structure within its interlocking prezygapophysis of its vertebrae, which formed a semi-rigid lattice, apparently to stop the tail from moving up and down. Coelophysis had a long narrow head (approximately ), with large, forward-facing eyes that afforded it stereoscopic vision and as a result excellent depth perception. Rinehart et al. (2004) described the complete sclerotic ring found for a juvenile Coelophysis bauri (specimen NMMNH P-4200), and compared it to data on the sclerotic rings of reptiles and birds and concluded that Coelophysis was a diurnal, visually oriented predator. The study found that the vision of Coelophysis was superior to most lizards' vision, and ranked with that of modern birds of prey. The eyes of Coelophysis appear to be the closest to those of eagles and hawks, with a high power of accommodation. The data also suggested poor night vision, which would mean this dinosaur had a round rather than a split pupil. Coelophysis had an elongated snout with large fenestrae which helped to reduce skull weight, while narrow struts of bones preserved the structural integrity of the skull. The neck had a pronounced sigmoid curve. The braincase is known in Coelophysis bauri but little data could be derived because the skull was crushed. Unlike some other theropods, the cranial ornamentation of Coelophysis was not located at the top of its skull. Low, laterally raised bony ridges were present on the dorsolateral margin of the nasal and lacrimal bones in the skull, directly above the antorbital fenestra. Distinguishing anatomical features A diagnosis is a statement of the anatomical features of an organism (or group) that collectively distinguish it from all other organisms. Some, but not all, of the features in a diagnosis are also autapomorphies. An autapomorphy is a distinctive anatomical feature that is unique to a given organism or group. According to Ezcurra (2007), and Bristowe and Raath (2004) Coelophysis can be distinguished based on the following features: the absence of an offset rostral process of the maxilla; the quadrate is strongly caudally; a small external mandibular fenestra, which is 9–10% of the mandibular length; and the anteroposterior length of the ventral lacrimal process is greater than 30% of its height. Several paleontologists consider Coelophysis bauri to be the same dinosaur as Megapnosaurus rhodesiensis (formerly Syntarsus), however this has been refuted by the following: Downs (2000) concluded that C. bauri differs from C. rhodesiensis in cervical length, proximal and distal