Get Fuzzy on the Extinction of the Dinosaurs

Last Monday's 'Get Fuzzy' strip featuring Satchel the dog and Bucky the cat. By Darby Conley

What killed off the non-avian dinosaurs? Over the years climate change, mammals with a taste for dinosaur eggs, the laziness of dinosaurs, and even hungry, hungry caterpillars have been blamed, with the current favored culprit being an asteroid that struck in the vicinity of today’s Yucatan peninsula about 65 million years ago. But Bucky the cat from the comic strip Get Fuzzy isn’t convinced that scientists are any closer to solving the mystery.

In a string of strips that started on September 20, Bucky goes off on a tear about science when Satchel tells him that dinosaurs were killed by “a rare kind of flying rock” (which Bucky misinterprets as a “space hemorrhoid”). From there Bucky’s idle speculations begin to spin a little out of control—I won’t spoil it for you; go read the strips—but I think Bucky’s wild ideas underscore an important lesson. While it was controversial three decades ago, today we take the idea that the end-Cretaceous extinction was caused by an asteroid for granted. Many books and documentaries refer to it, but relatively little detail is ever given about the ecological crisis it caused or how the impact could have killed so many forms of life. (And, of course, there are still some who argue that the impact would have been insufficient and that intense volcanic eruptions or some other cause triggered the extinction.) If we really want to inform the public about science, just saying a flying rock did it doesn’t cut it.

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Stegosaurus Week: The Weak Bite of Stegosaurus

An Allosaurus menaces a Stegosaurus and its offspring. Image from Wikipedia.

In discussions of dinosaur bite mechanics, the heavy forces generated by predatory species often dominate, but it is important to understand how the jaws of herbivores worked, too. The jaws of Stegosaurus might not be as immediately impressive as those of Tyrannosaurus rex, but it is still important to know how they were put to use if we are to understand the paleobiology of the famous armored dinosaur. Now, thanks to computer models created by Miriam Reichel, we can better understand what Stegosaurus was capable of eating.

The teeth of Stegosaurus are almost all the same: a series of rounded, minutely-ridged teeth arranged in straight rows from front to back. To investigate how this dental arrangement would have worked while consuming food, Reichel created 3-D models of the teeth (both with ridges and without) to create a virtual model of Stegosaurus jaws. This digital dinosaur was then set to work on computer-generated cylinders given the properties of different types of plant food, using the muscle attachments seen on the dinosaur’s skull to determine how hard its bite would have been.

As calculated by Reichel, Stegosaurus didn’t have a very powerful bite. Even you and I could bite harder than Stegosaurus. The dinosaur could generate enough force to crunch through twigs and branches under a half an inch in diameter, but anything bigger than that and it would have a difficult time of it. Given its weak jaws, Stegosaurus would have had to rely on soft, fast-growing plants; it is fantastic to think that this large dinosaur could have survived on such a diet!

Then there is the matter of the actual method by which Stegosaurus processed its food. It probably did not chew its food to any great degree, but instead sliced through soft plants before swallowing. Additionally, Reichel proposes that Stegosaurus may have had a tough beak at the front of its jaws which took most of the punishment during feeding. The teeth were left with the lighter work, although, since Stegosaurus jaws were weakest at the front, this might mean that it was only eating the softest, greenest food available. Further study will be required to understand the precise mechanics of how Stegosaurus ate, but, at the very least, Reichel’s work confirms that this dinosaur had to carefully pick out soft Jurassic salads for lunch.

Reichel, M. (2010). A model for the bite mechanics in the herbivorous dinosaur Stegosaurus (Ornithischia, Stegosauridae) Swiss Journal of Geosciences DOI: 10.1007/s00015-010-0025-1

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New Horned Dinosaurs From America’s Lost Continent

Skeletal restorations of Utahceratops (left) and Kosmoceratops (right). The yellow bones are those that have been recovered for each species. From Sampson et al., 2010.

At the height of the golden era of dinosaur science, it takes something special for a newly described dinosaur species to stand out. Dinosaurs with dual sickle claws, humps,  or unexpected bristles more readily grab the attention of the public than more familiar-looking forms, but looks aren’t everything. A pair of horned dinosaurs described today in PLoS One are noteworthy for reasons that go beyond their strange appearances.

