Comparing the sinuses in some newly studied dinosaur bones from Argentina with bird anatomy, this learn node from the Public Library of Science lets students go online to peer over the shoulders of working scientists. The drawing is from Figure 1 in the article. In their recent work concerning the the anatomical relationships of dinosaurs and birds, the scientists here tell us:
In this paper, we describe a new large-bodied theropod from the Late Cretaceous of Argentina, Aerosteon riocoloradensis gen. et sp. nov., characterized by cranial and postcranial bones that are exceptionally pneumatic. Some of its postcranial bones show pneumatic hollowing that can be linked to intrathoracic air sacs that are directly involved in lung ventilation. As a result of an extraordinary level of pneumatization, as well as the excellent state of preservation of much of the axial column and girdles, Aerosteon helps to constrain hypotheses for the evolution of avian-style respiration.
For background on the general subject, the University of California Museum of Paleontology has an overview article: Are Birds Really Dinosaurs?