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A pair of Mapusaurus threaten a young Argentinosaurus. By paleo-artist Luis Rey.

There is no question that Tyrannosaurus rex was a predatory dinosaur. It was a gargantuan animal with immense jaws lined with railroad spike-size teeth that could be slammed into a prey animal with enough force to puncture bone. At first glance it might seem that the answer to the question “What did Tyrannosaurus rex eat?” would be “Anything it wanted,” but in a new paper published this week in the journal Lethaia, paleontologists David Hone and Oliver Rauhut explain that the truth about the feeding habits of Tyrannosaurus and other large predatory dinosaurs is a lot more complicated.

For years it has been hypothesized that Tyrannosaurus and its close relatives (like Daspletosaurus and Albertosaurus) actively crushed and ingested bones as part of their regular diet. Compared to other large theropods, like Allosaurus and Giganotosaurus, the tyrannosaurids had very robust skulls and teeth that appeared to be adapted to crunching bones and not just shearing flesh. Strangely, though, traces of this kind of feeding behavior are rare. Throughout the dinosaur fossil record the few bones that have been found with theropod toothmarks on them contain scrapes and punctures that suggest that such contact with bone was accidental. Direct evidence of large predatory dinosaurs actively biting bone in order to consume it, like traces readily seen in the later mammal fossil record, is all but absent.

That large theropods ingested some bones is a certainty, though. Coprolites (or fossilized dino dung) from large theropods often contain scraps of bone, and these dinosaur probably ingested fragments of ribs, vertebrae, and other relatively small bones while feeding. This was not exploitation of bone as a food resource by itself, as seen among modern spotted hyenas, but a by-product of other feeding habits. This would make even more sense if, as Hone and Rauhut suggest, large theropods preferentially fed upon juvenile dinosaurs.

A documentary scene involving a pack of Allosaurus attacking an adult Diplodocus makes for a compelling restoration, but Hone and Rauhut argue such events were probably rare. It would be difficult, and very dangerous, for even large theropods to take down such a large animal. Instead large theropods probably fed upon sick, old, and young individuals, just like large carnivores today. If this is correct it could explain why juvenile dinosaurs are rare in the fossil record and why they are often found in groups.

There is no doubt that large theropods at least sometimes attacked adult prey animals, but juveniles would have probably made for much easier prey. Likewise, juvenile animals would be small enough that large theropods would not have been able to avoid ingesting at least a few bones while feeding on the smaller animals. Thus the presence of bone in coprolites and the lack of bones bearing evidence of theropod consumption is reconciled.

As Hone and Rauhut note, however, hypotheses about how theropods hunted and consumed prey will by tested by further evidence. It may be that fossils that might help us understand the habits of large theropods were not recorded or destroyed during excavations, and it would be helpful if paleontologists could keep these kinds of questions in mind while in the field or studying old specimens. At present it does not appear that large theropods regularly crushed large bones for consumption, but it would be fantastic if evidence that they did could be found!

For more on this research see Dave Hone’s Archosaur Musings blog.

The skeleton of Nothronychus. The recovered parts are in white. From the Proceedings of the Royal Society B paper.

Everybody knows that dinosaurs like Tyrannosaurus and Velociraptor were meat eaters, but what might come as a shock is that some of their close relatives often ate plants.

When I was a kid things were simple. Theropod dinosaurs were meat-eaters and all the rest were plant-eaters. Since the 1980s, though, numerous discoveries have shed light on a group of coelurosaurs (the group of theropods to which Tyrannosaurus and Velociraptor also belong) called therizinosaurs. These dinosaurs had beaks, small heads, long necks, barrel-shaped bodies, and long arms tipped with huge claws, yet some of them had feathers and they were close relatives of the dinosaurs that gave rise to the first birds. One such therizinosaur was Nothronychus, and a nearly complete skeleton of this dinosaur was just announced in the journal Proceedings of the Royal Society B.

The approximately 90-million-year-old Nothronychus was originally described from bones found in the American southwest in 2001. There was enough of it left to tell that it was a therizinosaur, but this new skeleton, found in southern Utah, is much more extensive. As such it provides for better evolutionary comparisons not only to other therizinosaurs, but to other coelurosaurs as well.

What the researchers found was that the therizinosaurs were rooted near the base of the maniraptoran family tree (the maniraptorans being that group of coelurosaurs that contains the ornithomimosaurs, dromaeosaurs, birds, and a few others). In other words, the earliest members of the therizinosaur lineage split off before the first members of other maniraptoran dinosaurs did. What makes this especially interesting is that this placement seems to reveal some important shifts in coelurosaur evolution.

