top contender for the more tongue-twisting dinosaur name—Futalognkosaurus. Frustratingly, the precise relationships of these sauropods are still blurry, and hopefully future discoveries will bring resolution to the sauropod family tree.
Pablo A. Gallina and Sebastián Apesteguía (2010). Cranial anatomy and phylogenetic position of the titanosaurian sauropod Bonitasaura salgadoi Acta Palaeontologica Polonica (in press)
Apestegu�a, S. (2004). Bonitasaura salgadoi gen. et sp. nov.: a beaked sauropod from the Late Cretaceous of Patagonia Naturwissenschaften, 91 (10), 493-497 DOI: 10.1007/s00114-004-0560-6