Today's students were born well after the dramatic scientific reinterpretations of theropod dinosaur stance and metabolism of the late 1960s and early 1970s. Yet, if asked to draw a picture of "Tyrannosaurus rex," most of these students will likely draw an animal with an upright, tail-dragging posture, remarkably like the original 1905 description of this famous dinosaur. We documented this phenomenon by asking college (n = 111) and elementary to middle school students (n = 143) to draw pictures of "T. rex." On each drawing, we measured the angle of the spine from a horizontal surface. An average angle of 50-608 was found in drawings from all ages, which is within about 58 of the 1905 posture at 578. This is in striking contrast to images created by modern dinosaur scientists, which average between 0 and 108. In an effort to explain this pattern, we measured "T. rex" images in a wide variety of popular books, most of them for children, published from the 1940s to today. Since 1970, a gradually increasing proportion has represented "T. rex" with a more horizontal back (lower tail angle). Thus, popular books, while slow to change, cannot entirely account for this pattern. The erect "T. rex" stance continues, however, to dominate other areas of popular experience, such as toys and cartoons, which most American children encounter early in life. We hypothesize that older-style images long embedded in pop culture could lead to cultural inertia, in which outdated scientific ideas are maintained in the public consciousness long after scientists have abandoned them.