Earliest known - The earliest and most primitive known dinosaur is the Herrerasaurus discovered in 1989 at the foot of the Andes in Argentina by an expedition led by Paul Sereno of the University of Chicago, IL. Named after Victorino Herrera, a fossil hunter responsible for the discovery of fragments of bone many years earlier, this bipedal carnivore is believed to be nearly 230 million years old. The almost complete skeleton suggested that this predator stood 6 1/2-8 ft tall and weighed over 220 lb. Despite its otherwise primitive features, the Herrerasaurus had a dual-hinged jaw, which did not appear in other dinosaurs for another 50 million years, anticipating a turning point in the evolutionary process. (Artwork: Matthew Hillier for Guinness Publishing)
