page_title: Alamosaurus
section_title: Habitat and geographic origin
hierarchical_section_title: Alamosaurus / Habitat and geographic origin
caption_attribution_description: Alamosaurus, autor - Bogdanov,2006
context_page_description: Alamosaurus is a genus of potentially opisthocoelicaudiine titanosaurian sauropod dinosaurs, containing a single ±known species, Alamosaurus sanjuanensis, from the late Cretaceous Period of what is now southern North America. Isolated vertebrae and limb bones indicate that it reached sizes comparable to Argentinosaurus and Puertasaurus, which would make it the largest dinosaur known from North America. Its fossils have been recovered from a variety of rock formations spanning the Maastrichtian age of the late Cretaceous period. Specimens of a juvenile Alamosaurus sanjuanensis have been recovered from only a few meters below the Cretaceous-Paleogene boundary in Texas, making it among the last surviving non-avian dinosaur species.
context_section_description: Skeletal elements of Alamosaurus are among the most common Late Cretaceous dinosaur fossils found in the United States Southwest and are now used to define the fauna of that time and place, known as the "Alamosaurus fauna". In the south of Late Cretaceous North America, the transition from the Edmontonian to the Lancian faunal stages is even more dramatic than it was in the north. 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.
  The appearance of Alamosaurus may have represented an immigration event from South America. Alamosaurus appears and achieves dominance in its environment very abruptly, which might support the idea that it originated following an immigration event. Other scientists speculated that Alamosaurus was an immigrant from Asia. However, critics of the immigration hypothesis note that inhabitants of an upland environment like Alamosaurus are more likely to be endemic than coastal species, and tend to have less of an ability to cross bodies of water. Further, Early Cretaceous titanosaurs are already known, so North American potential ancestors for Alamosaurus already existed.
  Contemporaries of Alamosaurus in the American southwest include the tyrannosaurid Tyrannosaurus, the oviraptorid Ojoraptorsaurus, the hadrosaurids Gryposaurus alsatei and cf. Kritosaurus, the armored nodosaur Glyptodontopelta  and the chasmosaurinae ceratopsids cf. Torosaurus utahensis, Bravoceratops, and Ojoceratops. Non-dinosaur species that had shared the same environment with Alamosaurus included the giant pterosaur Quetzalcoatlus, various species of fishes and rays, amphibians, lizards, turtles like Adocus, and multiple species of multituberculates like Cimexomys and Mesodma.
caption: Restoration
exif: {"Image Tag 0x000B": "ACD Systems Digital Imaging"}