Smithsonian.com

A restoration of a Tyrannosaurus called 'Peck's Rex' showing lesions in the jaw and mouth. From the PLoS One paper.

By now it should not surprise anyone that birds and theropod dinosaurs were closely related. Numerous discoveries have revealed that many “bird” characteristics, like feathers, first evolved in dinosaurs and were passed on to the avian descendants of one group of theropods called coelurosaurs. Tyrannosaurus was a coelurosaur, and while the question of whether it had feathers during any time of its life is still open for debate, a new study published in PLoS One shows that the “tyrant king” suffered from a disease that still plagues modern birds.

Conducted by paleontologists Ewan Wolff, Steven Salisbury, Jack Horner and  David Varricchio, the study took a closer look at a series of holes commonly seen in Tyrannosaurus lower jaws. These holes have previously been thought to be bite marks from another Tyrannosaurus or the result of some sort of bacterial infection in the bone. To test these hypotheses, the team looked at 61 tyrannosaurid skulls, approximately 15 percent of which displayed this jaw pathology.

The holes were inconsistent with damage that a bite from another predatory dinosaur would have inflicted. Bones are not static but living, and when they are damaged by physical trauma (like a bite) they react. If all these tyrannosaurids were bitten, it would be expected that the bones would show some inflamation, signs of bacterial infection and indications of healing after the event. Instead, the holes are smooth-edged and show no signs that they were made by the teeth of another dinosaur.

With dinosaur-on-dinosaur combat ruled out, the researchers looked at diseases that had been proposed to account for the damage. None of those previously suggested fit, but the bone pathology was consistent with damage done by a microorganism called Trichomonas gallinae that infects some modern birds. While some forms are virtually harmless to their host, others cause severe ulcers in the mouth and upper digestive tract of pigeons and birds of prey. Some of the tyrannosaurids appear to have suffered from the same sort of microbial infestation.

While paleontologists cannot be sure that the damage done to Tyrannosaurus was caused by the same species of Trichomonas, at the very least the study suggests that they were susceptible to a close relative of the modern organism and that this “avian” disease was already present over 65 million years ago. If this hypothesis is true, it is yet another line of evidence that links coelurosaurs closely to birds, even if Tyrannosaurus was more evolutionarily distant from birds than some of its “raptor” relatives.

Yet the paleontologists took their studies a step further. How could this harmful microorganism have been transmitted from dinosaur to dinosaur? In living birds Trichomonas gallinae is often taken up in drinking water by birds like pigeons, which are then preyed upon by hawks and other birds of prey. That tyrannosaurids drank water containing this kind of microorganism cannot be demonstrated, but their role as large predators would be consistent with disease transmission.

Rather than drinking up infected water, tyrannosaurids would transmit the microorganism through fights with each other or even eating the carcasses of infected individuals. While the holes in the lower jaw were not caused by such events, there is evidence that tyrannosaurids sometimes bit each other on the face. This would have allowed the microorganisms from the mouth of one dinosaur to enter the wounds opened up on another. The microorganisms would then infest the mouth and throat of the dinosaur, opening lesions in the flesh and bone. The Tyrannosaurus known as “Sue” presents one of the most severe cases; there were so many lesions in her jaw that she may have had trouble eating. With the infestation at such an advanced stage, the researchers suggest, the largest Tyrannosaurus yet discovered may have starved to death.

For the past several years the Walking With Dinosaurs live show has been enthralling audiences around the world with its life-size dinosaur puppets, but next week will see the opening of another impressive dino-spectacle that will soon be touring the United States.

Called “Darwin the Dinosaur,” the show is more concerned with good storytelling than scientific accuracy. After a scientist creates a dinosaur named “Darwin,” he quickly learns that he needs to give his predatory creation a heart. Darwin then meets a variety of other creatures, including another dinosaur who is not so friendly to the scientist who made Darwin. (There is even, believe it or not, a dinosaur lightsaber battle.) And the best part? The entire play is done in the dark. All of the characters are puppets made out of glowing wires, an artistic feat that is more difficult than it might sound at first.

The play will open on October 3 in Kansas, eventually followed by a national tour. I can’t wait to see it.

Our latest Dinosaur Sighting (and a special Monday edition since Friday brought the exciting news of Anchiornis) comes from the Denver Botanical Gardens, where this year’s fall maze is a Tyrannosaurus carved out of a cornfield. This bit of artistic gardening coincides with the park’s current “Jurassic Garden” exhibit, which features living relatives of prehistoric plants right alongside dinosaur statues.

If you have any photos of Denver’s “Jurassic Garden”, or have spotted a dinosaur in another place that you did not expect, send those pictures to dinosaursightings@gmail.com. You might see them featured here!

A restoration of Anchiornis, from the Nature paper.

