Wishbone

What we call the wishbone, technically called the furcula, is really the fused collarbones. The wishbone is found between the two shoulder bones and the breastbone. Generally theropods have these fused collarbones and you can see the furcula or wishbone present in both Deinonychus and Gallus. It has even been documented in more primitive non-avian theropods like Allosaurus.

Originally the wishbone was thought to have evolved as an adaptation for flight. New evidence challenges this notion. To find the separate collarbones you must look to some ornithischian dinosaurs (e.g. Protoceratops) and the very primitive theropods (e.g. Coelophysis).

Wishbones from non-avian theropods are very rare fossils, and when found they are rarely attached to the rest of the skeleton. The specimen in the non-avian theropod photograph is actually from a tyrannosaur because so far there are no known Deinonychus wishbones. Because many scientists only recognized the wishbone as being a feature in modern birds, the wishbones that were found in non-avian theropods originally were not recognized as such and instead were sometimes mistaken for part of the series of belly ribs known as gastralia. So now collections need to be re-examined for the possibility of existing furcula labeled as the wrong part.