T. REX GOES TO HOSPITAL

New data reveals the tough lives of dinosaurs:

Dinosaur fossils often have bone fractures or evidence of infection and cancer. Palaeontologists are now using medical CT scans to discover more about dinosaur diseases.

Dinosaur fossils often have bone fractures, bite marks, or evidence of infection and cancer. Palaeontologists are using medical tools to make accurate diagnoses that reveal the animals’ illnesses and causes of death.

Sue needs water. Something in her mouth and throat is bothering the huge T. rex, as she limps towards a dry river bed – it feels like a chunk of meat that is too big to be swallowed. In her youth, Sue didn’t have these kinds of problems. Back then the dinosaur was a magnificent and ferocious predator boasting 13 metres of muscles from head to toe. Now she is about 30 years old and rheumatic. Hunger is gradually wearing down her body. Her bones are clearly visible under her skin, and pain darts through her legs and back with every step she takes. And now the throat problem is driving the animal crazy.

We know from analyses of her bones and teeth that this is how the final hours of Sue’s life must have been like when the dinosaur died some 65 million years ago, somewhere in South Dakota, USA.

Sue is one of the most complete, oldest, and biggest examples of the T. rex ever found. Her bones have been examined and described several times before, but now scientists are making brand new discoveries using advanced tools from the medical world, not only with Sue, but with other dinosaurs around the world.

Detailed CT scans of Sue demonstrate that in the final years of her life, this dinosaur was as battered as an old boxer who struggles with a long series of injuries. The most recent results have even prompted a probably theory for how Sue died. If correct, the creature’s killer was just as small as the T. rex was big.

Parasite blocked the throat

One of the scientists studying fossils using medical tools is Kirstin Brink, a palaeontologist and expert on bone and teeth development from the University of Manitoba, Canada. Brink has taken a close look at 3D images from CT scans of Sue’s teeth, and she believes that the cause of death is to be found in the giant mouth. She has not yet published her theory in a scientific journal, but as she explains to Science Illustrated, Sue has an almost complete set of teeth, of which 58 of 60 have been preserved. The longest one measures 30.5cm. Brink is especially interested in three small teeth located in the upper part of the mouth that were growing out when Sue died. That is quite normal, as Tyrannosauruses grow new teeth throughout life. But these three are mis-shapen, one of them highly bent and curved, as if subjected to pressure. The other two are growing into each other.

Sue’s disease exists in birds

Brink ruled out a genetic defect, as that would have affected more teeth. But it could have been the parasite Trichomonas. This is most famous for causing veneral disease in humans, but the parasite also exists in the beaks and throats of birds, and Brink knew that a team of American scientists had previously diagnosed Sue with Trichomonas.

But how did the parasite interrupt the growth of the three teeth? Brink analysed images of modern birds with Trichomonas and found an

explanation. Apart

from causing infection which breaks down the bone of the jaw, the parasite causes deposits in the throat, and rounded yellow wax-like projections. The disease is known as trichomonosis.

“In living birds we observe these yellow projections grow so big that they block the throat, so the bird is no longer able to swallow food, even drink, and then it dies of starvation and thirst. It is possible that the same thing happened to Sue,” Brink explains.

She now aims to test her idea by collecting CT scans of living animals with Trichomonas infection in the mouth.

“If we can find evidence of mis-shapen teeth due to infection in living animals, it would support my hypothesis about parasites killing Sue,” she explains.

One potential weakness about the theory is that we do not know for sure whether the parasite existed back in the era of dinosaurs. But recently, Brazilian scientists found fossil parasites in a dinosaur bone for the first time. Seventy microfossils were observed in a Titanosaurus bone. Although these belong to a species other than Trichomonas, the discovery demonstrates that dinosaurs did indeed have parasites.

Scientists peer into bones

Previously, researchers were able to describe only what they could see with the naked eye, or under a microscope on the rare occasions when they were allowed to saw off a fraction of bone. But in recent years, new technology has allowed them to study the fossils more deeply by means of CT (computerised tomography) scanners, which they often access in hospitals. Another option is micro-CT, which is the same technology but with a much higher resolution.

With these it is possible to peer into the bones, studying the structure and make-up of teeth and bones without destroying the fossils. The scientists can then look for the difference signatures of cancer, infection and fractured bones.

Some of the most recent examinations of Sue’s bones took place using a CT scanner in a hospital. Scientists from Berlin’s natural history museum cooperated with experts from the German capital’s Charité university hospital to make the scans possible.

The aim was to determine whether cancer or infection had caused two intergrown vertebrae and a thickened calf bone. Other possibilities had been ruled out by previous examinations.The CT scan revealed uneven extra bone tissue on the surface, characteristic of changes that follow infection. The bone was not mis-shapen in the way that happens following bone cancer.

But before confirming the diagnosis, the scientists embarked on a calculation of probability, using a family tree for dinosaurs’ closest modern relatives – reptiles and birds. Based on scientific literature they plotted data regarding infection and cancer cases onto the tree of both animal groups.