Ever since the first skeleton of Archaeopteryx was discovered in 1861, the feathered dinosaur has been considered the oldest bird. During the last several decades, however, scientists have found that many “bird” features, such as feathers, first appeared among theropod dinosaurs. What defines a bird rather than a non-avian feathered dinosaur has become a much more complex issue. There is no better example of this than the recently-described Anchiornis huxleyi.

Earlier this year an international team of scientists described Anchiornis in the journal Chinese Science Bulletin. While the incomplete skeleton of the animal shared many traits in common with dinosaurs, the scientists hypothesized that the 155-million-year-old Anchiornis was the closest fossil relative of early birds like Archaeopteryx. Since the time that paper went to press, however, an even better specimen of Anchiornis has been discovered, one that caused the scientists to revise what they had thought about the dinosaur.

In next week’s issue of Nature, paleontologists Hu Dongyu, Hou Lianhai, Zhang Lijun, and Xing Xu present a revised take on Anchiornis based upon the new material. The fossil used for the first study consisted of a somewhat jumbled skeleton, not unlike the first skeletal specimen of Archaeopteryx, but a new exceptional fossil preserves almost the entire animal. It even includes feather impressions. Yet when the paleontologists studied this new fossil they discovered that their original study had placed Anchiornis too close to birds. Instead they found that Anchiornis was a feathered troodontid dinosaur, still a relatively close relative of the ancestors of the first birds but now a few steps removed. Despite the headline of a New Scientist story about the new study, Anchiornis was not the “earliest bird” but a non-avian feathered dinosaur that possessed some bird characteristics. Ed. Note — New Scientist has since corrected their headline.

Interestingly, though, the new fossil showed that Anchiornis is the third non-avian dinosaur known to possess long feathers on its hindlimbs. This feature was either inherited from a feathered common ancestor of dinosaurs like Anchiornis and Microraptor or evolved independently more than once. Given that Anchiornis is also at least five million years older than Archaeopteryx, it is definitive evidence that long feathers and other avian characteristics evolved in dinosaurs before the first birds took to the air.

Anchiornis and other feathered dinosaurs have shown beyond dispute that birds evolved from small theropod dinosaurs, but the precise relationships between feathered dinosaurs and their avian relatives are still being worked out. There are so many fossils turning up at such a fast rate that the evolutionary tree of feathered dinosaurs is constantly undergoing a lot of changes. Given the strong resemblance of Anchiornis to Archaeopteryx, one may even wonder if the celebrated “first bird” might eventually be shuffled into a different position in the feathered dinosaur family tree. That will be a matter for future studies to work out, and our new view of Anchiornis suggests that there are many more fossils of feathered dinosaurs and early birds out there waiting to be discovered.

The Great Dinosaur Discoveries by Darren Naish

There is no shortage of dinosaur encyclopedias available today. Each is organized a little differently and is aimed at a different audience, but there is a lot of overlap among them. The Great Dinosaur Discoveries, written by paleontologist Darren Naish, is a wonderful exception to this trend.

Rather than focus on the dinosaurs alone, Naish uses the history of science as a foil to illustrate how what we know about dinosaurs has changed over the past 200 years. The dinosaurs were are familiar with today would no doubt shock the Victorian naturalists who initially described them as enormous versions of lizards and crocodiles. This change did not come about instantaneously, and Naish’s book shows how scientific hypotheses intermingled with new discoveries to  shape our present understanding of dinosaurs.

This approach has been taken before, as in Edwin Colbert’s Men and Dinosaurs, but Naish’s book is a unique contribution. Not only does it serve as a sorely-needed update to books about how dinosaur science has changed, but is is lavishly illustrated. It is a pleasure just to flip through the pages and look at the photographs and artistic restorations.

Yet The Great Dinosaur Discoveries is much more than a glossy coffee table book. It is packed with scientific and historical information that will no doubt please a wide variety of readers. I particularly enjoyed Naish’s strategy for mixing the dueling historical and scientific narratives. The great discoveries are organized in chronological order and include the details of the discovery along with what we know now. This allows Naish to contrast the image of the dinosaurs when they were first discovered to what we have learned since. The entry for Megalosaurus, for instance, shows an early 1854 restoration of the dinosaur as a kind of crocodile/dog hybrid with a bold modern restoration of the predatory dinosaur running after a hapless herbivore.

Naish gives the same attention to detail to new discoveries, as well. The final section of the book, which focuses on discoveries made in the last decade, is an excellent overview of what dinosaur science is like today. As some paleontologists have noted, we are presently in a “golden age” for dinosaur studies; our understanding of them and their evolution is growing at an astounding rate. Almost every month major new discoveries are heralded in academic journals and important new finds are coming out of the ground fast and furious. While Naish has done an superb job making his book as up-to-date as possible, I have little doubt that he could already start working on an addendum to include all the new finds that have been announced since his book went to press.

The Great Dinosaur Discoveries is an excellent book for dinosaur enthusiasts of any stripe. It is a beautifully-produced volume that is among the best summaries of dinosaur science presently available. It will no doubt be beloved by professional paleontologists and young dino-philes alike.