I don’t know about you, but I haven’t seen any dinosaurs lately. I mean, I’ve seen lots of birds, some lizards, and the occasional crocodile, but none of those massive Jurassic Park-style dinos. For paleontologists who want to know how a 60- to 70-ton dinosaur got around, this lack of subjects to study is a bit of an obstacle. At Drexel University, researchers are 3D printing small scale robotic models of the legs of one of the largest dinosaurs ever found to figure out how it was able to keep itself moving.
Rendering of the massive Dreadnoughtus schrani, which weighed an estimated 65 tons (60,000 kg), making it the most massive land animal whose size can be confidently calculated, according to Drexel University scientists. In life, Dreadnoughtus was an herbivore that likely spent much of its life eating massive quantities of plants to maintain its enormous body size.Image: Illustration: Jennifer Hall/Drexel University
Fossils of Dreadnoughtus schrani were discovered in Argentina in 2005. This dinosaur, a species of titanosaur, is estimated to have been the same approximate size and weight of a Boeing 737, although the example that was found was only a juvenile and not yet done growing. As is, the femur that they dug up is a massive 1.8 meters in length, meaning that the dino stood about two stories tall at the shoulder and was probably something like 26 meters long.
Drexel University scientists say Dreadnoughtus schrani was substantially more massive than any other large dinosaur for which mass can be accurately calculated.Illustration: Lacovara Lab/Drexel University
The closest animal equivalent we have right now to a dinosaur like this is an elephant, and an elephant isn’t a very close equivalent at all [see comparison, right]. Dreadnoughtus was quite possibly the largest land animal that ever lived, and it’s a case study (albeit an extinct one) in what happens when a biological system reaches the top end of what’s possible with mass supported on legs. To figure out how Dreadnoughtus managed to walk, Drexel researchers have 3D scanned Dreadnoughtus leg bones, fixed the damage caused by 77 million years (give or take) of being part of a rock, reduced it to a manageable size, and 3D printed the result.
There are some features on the fossils themselves that show where tendons and muscles might have been attached, and modern dinosaurs like chickens (seriously) provide additional physiological suggestions. However, cartilage is trickier, and this is where the robot limb can help. By 3D printing cartilage and then attaching everything together with some motors, the physical model can be actuated and then analyzed with more accuracy than would be possible using a computer simulation.
Using a physical model like this enables you to iterate quickly. You can try different configurations, and if they don’t work, you rebuild the robot and tweak some things (like ligament attachment points) and maybe next time, it works better. After enough steps, you might end up with a robotic dinosaur leg that matches the features of your fossil, while also adding the ligaments, muscles, and tendons in an arrangement that results in a realistic walking gait, which is therefore a likely model of what the real dinosaur leg actually looked like.
There’s no real way to prove the accuracy of a robotic dino leg like this, but biological systems tend to converge on optimal solutions for things like structural support and mobility. If your robotic leg converges on the same things, odds are there’s going to be some significant similarities between the two, at least to the extent that you’ll be able to learn something useful.
[ Drexel ]
Evan Ackerman is a senior editor at IEEE Spectrum. Since 2007, he has written over 6,000 articles on robotics and technology. He has a degree in Martian geology and is excellent at playing bagpipes.