It appears that the earliest coelurosaurs (including the ancestors of the tyrannosaurs) were hypercarnivorous, or that they only ate meat. Interestingly, though, several groups of dinosaurs near the base of the maniraptoran family tree show adaptations for plant eating; the dromaeosaurs (or “raptors”) are the only members of this larger group that appear to have exclusively eaten meat. Rather than being an abnormality, herbivory might have been rather common among the maniraptorans.

What this suggests is that the last common ancestor of the maniraptoran dinosaurs might have been herbivorous or omnivorous. This hypothesis will have to be tested and re-tested as more fossil evidence comes to light, but if the researchers are correct then sometime around 160 million years ago there lived an omnivorous or herbivorous dinosaur ancestral to all maniraptorans. Rather than being the rule, predators like Velociraptor might have been oddballs compared to the rest of their close kin.

The skeleton of Diplodocus on display in Berlin

In museums all over the world, skeletons of sauropod dinosaurs are reconstructed with their heads held high. It seems like the most natural position for these animals, but a short letter recently published in Science has questioned whether it is correct. According to biologist Roger Seymour, sauropods more likely kept their heads low to the ground, swinging them from side to side to vacuum up plant food.

The problem with sauropod posture is that their necks are ludicrously long. It would take a huge amount of blood pressure, generated by a massive heart, to keep blood pumping to the brain. This would be made all the more difficult if the animals held their heads high in the air, as the blood flow would have to work against gravity. For this reason Seymour favors the idea that sauropods kept their heads down and mostly moved them horizontally.

In a reply, paleontologists P. Martin Sander, Andreas Christian and Carole Gee agree that sauropods may have preferentially kept their heads at a relatively low level, but it was still possible that sauropods raised their heads high. That sauropods could do so is known from skeletal evidence, and it is possible that sauropods had physiological mechanisms to solve this problem that are not seen in living animals. It would take a lot of energy for a sauropod to raise its neck up high, but if the food it was reaching was high quality, or provided a large nutritional benefit, the reward might be worth the stress. The ability of sauropods to reach up high may have even benefited them during harsh conditions, when they could physically reach a wider array of resources than other dinosaurs.

Unfortunately, much of how sauropods used their necks, particularly in feeding, remains contentious. So much of the debate rests upon sauropod physiology that without a living animal to study the arguments will continue. That is what makes for compelling science, though, and who knows what new discoveries might shed light on this old problem.

Tyrannosaurus, from the paper by Sampson and Loewen. The grey areas represent the parts of the skeleton they recovered.

For years, one of the cardinal sins of paleontology illustration was showing a Tyrannosaurus attacking a sauropod dinosaur. Most of the long-necked earthshakers had disappeared from North America by the time the most famous of carnivorous dinosaurs came along, and so any scene depicting them together could immediately be ruled inaccurate. Truth certainly is stranger than fiction, however, as a paper published in 2005 brought Tyrannosaurus and one of the last North American sauropods together.

In 1922, the paleontologist Charles Whitney Gilmore described the titanosaur Alamosaurus, named for the Ojo Alamo Formation in which it was found. (The same formation is known as the Kirtland Shale today.) It was a late-surviving sauropod genus that lived in the Late Cretaceous, long after the heyday of more famous genera like Apatosaurus and Diplodocus, but did it have reason to fear Tyrannosaurus?

That Alamosaurus and Tyrannosaurus met was certainly a possibility, but until recently there was no direct evidence to confirm it. That changed when paleontologists Scott Sampson and Mark Loewen published a 2005 paper documenting a partial Tyrannosaurus skeleton from the North Horn Formation. The site had already yielded Alamosaurus bones and so it clinched the connection between predator and prey. Fossils of hadrosaurs and horned dinosaurs had also been found in the area, so it appears that Tyrannosaurus would have had the opportunity to dine on a diverse array of herbivores.

I would have thought that the presence of Tyrannosaurus and Alamosaurus in the same place would have immediately set paleo-artists to work imagining scenes of clashes between the two. To the best of my knowledge, however, no such illustrations exist. I would give it a try, but as has been extablished, my talents lie outside the realm of art.

Scutellosaurus and Other Small Dinosaurs by Dougal Dixon.

Kids really know their dinosaurs. If you don’t believe me, just try to tell a young dino-phile that the big, long-necked one is called “Brontosaurus” and you are sure to get an earful. Indeed, children can be extremely attentive in their study of the prehistoric world, and sometimes they catch mistakes even adults have missed.

