A 3-dimensional CT reconstruction of Tyrannosaurus rex and Homo sapiens. The color schemes indicate multifactorial air-containing spaces within the very different skulls. The H. sapiens skull highlights the maxillary, frontal, ethmoid paranasal sinuses, and the endocranial cavity (light green, blue, fuchsia, and purple, respectively). The T. rex skull highlights the antorbital cavity (dark green) and the highly convoluted pneumatized areas around the nasal region (brown, gold, and dark purple). The illustrations exemplify the range of vertebrates investigated in this special issue which spans the geologic time scale from the Cretaceous (145–65 million years ago) to Quaternary (1.8 million years ago to present) periods. These images (provided by L Witmer and R Ridgely, Ohio University) illustrate the power of the sophisticated visualization techniques that allows the graphical inspection of the air sinuses.