A few months ago, I was fortunate enough to visit the Utah Museum of Natural History’s paleontology field crew at their camp in southern Utah’s Grand Staircase-Escalante National Monument. The arid, rocky landscape was rich in dinosaur fossils, but 75 million years ago this same place would have looked very different. During that time in earth’s history, near the close of the Cretaceous, a shallow sea over the center of North America divided the landmass into two separate continents: Appalachia to the east and Laramidia to the west. The area which is today Grand Staircase-Escalante National Monument was in the middle of the thin western continent, and according to Scott Sampson, University of Utah paleontologist and lead author of the new paper, the place was “a wet, swampy setting akin to present-day northern Louisiana.” Crocodiles, turtles, and at least 16 unique species of dinosaurs thrived here, including the two horned dinosaurs announced today.

Named Utahceratops gettyi and Kosmoceratops richardsoni, respectively, the two dinosaurs belonged to a subdivision of the horned dinosaur family called chasmosaurines. Roughly speaking, this group of horned dinosaurs can often be identified by their large brow horns and their wide, squared-off frills, and both Utahceratops and Kosmoceratops fit the classic chasmosaurine type. Nevertheless, both were distinct from species previously recognized and were significantly different from each other. While Utahceratops had relatively short brow horns in front of a large frill that was slightly indented inwards along its top margin, the slightly smaller Kosmoceratops had longer brown horns and an array of spikes that spilled forwards over its frill like a chasmosaurine comb-over.

In contrast to more familiar chasmosaurines like Triceratops, though, the browhorns in both Utahceratops and Kosmoceratops were oriented out to the side rather than forward. Why this should be so is unclear. Co-author Andrew Farke of the Raymond M. Alf Museum of Paleontology says, “it’s hard to know for sure, but in modern horned animals horn orientation usually relates to horn function.” Perhaps Utahceratops and Kosmoceratops had similar styles of combat with members of their own species, Farke hypothesizes, or maybe the peculiarity was inherited in both from a common ancestor. Likewise, according to Sampson, the sideways orientation of these horns is also seen in another horned dinosaur from Coahuila, Mexico, and may be a common characteristic of chasmosaurines from this part of Laramidia. Among these dinosaurs, “the sideways-oriented horns offer another means to lock heads and engage in contests of dominance,” Sampson says; “they would also have made effective visual signals, particularly in Kosmoceratops.”

Utahceratops and Kosmoceratops were also very different from the horned dinosaurs that lived in the same area a few million years earlier. While both of the new dinosaurs came from the Kaiparowits Formation, horned dinosaurs of a different sort have been found in the national monument’s 80-million-year-old Wahweap Formation. These older dinosaurs, such as the many-horned Diabloceratops, belonged to another branch of the horned dinosaur family tree called the centrosaurines. “If you were to line up the skulls [of the Wahweap and Kaiparowits dinosaurs] side by side,” Farke says, “they would look strikingly different!” especially since the two newly described dinosaurs had relatively larger and more ornamented frills.

Given the degree of completeness of both dinosaurs (entire skulls for both, the majority of the skeleton of Utahceratops, and the skeleton except the tail, feet, and forelimbs in Kosmoceratops), their description is a major contribution to our understanding of ceratopsid anatomy and diversity. What makes them especially noteworthy, however, is that they confirm the existence of disparate pockets of dinosaur evolution along the western continent of Laramidia. These genera were not evenly spread from Mexico to Canada, but were distinct from the horned dinosaurs that lived at the same time in the northern part of the continent. This is not just an accident of sampling, the authors of the new study propose, but a signal of a real biogeographical phenomenon.

