Sonorasaurus, meaning “Sonora lizard,” is a genus of brachiosaurid dinosaur from the Albian to Cenomanian stages of the Mid Cretaceous Period (112 to 93 million years ago). Its name was derived from the Sonoran Desert in Arizona where its fossils were first found. The remains were discovered by geology student Richard Thompson, in 1995.
Dating of the discovery makes Sonorasaurus the first known brachiosaur to have lived in the Mid Cretaceous Period of North America. The type species, S. thompsoni, named for its discoverer, was described by Ratkevich in 1998.
Sonorasaurus was a herbivorous sauropod estimated to have been about 50 feet long and 27 feet tall. It was about one-third the size of Brachiosaurus.