Dinosaurs ruled Earth for 160 million years, but they didn't get that way by running everywhere. What little we can tell about dinosaur anatomy suggests they could barely run at all. But they could power walk...thanks to their muscular rumps.
Modern mammals and flightless birds share some common anatomical features in how they run. Specifically, we can tell with a fair amount of certainty how fast an animal can run based on the length of its strides. Paleontologists have been using that basic rule of thumb for decades to analyze fossilized dinosaur footprints, and all evidence suggests dinosaurs were slowpokes. What's more, fossil analysis has suggested that dinosaurs like T. rex lacked the proper build to run anywhere, in their case due to some rather weak knees.
But Heinrich Mallison of Berlin's Museum of Natural History is challenging that view. He argues that the structure of dinosaur hind limbs is markedly different from that of modern mammals and birds, meaning the stride formula isn't a good indicator of what dinosaurs can really do.
Instead, Mallison suggests we should look at the dinosaurs' buttocks - and no, there isn't a non-immature way to phrase htat - which had far more powerful muscles than their mammalian counterparts. While the dinosaurs probably couldn't run much, their butt muscles allowed them to take a ton of short, rapid strides, just like a power walker. If that's the case, T. rex could have moved quickly just fine even with weak ankles.
It's a fascinating idea, though unfortunately it does mean that we now have no way of knowing for sure how quickly dinosaurs ran. All I know is, I'm looking forward to a bunch of power walking tyrannosaurs showing up in Jurassic Park IV, preferably while chasing an also power walking, angry one-liner spouting Jeff Goldblum. That would be pretty much the peak of cinema history, as far as I'm concerned.