A few weeks ago, first grade student Emilio Lemeni checked out a book called Scutellosaurus and Other Small Dinosaurs from the library of Rosa Parks Elementary School in Woodbridge, Virgina. It featured an array of dinosaurs and included a colored key explaining whether they were herbivores or carnivores. Among the dinosaurs featured in the book was the tiny predator Bambiraptor, but Emilio thought there was something not quite right about its description. According to the School Library Journal:

“An animal attacked by a pack of these dinosaurs [Bambiraptor] would have had little chance of surviving,” the book read. But when Lemeni glanced at the accompanying image at the top left corner of the page, he saw a green dinosaur, clearly an indication that it was a plant eater.

The illustration of Bambiraptor itself was fine but the key was the wrong color. Only herbivores had a green dinosaur key, and Bambiraptor certainly wasn’t a peaceful plant-easter eater (Ed. Thanks Claire!). Emilio told the school librarian about this and she, in turn, called the publishing company. They acknowledged they had made a mistake and sent a letter of appreciation to Emilio, followed by a collection of dinosaur books for him and his classmates.

The publisher has also promised a correction when the book is reprinted, and they have offered another solution for those who have already purchased the book:

SLJ contacted Capstone Publishers, parent company of Picture Window, regarding the error. “We’ve come up with a ‘green’ option that will allow us to use the remaining stock of the title and provide customers with a more immediate fix to the mistake: a sticker,” explains company spokeswoman Jennifer Gidden. “We will be correcting our mistake upon reprint of the title.”

Emilio saw something he thought was wrong, brought it up, was shown to be right, and he made his school proud. Given that Emilio has already had this practice with peer-review he could very well grow up to be a fine paleontologist if he wanted to.

Happy Thanksgiving, everyone! The Smithsonian staff will be taking the day off tomorrow to gather with family and eat our preferred turkey variant (turkey, tofurkey, turducken, etc.).

So, with food on everyone’s minds, now seemed as good a time as any to address the inevitable question: What did dinosaurs taste like?

And, yes, the inevitable answer: Chicken.

Well, possibly chicken. The best clue comes from two studies conducted in 2007-2008, by John Asara of Harvard Medical School and Mary Schweitzer of North Carolina State University (whose work on soft tissue in dinosaurs was described in Smithsonian magazine’s “Dinosaur Shocker.”) As the Washington Post reported:

“Protein retrieved from a 68 millon-year-old Tyrannosaurus rex bone closely resembles the main protein in chicken and ostrich bones and is only distantly related to lizards’, strengthening the popular idea that birds, and not reptiles, are the closest living relatives of dinosaurs.

In the new analysis, the team compared the order of 89 amino acids from the T. rex sample to the equivalent collagen sequence from a chicken, an ostrich, an alligator and a green anole lizard, a reptile commonly used in laboratory research.

The results indicate that T. rex, chickens and ostriches are evolutionary siblings, all descended from a single unidentified predecessor. Alligator collagen is more distantly related, and lizard collagen is more distantly related still.”

When the research team first released their findings in 2007, the New York Times wryly observed: “The scientists resisted being drawn into speculation on the likely taste of a T-rex drumstick.”

But, by 2008, Asara felt sure enough of his latest study to note, “Based on this data, you can be very confident that T. rex would taste more like chicken than it did last year.”

Our distant ancestors could have confirmed this theory—and, no, I’m not talking about cavemen like the fur bikini-clad Raquel Welch in One Million Years B.C. I’m referring to a shrew-like mammal named Repenomamus robustus, which lived 130 million years ago. In 2005, scientists at the American Museum of Natural History in New York announced they had found a fossilized specimen, with a baby dinosaur still in its gullet. “This is the first direct evidence that mammals fed on dinosaurs,” said Jin Meng, a paleontologist at the museum. “Now we can say that dinosaurs could be very tasty, which is good news.”

Well, good news if you’re not a dinosaur. In the meantime, the precise answer to the question of what dinosaurs tasted like will remain a mystery.

However, this much we know for certain: They weren’t kosher.

Duria Antiquior -- Early Dinosaur Drawing

At the beginning of the 19th century, paleontology was a new branch of science. People had been picking up fossils and trying to determine their significance for as long as anyone could recall, but the study of organic petrifactions was something new. Shells and teeth laid down in ancient marine environments were common, but so were strange spiral-shaped bodies. They were often referred to as “fossil fir cones,” as they looked like the cones that fell from pine trees, but geologist William Buckland came to a different conclusion. The fossil “cones” were really petrified dung, which he called “coprolites.”

