Box #22 in our count down is Kentrosaurus…
Kentrosaurus: the “Prickle Lizard”
Kentrosaurus was a rather small relative of Stegosaurus that lived in Late Jurassic Tanzania, Africa. It lived alongside the giant, long-necked Giraffatitan and small Dysalotosaurus. Its prickly spines and flexible tail helped it defend itself from predators like Allosaurus and Ceratosaurus, and perhaps even a creature that could be one of Spinosaurus’ earliest relatives, Ostafrikasaurus.
Kentrosaurus may be shorter than a human is tall, but any predator would think twice about tackling a creature like this one. Like the horns of modern animals, each spike had a bony core and was covered in a sheathe of horn, which would have grown a little more each year throughout the animal’s life. The fossil cores of these spikes can be over 2 feet long. Dinosaur fossils with preserved soft tissue show that the outer sheathe on claws and spikes can add at least 20% to the size of the core. The average human is just under 6ft tall, about 1.8m. That same average human can comfortably set a hand on Kentrosaurus’ back, which is somewhere between 4-5ft (1.4m). That makes each spike nearly as long as that average person’s arm, and there are 14 spikes on the tail and hips before they transition into plates in the front half of the body.
Just in case the prickly appearance alone isn’t enough, Kentrosaurus had a very long, flexible, muscular tail, and a relatively long neck. This means that it could easily turn its head to look directly at any predator trying to sneak up from behind, and it had a powerful swing that could reach any creature that tried to jump on it. Strong enough to break bones as surely as a club, just in case those spikes didn’t manage to poke anything vital.
The would be predator wants to stay away from the swinging tail and go straight for the head? No luck there either. Kentrosaurus could easily rock back on its hind legs and swing its head away at a moment’s notice. The only thing a hungry predator would get was a mouthful of lethal spikes.
Being able to raise up on its hind legs was also useful for more peaceful reasons, such as standing to reach higher branches. Even though it couldn’t really chew in the same way a sheep can, one study seems to show that Stegosaurus had the bite strength of a sheep, so it’s possible that Kentrosaurus had a sturdy set of chompers as well.
How do paleontologists determine the bite strength of Stegosaurus, or figure out that Kentrosaurus could swing its tail 180 degrees with greater force and speed than the best human baseball player swings a bat?
Bones have all sorts of nubs, ridges, and cavities that show where muscles, tendons, and other soft tissues attach as well as muscle size. We can look at living birds and reptiles to see how dinosaur muscles could be different from mammals, and get a good idea for proportional strength and endurance. Then, after putting all this information into a computer, the computer can simulate the motion and give us a good picture of what the animal could do. It’s not perfect, since the accuracy of the simulation depends on the data given to the computer, but it’s a good way to ask questions and inspire more questions. Then other paleontologists can try and repeat the tests and see if they come up with the same results in their simulations, or figure out a way to test the same movement with physical models.
Some questions can even offer an excuse to play with dinosaur toys. Or make a tiny sculpture out of polymer clay…