Herrerasaurus ischigualatensis (3D recon)

Herrerasaurus ischigualastensis is both the oldest-known and one of the most primitive of all known dinosaurs. While Herrerasaurus is probably not the actual ancestral dinosaurian species, it is the closest species yet discovered and so it gives our closest glimpse of what the ancestral dinosaur looked like. Accordingly, there is a great deal of interest in Herrerasaurus by researchers around the world who study the evolution of dinosaurs and other reptiles. As seen in this image, the small endocranial cavity indicates that Herrerasaurus had a simple tubular brain. From a simple structure such as this, the enlarged, complex brain of modern birds evolved. Pseudocolored 3D reconstruction of 635 0.5 mm CT slices, side view. Specimen is 32 cm long. (Sample courtesy of Universidad Nacional de San Juan, Argentina and Dr. Oscar Alcober, University of Texas at Austin)

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