Buckland was fascinated by the objects, as was one of his artistically-inclined colleagues, Henry de la Beche, who satirized Buckland in a drawing called “A Coprolitic Vision.” The viewer sees Buckland standing before the entrance of a cave, surrounded by prehistoric creatures simultaneously struck by diarrhea.

More famous was de la Beche’s vision of ancient Dorset, “Duria Antiquior.” (see above) Featuring ammonites, plesiosaurs, ichthyosaurs, and crocodiles, it was one of the first ecological reconstructions of ancient life (albeit one in which nearly every creature was attempting to consume another). As a finishing touch, de la Beche had many of the creatures leaving a trail of fecal deposits that would, in the course of geologic time, become coprolites. (If you look carefully at the image above, you can see some of the droppings under the animals. This was de la Beche’s work as originally intended.)

This is not the version of the painting that most people have seen, however. Perhaps the defecating creatures proved to be distasteful to other Victorian scientists, so de la Beche made another version without the trail of dung, and that illustration appeared in books. The drawing without the fecal matter was sold to help support of one of the greatest fossil hunters ever, Mary Anning. She came from a poor family, and most of her rather meager income came from selling fossils. Buckland was one of her patrons. Even though she was not always given due credit for her discoveries at the time, the geologists she knew organized to financially assist her, and the sale of de la Beche’s painting was one such effort. Desire to help a friend was more important than potty humor.

Image from The Life and Correspondence of William Buckland

When I was in elementary school, I was taught that one of the ways to tell a reptile from a mammal was by looking at their teeth. Reptiles, like lizards and crocodiles, had a mouth full of nearly identical teeth, while mammals had more diverse dental toolkits. This “rule” might work some of the time, but there are plenty of exceptions to it. Some mammals, like dolphins, have teeth that are the same throughout their jaws, while animals that would be expected to have a full set of identical teeth have specialized teeth.

One such animal that broke the rule was Heterodontosaurus, a small ornithischian dinosaur that had some cone-shaped teeth in addition to grinders for mashing up plants. For many years paleontologists have thought that the sharp teeth may have been used in competition for mates, and were secondary sexual characteristics that became developed as the animals matured. It may be strange to think of herbivores as being “saber-toothed,” but it is not as uncommon as you might think. Male musk deer and muntjacs (see my photo above), for instance, have large canine teeth that are likely a product of sexual selection. During the mating season, when competition for mates can be fierce, males often use these teeth to inflict deep wounds on their opponents.

A new juvenile Heterodontosaurus skull described in the Journal of Vertebrate Paleontology provided an important test of this hypothesis. If the fangs of this dinosaur were used in competition for mates, juvenile specimens would not be expected to have large, canine-like teeth. And the teeth would be expected to be more developed in the sex that was fighting for access to mates. (In most but not all modern animals, that’s the male.)

Contrary to these expectations, however, the juvenile Heterodontosaurus skull had large canine-like teeth. It is unlikely that they are the products of sexual selection. Why, then, did these dinosaurs have fangs?

The early appearance of the teeth, the authors of the paper suggest, is a crucial clue. If the sharp, conical teeth at the front of the dinosaur’s mouth appeared at such a young age, perhaps Heterodontosaurus was omnivorous. It’s also possible that the teeth could have served a role in defense, although it seems more likely that they were primarily adaptations to feeding.

Unfortunately, the authors went no further than stating that the sexual selection hypothesis is not supported and that the omnivory hypothesis merits further investigation. Although it has been widely reported that these dinosaurs may have eaten meat, there is not yet enough information to confirm or refute that idea. Simply because an animal has sharp teeth does not mean that it was a meat-eater. Lemurs, for instance, have long canines, but they use them to open the tough outer coverings fruits. Perhaps Heterodontosaurus did something similar, using its sharp teeth to break into the tough skins or shells of some plant foods.

Either way, the sharp teeth of Heterodontosaurus allowed for the authors of the paper to make another prediction. The two great branches of the dinosaur family tree, the Ornithischia (to which Heterodontosaurus belongs) and Saurischia (sauropods and theropods) once shared a common ancestor. As far as is currently known, that common ancestor was probably a small, bipedal, carnivorous dinosaur. Given that Heterodontosaurus has been placed close to the bottom of the Ornithischian family tree, it may represent a transitional stage between carnivory and herbivory. This does not mean that Heterodontosaurus was ancestral to all later herbivorous ornithischians, but that it might illustrate the shift to herbivory that occurred in this group of dinosaurs.