Name means: Reptile from the Ojo Alamo Formation


Species: sanjuanensis

Range: Late Cretaceous (Maastrichtian, 70-65 MYA) of New Mexico, Texas, and Utah

Size estimate: possibly 100 ft length, about 75 tons

Discovery: Charles W. Gilmore, 1922

Classification: dinosauria, saurischia, sauropoda, titanosauria, saltasauridae


Our image of Alamosaurus has transformed over the years. Charles Gilmore based this name on just a shoulder blade and a hip bone. Without much to go on, scientists and artists guessed the animal looked like Diplodocus. Since then we have found many more fossils from Alamosaurus and its relatives. They show that it more closely resembled Brachiosaurus, and may have grown even bigger. The sculpture you see here represents the older image of Alamosaurus, based on fossils from young individuals.


Alamosaurus roamed the southern end of an ancient landmass called Laramidia.  It shared its environment with the duck-billed dinosaur Gryposaurus, the horned dinosaurs Torosaurus, Ojoceratops, and Bravoceratops, and the giant pterosaur Quetzalcoatlus. In Utah it may have faced off against Tyrannosaurus rex. Though size probably protected most adults from attack, recent discoveries show that it grew bony armor plates on its rough hide.