 Therefore, embryologists have identified the primary axis in birds as digit IV, and the surviving digits as II-III-IV.The fossils of advanced theropod (Tetanurae) hands appear to have the digits I-II-III (some genera within Avetheropoda also have a reduced digit IV).If this is true, then the II-III-IV development of digits in birds is an indication against theropod (dinosaur) ancestry.