Do the hop

Natural History, Sept, 2005 by Sondra F. Messina

In "Bird's-eye View" [5/05] Matthew T. Carrano and Patrick M. O'Connor examined modern birds to gain a better understanding of the birds' dinosaur ancestors. But has anyone ever considered whether theropods might have "hopped" like birds, and if these hops could have been a preliminary aid to the motion of flying? A related question occurred to me from my reading Laurence A. Marschall's review of Birdsong: A Natural History [6/05]: did dinosaurs have a syrinx, which would have enabled them to make bird sounds?

Sondra F. Messina

Fresh Meadows, New York

MATTHEW T. CARRANO REPLIES: Some paleontologists have theorized that, based on the anatomy and orientation of theropod hip bones, the particularly birdlike theropods may have been hoppers. More recent work, however, suggests that those dinosaurs were still primarily walkers and runners. Some dinosaurs may have jumped or hopped occasionally, but the characteristic hopping of many small songbirds is probably a specialized feature of advanced birds, not something they inherited from their dinosaurian ancestors.

Similarly, dinosaurs almost certainly lacked a syrinx. The structure is highly specialized only in certain kinds of songbirds, and it was missing in the small theropod Scipionyx, the only dinosaur fossil for which traces of a trachea have been preserved. It was probably missing in the earliest birds as well.