The analysis showed that 3.1% of the birds and 1.8% of the reptiles had cancer. But 32% of the birds and 53.9% of the reptiles had bone infection. Together with the fact that no evidence of cancer has ever been found in Tyrannosaurus bones, it is likely that Sue was suffering from infection.

Dinosaurs were bacteria bombs

Poor old Sue was troubled by bone infection, arthritis in her tail, and infection in her leg. It’s possible the leg infection was caused by the microbes in her mouth, as chronic bone infection can be due to infection somewhere else in the body spreading via the blood.

The lifestyle and behaviour of predatory dinosaurs may have provided optimum conditions for bacteria to spread. Numerous teeth marks on facial bones of Tyrannosauruses indicate that they fought with each other, over prey, territories, or partners.

This ‘superspreader’ behaviour was intensified by the fact that they were walking bacteria bombs. While predatory dinosaurs ate fresh meat – and even practiced cannibalism – they also ate dead animals.

Scientists from the US University of Tennessee have studied the remains of a ‘feast’ involving more than 2000 bones from herbivores and the Allosaurus, a predatory dinosaur from the Jurassic period. Some 28% of the bones include distinct bite, scratch,

and tear marks that could very well be due to attacks by other Allosauruses.

Under such circumstances, bacteria and other microbes could have spread from dead animals to living ones, and between the various participants of the feast. And bacteria could easily have found their way into their bodies via the mouth, and from cuts on their feet. Evidence of infection is often observed in the feet of predatory dinosaurs, used to tear up and hold onto the carcass they were consuming.

A young Allosaurus from Wyoming, USA, is an example of this. This dinosaur, known as ‘Big Al’, again had an array of injuries, but the worst was severe toe infection. And like Sue, Big Al would have had difficulties hunting due to the bone infection.

Yet both Sue and Big Al managed to survive for a long time despite of injuries.

The best explanation that palaeontologists offer for this is remarkable – that they were protected from starvation by living in a group. We do know that some herbivorous dinosaurs lived in groups, but it is still debated whether predatory dinosaurs lived together. Professor of Palaeobiology Philip Currie from the University of Alberta in Canada has a theory in which at least some Tyrannosauruses lived in groups. The theory is based on a discovery of 26 Albertosauruses – predatory dinosaurs that are related to the T. rex but were slightly smaller. The dead animals were of various ages, and they all died at the same time and place, perhaps in a fire or flood, indicating that they all lived together as a group. If Sue and Big Al also lived in a group or a family, they might have survived because the other group members allowed them to eat their scraps.

Hunting was unhealthy

Apart from the parasite and bone infection, Sue was troubled by a series of other defects, including shoulder-blade injuries, evidence of a detached arm muscle, and three broken ribs. According to scientists, all thee injuries might have been caused during a single event, in a fight with prey.

Predatory animals usually prefer to prey on young and weak animals, for obvious reasons that their success rate would be higher. But they sometimes attack prey that puts up a fight, such as horned dinosaurs weighing several tonnes. These had pointed horns, and were used to fighting each other.

According to another not-yet-published study made by geologist Andrew B. Heckert from the US Appalachian State University, Sue’s fighting injuries and other physical conditions may make her a typical example

of big predatory dinosaurs. Together with his students, Heckert is collecting data from scientific articles for a database covering dinosaur injuries and disease. He is already seeing patterns emerge. Predatory dinosaurs and horned dinosaurs such as Triceratops had the most injuries, presumably because they either hunted or were hunting, and possibly competing for food.

“Predatory dinosaur bones reflect a very active and aggressive lifestyle,” Heckert tells Science Illustrated. “Almost all the big predatory dinosaurs had several injuries. And considering how few fossils we find compared to all the dinosaurs that existed, and that the skeletons are not intact, we must assume that there were even more injuries than the ones that we see.”

The biggest herbivores – long-necked sauropods – are different. They were rarely troubled by injuries.

“That might indicate that their size protected them against predators,” says Heckert. “On the other hand, we see arthritis, which has to do with size and old age.”

Like other palaeontologists, Heckert is fascinated by the possibilities of gaining new knowledge about these animals’ lives from these ever-advancing medical techniques applied to the bones – both because the new knowledge of dinosaur diseases and injuries teaches us more about their biology, and because it can also reveal new details about their behaviour and way of life.

Age-related gout and arthritis

The examination of Sue’s bones tells the story of a hard life – and one which didn’t become any easier over time. As if parasites, infection and fractured bones were not enough, Sue developed further conditions as she grew older. Sue’s tail included signs of arthritis, while one of her arms reveals evidence of podagra, or gout, where uric acid crystals accumulate in the joints, causing pain. The condition affects both humans and animals that eat a lot of red meat and other proteins.

Nevertheless, this iconic T. rex had a successful life, living for 30 years in spite of all her diseases and defects. In the wild, few animals get to grow old .

Today, a younger version of Sue has gone on show in the Chicago Field Museum. Unveiled in 2020, a new and more accurate reconstruction of the T. rex shows the predatory dinosaur in her prime; the exhibition includes a full-scale version of Sue consuming a large animal (see right) back before Sue was troubled by the infection that prevented her from eating. It is, perhaps, how she would prefer to be remembered.