Stephan Lautenschlager is a biomechanicist (BI-oh-meh-KAN-ih-cizt). Such scientists study how living things move. At the University of Bristol in England, he’s been working out how widely some dinosaurs could stretch open their mouths to feed (or maybe yawn!). In his new study, he looked at theropods. Most theropod species were meat-eaters. Playing possum is known more scientifically as death-feigning or thanatosis. But it’s not acting. It’s not voluntary at all. It’s a built-in physiological defense system that is automatically triggered as a last-resort response to an otherwise inescapable death. The body’s nervous system sets off a cascade of neurochemicals and hormones that dramatically affect the function of the many parts of the brain, as well as organs throughout the body.

Ease of use: The easier a call is to get comfortable with, the sooner it can be put to good use. Mouth fatigue also plays a part in this—the less effort a call requires to blow, the more effective it will be.

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S. Perkins. Early tyrannosaurs would have feared this predator. Science News for Students. December 9, 2013.

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This is innovative research,” says Lawrence Witmer. He’s a paleontologist at Ohio University in Athens. Only within the past 5 years or so have paleontologists had the computer-modeling capability to do such analyses, he points out. The next step, he says, would be to include more realistically shaped muscles in those simulations. Studies of these relatives suggest that the muscles exert their greatest force when they are stretched about 30 percent longer than their resting length. In other words, if a relaxed muscle is 10 centimeters (4 inches) long, it pulls with maximum force when it is stretched to a length of 13 centimeters (5.1 inches). Also, a muscle typically can’t pull at all if it is stretched to 170 percent of its resting length, says Lautenschlager. Beyond that, a muscle can rip or be damaged in some other way. How big could they go? This image shows the biggest angles for the dinos’ maximum bite force (left) versus their maximum mouth opening. Lautenschlager et al./ Royal Society Open Science Versatility: A call that can make multiple sounds means you won’t need to switch to a different call as often, making for less movement and noise that will give you away. Holzman, Roi; Day, Steven W.; Mehta, Rita S.; Wainwright, Peter C. (10 June 2008). "Jaw protrusion enhances forces exerted on prey by suction feeding fishes". Journal of the Royal Society Interface. 5 (29): 1445–1457. doi: 10.1098/rsif.2008.0159. PMC 2607355. PMID 18544504.