The picture that emerges from the distribution of the horned dinosaurs around 75 million years ago is that there were at least two separate centers of chasmosaurine evolution on the western continent. Where there were Chasmosaurus, the recently-described Mojoceratops and Vagaceratops (previously Chasmosaurus irvinensis, but renamed by the authors of this study) to the north, Utahceratops, Kosmoceratops and Pentaceratops lived in the far south. Based on the distribution of these dinosaurs in space and time, Sampson, Farke and their colleagues propose that about 77 million years ago there was a barrier that separated chasmosaurines in the north from those in the south. This barrier would have precipitated the divergent evolution of the northern and southern groups identified in the study, though the close relationship of Kosmoceratops and Vagaceratops found by the scientists suggests that these dinosaurs shared a close common ancestor that spread after this impediment was removed about 75.7 million years ago. As Sampson states by e-mail, the recognition of this patten raises some important questions about dinosaur evolution on Laramidia:

The implications of this finding huge, given that Laramidia was a landmass about one-third the size of present day North America, and much of this area was likely off limits to large dinosaurs because of large mountain ranges to the west.  Today we have a handful of rhino-to-elephant sized mammals living on Africa.  At present, it seems that there were at least 15-20 rhino-to-elephant sized animals living on Laramidia 76 million years ago, despite the fact that it was less than one-fifth the size of Africa.  How did so many species of giants co-exist on such a small chunk of land?  The answer may relate to available fodder (more biomass than at present) and/or to metabolic rates (slower in dinosaurs than in mammals).  Either way, these finding suggest that the hothouse world of dinosaurs was, at least in some respects, very different than the one we know today.

Furthermore, if the pattern of evolution in these horned dinosaurs really was influenced by the existence of an ancient barrier, then the same signs of isolation should be seen among other dinosaurs, as well. Hadrosaurs and tyrannosaurs probably would have been isolated in the same way, and the discovery and description of additional dinosaurs from Grand Staircase-Escalante National Monument will be pivotal in further tests of this idea. Determining just what the barrier might have been, though, is another mystery. At present there is no sign of an actual physical barrier, though the authors of the new study suggest a previously-unidentified mountain range, temporary flooding by the nearby sea, a turbulent river system, or some kind of ecological barrier as possibilities.

The story of Laramidia will not be resolved by one paper alone, but will take years of study by many paleontologists. This is a good thing. Through something as simple as the description of two dinosaurs, paleontologists have placed the fauna of an entire lost continent in a new context, and, armed with a new set of questions, paleontologists can return to the strata of southern Utah in search of answers.

References:

Sampson, S., Loewen, M., Farke, A., Roberts, E., Forster, C., Smith, J., & Titus, A. (2010). New Horned Dinosaurs from Utah Provide Evidence for Intracontinental Dinosaur Endemism PLoS ONE, 5 (9) DOI: 10.1371/journal.pone.0012292

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Dinosaur Drive-In: When Dinosaurs Ruled the Earth

If paleontologists have said it once, they have said it a hundred times: non-avian dinosaurs and humans never coexisted. Most people who insist otherwise are creationist cranks who believe that evidence of a living dinosaur would somehow undermine evolutionary theory, but I understand that Hollywood has to play by different rules. Dinosaurs are just not as exciting without people to menace, and so it has been traditional to use time travel, the existence of prehistoric “lost worlds,” fertilized eggs preserved for over 65 million years and genetic engineering experiments gone awry to bring dinosaurs and people together. But none of these options worked for the creators of the 1970 Hammer film When Dinosaurs Ruled the Earth. They wanted dinosaurs and other prehistoric monsters to attack scantily-clad cavepeople, and so they made a film that a biblical fundamentalist could take as a documentary rather than fiction.

When Dinosaurs Ruled the Earth doesn’t begin with a shot of a steaming, primeval forest, but of a gaggle of tanned and oiled cavepeople who have crawled out of their cliffside dwellings to engage in their regular “let’s pick which blond woman we want to sacrifice” ritual. Naturally, the prospective victims are not very happy about this—one throws herself off a cliff—but when they try to escape they are hindered by the fact that they are wearing prehistoric underwear so skimpy that it actually makes it more difficult for them to run away. It would have made more sense for them to lose the push-up bras and just bolt for it, though I imagine going streaking during prehistory would have presented its own unique risks.

In any event, one of the Cenozoic supermodels—named Sanna—does manage to escape by jumping into the sea and is promptly rescued by a conveniently placed group of fishermen whose unfortunate garments remind us why it’s never wise to wear thongs in a windstorm (I wish I were talking about sandals here—yikes). It is among this group of unfortunately attired men that we meet Tara, our film’s scruffy male lead. Meanwhile, back at the ranch, the musclebound leader of the cavepeople is clearly upset that the sacrifice did not go as planned; he shouts incomprehensible phrases and gestures widely to get people to go do whatever it is they do. Maybe this was intended as a bit of fun for the audience—make up your own dialogue as you go along—especially since words like “akita” appear to mean: “Over there”; “Stop”; “Give me that”; “Come over here” and “Let’s have pancakes for dinner tonight.”

