Skeletal elements of "Alamosaurus" are among the most common Late Cretaceous dinosaur fossils found in the American Southwest and are now used to define the fauna of that time and place. There was a climate change in this area, it became drier, and this caused changes in the fauna. Thomas M. Lehman describes it as "the abrupt reemergence of a fauna with a superficially 'Jurassic' aspect". These faunas are dominated by "Alamosaurus" and feature abundant "Quetzalcoatlus" in Texas. The "Alamosaurus" "Quetzalcoatlus" association probably represent semi-arid inland plains.