Dinosaur senses primitive birds like "Archaeopteryx" and "Hesperornis". The optic nerve was large in "Carcharodontosaurus". Among dinosaurs, theropods had exceptionally large eyes. Deinonychosaurians, especially troodontids, had forward-facing eyes, suggesting stereoscopic vision and improved depth perception. Tyrannosauroid snouts allowed for a 55˚ binocular field of view, less than a modern human but more than their hadrosaurid prey. Dinosaur senses Dinosaur senses are difficult subjects of study for paleontologists since soft tissue anatomy rarely fossilizes. The three semicircular canals of the inner ear of "Allosaurus fragilis", when viewed from the side, had a subtriangular outline. This subtriangular inner ear configuration is present in "Carcharodontosaurus",
Specimens of Archaeopteryx that "Archaeopteryx" could have raised its short second toe in a similar manner to its dromaeosaur cousin "Deinonychus", whose second toe bore an enlarged "sickle claw" for probable use in predation. It remains unclear whether "Archaeopteryx" also used its hyperextended toe-claw in a similar fashion or for some other purpose. Taken together, many of the unique features of the skull, feet and coracoid strengthen a close relationship of archaeopterygids to deinonychosaurian theropods. Well-preserved imprints of wing and tail plumage show details of the barbs, but not barbules, and the shafts of 11 primaries can be counted on the right wing.