For me, though, the film’s real stars are the prehistoric creatures that help to thin out the cast, and the audience’s first look at one of the film’s exquisite stop-motion monsters comes when the fishermen return with the woman to their camp. While the dudes were out fishing, someone brought a plesiosaur (which is, of course, not a dinosaur) to the big clam bake, but damned if they knew what to do with the thing. It was too angry to just stick an apple in its mouth and start slow-roasting it, and when half the village runs over to examine their new visitor their dinner tries to make a break for it. Unfortunately, though, the plesiosaur wanders right into a mess of fluid the tribe uses for lighting fires, and soon the only question on anyone’s mind is: “White meat or dark?”

Things don’t look so rosy the next day. The cliffdwellers are still miffed that their sacrifice just up and left, and Tara’s wife isn’t too happy that he came back with a new, blond girlfriend. When Sanna’s captors show up, she makes a break for it, and thanks to an assist from an angry Chasmosaurus she gets a little extra time to get away. That does little to help the fisherman and his friends, though—when they set out after her the same dinosaur causes them a spot of trouble before throwing itself into what sounds like a bottomless pit (lots of roaring, but no crash). Sanna also encounters some of the dangerous local fauna when she finds herself being enveloped by a carnivorous plant, although I would not recommend her escape technique of reaching outside to stab inwards at the plant’s tough outer hide (pointsy towardsies = bad).

The remainder of the film is little more than an excuse to watch Victoria Vetri run around in an embarrassingly small bikini. Thankfully, there are a few more prehistoric critters to help break the movie’s naked tedium. A newly-hatched baby something-o-saurus and its mother (which look like cousins of the Beast from 20,000 Fathoms) provide a brief bit of comic relief as they try to figure out whether Sanna is friend or food; an attack by an oversized Rhamphorhynchus livens things up a bit, and when Tara returns home to find that his tribe doesn’t think it’s cool that he ran off with someone else’s sacrifice, they try to serve him up on a raft to the local Tylosaurus. (The marine reptile responds by tossing him off the raft. “Yecch! Human? No thanks – I’m trying to cut back on junk food.”) Given how good these stop-motion creatures look, though, it is sad that the film also resorts to gluing plates and spikes on alligators and monitor lizards and making them fight, a practice that is despicable as it is lazy.

In the end, a giant tidal wave wipes away the coastal village but delivers our heroes to a mountaintop to observe a lunar eclipse. Dumb, but attractive, they would go on to found a settlement along the southern coast of California which would eventually be named Los Angeles. What happened to all the prehistoric monsters is unclear, though. Perhaps they got so tired of the cavepeople’s shenanigans that they eventually died of boredom—a risk I certainly felt while watching this vintage 1970s schlock.

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Stegosaurus Week: Tracking Cryptic Stegosaurs

The partial skeleton of Dacentrurus described by Richard Owen. From Wikipedia.

The first trace of the plated, spiky stegosaurian dinosaurs was found in Early Cretaceous rock near Grahamstown, South Africa. Uncovered by W. G. Atherstone and A. G. Bain in 1845, the dinosaur was represented by a partial skull and several limb bones. The naturalists felt unqualified to study them and sent the fossils to Richard Owen in England. When Owen eventually got around to describing them, he confused parts of the stegosaur with bones from armored reptiles called pariesaurs which came from South African rock of much older age. Things only got worse from there.

In 1890 the naturalist Richard Lydekker realized that Owen had erred, and he instead attributed all the material to a pariesaur, but Lydekker was wrong, too. When the paleontologist Robert Broom looked at the same material in 1910, he saw that some parts definitely belonged to a dinosaur, which he thought was an ankylosaur. Franz Nopcsa disagreed, casting the fossils as belonging to a stegosaur in his own 1929 study, but it was not until 1981 that paleontologists P.M. Galton and W.P. Coombs straightened things out. The dinosaur was indeed a stegosaur, and is called Paranthodon africanus today.

