Bone Bites Tell Tales
Everyone knows that the way paleontologists find out about dinosaurs and other prehistoric creatures is by studying fossils. Mostly, these fossils are bones but sometimes they are footprints, plants, and even poop. Paleontologist Ron Stebler has a very unique collection of fossils that tell scientists a great deal about what life was like for dinosaurs in the Mesozoic. Ron likes to collect fossil bones that have what are called pathologies. This means that something happened to the animal during its life, or after it died, that left a mark on its bones.
Why are these pathologies important? Because they give us a picture of a dinosaurs life that a plain, unmarked bone cannot. For example, Stan the T. rex, one of the most famous T. rex fossils ever found, has a small hole in a bone at the top of his skull. This hole matches perfectly with a tooth from a T. rex. This evidence provides paleontologists with a couple of facts about the life of T. rex. First, that these huge predators fought among themselves and second, since Stan’s bite occurred years before he died, that these fights were not always fatal.
One of the most interesting types of bone pathologies for Ron are bones that were injured and then healed. These fall into two categories: 1) injuries from natural causes and 2) injuries from fighting. Natural causes range from abscessed teeth, just like people get, to broken bones from tripping and falling, to diseases like arthritis.
It is amazing how many dinosaur bones show injuries from combat that the animal survived. Sometimes these bones show only a little healing, which can mean that the animal died from the injury a short time after the attack, maybe a week or two. Or it can mean that the animal was weakened enough from the first attack that it became too slow to escape another attack a few days later.
Bone pathologies can also show scientists how powerful some animals were. For example, one of the bones Ron has in his collection is a leg bone of a hadrosaur that was bitten in two by a single bite from a large predator. Since the only large predators at that time and place were T. rex, this had to have been a T. rex attack. Using this information, scientists can figure out the amount of force needed to cause this kind of damage and calculate how much power was in the bite of T. rex.
If you want to know how rough life for a dinosaur could have been, here is a partial list of the healed injuries on one dinosaur, a large Allosaurus known as Big Al:
• Two infected and fractured fingers on right hand
• Fractured finger on the left hand
• Infected right shoulder
• Fracture to the left hip bone
• Fractured left leg bone
• Infected right foot bone
• Fractured tail vertebrae
• Fractured stomach ribs
Many of the pathologies seen on fossils are tooth and claw marks that were made either at the time the animal was killed or while it was being eaten. One famous bone is nicknamed “T. rex biscuit.” It is the large upper leg bone of a Triceratops that shows many bite marks and claw marks. If studied carefully, this bone tells an interesting story. First, there is a big hole right through the bone. A large T. rex tooth fits perfectly into this hole. It would have taken a really viscous bite to make this hole, so scientists conclude that this bite was made during the fight that killed the Triceratops. Once its prey was dead, the T. rex didn’t have to use such force, so the other marks left by large teeth are not as deep. The other marks on the bone are from the teeth and claws of much smaller dinosaurs. This can be evidence of two things; it can mean that T. rex took the bone back to its nest where hungry babies put their sharp little claws and teeth into the bone while tearing meat from it, or it can mean that after the big T. rex ate its fill, much smaller carnivores finished off the carcass.
Recently, we asked Ron’s opinion about the argument that T. rex was not a hunter, that it may have been a scavenger that only ate animals that were already dead. Ron laughed at the suggestion and showed us one of his larger fossil bone pathologies. It is the entire hip section of a duck-billed dinosaur that would have been about 15 feet (5 m) long. There is a large section of the bones on the top of this hip missing, and there is no healing, so this was definitely a fatal injury. Ron then took a full size model of the jaws of a T. rex and they fit perfectly into the missing section of the hips. “This was a T. rex bite, there is no doubt,” Ron said. “No other predator was tall enough to have been able to bite from above like this, and the fit is perfect. This animal was probably trying to run away from a big rex and wasn’t quite fast enough. I doubt if it was sitting there, waiting to be chomped on .” This seems to be pretty strong evidence that T. rex was hunting by chasing down and killing a good sized dinosaur.
Ron has hundreds of bone pathologies in his collection, each one telling a different story about the life and death of prehistoric animals.
This photo shows the upper leg bone of a smaller duck-billed dinosaur. The tooth is from a T. rex and was placed there to show how paleontologists piece together the puzzles of fossil bones. The hole in the bone and the way it snapped show that a single tooth punctured the bone and snapped it in two. This bone shows how powerful the bite of T. rex would have been – if it wasn’t the fatal bite, it certainly stopped the poor duckbill from running away.
Another victim of T. rex, these are parts of the arm of a duckbill dinosaur. These are not killing bites, they are feeding bites, showing teeth that scraped the bone while tearing off the flesh.
This is part of a hip bone from a dinosaur that lived in Africa. There are a couple of interesting things about this bone. First, it is from a carnivore, which shows that it wasn’t only the plant eaters that were being eaten. Second, they are feeding marks, which means that it may have died naturally before being eaten. The bone is probably from a medium sized predator called Deltadromeus. The large carnivore at that time and place was Carcharodontosaurus, but the tooth marks are too small to come from that dinosaur. Ron suspects that these feeding marks were made by Afrovenator, another medium sized African predator.
The round holes in this duckbilled dinosaur rib section are called compression bite marks. The holes were made with a large, blunt-tipped tooth (the kind that a T. rex has!) The way the marks were made show that the attacker bit down and then took a second bite, moving its mouth a little to one side.
Sharks lived at the time of the dinosaurs, sharing the seas with large, vicious sea-dwelling reptiles. These reptiles would get much bigger than any of the sharks that lived during the Mesozoic, but when the reptiles were smaller, they might fall prey to the sharks. That seems to be the case with this fossil of the jaw of a sea-reptile called a mosasaur. It shows many bite marks made by shark teeth, one of which was stuck in the jaw. Sharks would lose many thousands of teeth during their lifetime.
This is the tail of a mosasaur, a sea-dwelling reptile. This fossil was discovered in Kansas, which was under a shallow sea during much of the Cretaceous Period. The tail shows bite marks that were probably made by a shark. These are small clues, but they are important in understanding prehistoric life.