Paranthodon was not the only cryptic stegosaur with a tortured history. As reviewed by Susannah Maidment in her new paper on the history of stegosaur discoveries, in 1874, just three years prior to the description of the famous Stegosaurus, the scrappy remains of another stegosaur were found in Bedfordshire, England. Described as a partial skull by H.G. Seeley—though actually part of a vertebra—Craterosaurus pottonensis was so incomplete that it was not recognized for what it was until the 1980s.

Another stegosaur, called Omosaurus armatus by Richard Owen (and known as Dacentrurus today), was found the same year in Swindon, England, though its discovery, too, was plagued by confusion over whether its armored plates belonged to the dinosaur or were the head plates of a giant fish. We can look back at them today as the first stegosaurs to be described, although the fossils that initially set the image of what this group was like were the specimens found by O.C. Marsh and E.D. Cope during the “Bone Wars” of the late 19th century.

We have come a long way since Craterosaurus, “Omosaurus,” and Stegosaurus were initially described. Since that time stegosaurs have been found in the Middle Jurassic to Early Cretaceous rock of North America, Europe, Africa and Asia, although the most familiar one is perhaps one of the strangest. Stegosaurus lacked the large shoulder spikes seen among other dinosaurs of its kind, and it had an alternating pattern of plates on its back rather than a combination of back spikes and plates arranged in straight double rows. Even compared to other groups of dinosaurs, though, the stegosaurs were among the most unusual groups of dinosaurs to have ever lived, and new discoveries—such as species with extra-long necks—continue to underscore how bizarre they were.

References:

Maidment, S. (2010). Stegosauria: a historical review of the body fossil record and phylogenetic relationships Swiss Journal of Geosciences DOI: 10.1007/s00015-010-0023-3

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Dinosaur Sighting: A High-Class Triceratops

A metallic Triceratops, photographed on the grounds of a Minneapolis mansion. Photo by Mark Ryan.

I never would have thought of Minnesota as a hot spot for dinosaurs, but reader Mark Ryan keeps sending in sightings from the Gopher State. His latest submission is of one of several metallic dinosaurs that once graced the lawn of a mansion in uptown Minneapolis. The question is, what dinosaur was it? It clearly had the elongated frill and brow horns of what has previously been called Torosaurus, but the solid frill is a dead giveaway for Triceratops. Given the new debate over whether “Torosaurus” is really just an adult Triceratops, perhaps this sculpture can be seen as a sort of transitional growth phase, though—since it was built many years ago and has recently disappeared from the lawn—I wouldn’t bet on it.

Have you stumbled across a dinosaur in an unexpected place? If you have, and have a photo of the encounter, send it to us via dinosaursightings@gmail.com!

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The Many Layers of Cretaceous China

In order to understand the ecology of any environment, past or present, you must be able to change the scale of your perspective. Large animals are readily apparent, but what about the interactions between the plants they eat, the insects on those plants, the pollen on those insects, the many microorganisms in the habitat and so on? It is practically impossible to keep all these parts of an ecosystem in mind at once, but if we alter the scale of our perspective, we can better appreciate a greater array of interactions that might otherwise go unnoticed.

Artist John Conway has just created a stunning example of the nested levels of interactions between organisms in a new video. The scene is of prehistoric China’s famous 133-million to 120-million-year-old Jehol biota. At first only the dinosaur Jinzhousaurus and a pair of the pterosaur Jeholopterus can be easily seen, but as the camera zooms in the wasp Tanychora beipioensis comes into view, and it is covered with the pollen grains Protoconiferous funarius. The painting is an amazing reminder that there was much more to prehistoric ecosystems than dinosaurs and the plants they ate, but how did Conway create it? In an interview with paleontologist David Hone on the Archosaur Musings blog, Conway briefly explained the method and motivation behind the piece:

It’s a series of paintings done in Photoshop at successively smaller scales, then stitched together and animated in After Effects.

I was looking for a way to get across the sheer breadth of scale in the fossil record, from dinosaurs to pollen in this case. I was also looking for a way to make picture of a biota without having to do a “menagerie” painting, which is otherwise a necessary evil if you want to get a lot of animals in the one scene.

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