page_title: Alamosaurus
section_title: History
hierarchical_section_title: Alamosaurus / History
caption_attribution_description: English: Alamosaurus mount in Perot museum עברית: אלמוזאורוס
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: Alamosaurus remains have been discovered throughout the southwestern United States. The holotype was discovered in June 1921 by Charles Whitney Gilmore, John Bernard Reeside and Charles Hazelius Sternberg at the Barrel Springs Arroyo in the Naashoibito Member of the Ojo Alamo Formation (or Kirtland Formation under a different definition) of New Mexico which was deposited during the Maastrichtian stage of the Late Cretaceous Period. Bones have also been recovered from other Maastrichtian formations, like the North Horn Formation of Utah and the Black Peaks, El Picacho and Javelina Formations of Texas. Undescribed titanosaur fossils closely associated with Alamosaurus have been found in the Evanston Formation in Wyoming. Three articulated caudal vertebrae were collected above Hams Fork, and are housed at the Museum of Paleontology, University of California, Berkeley. These specimens have not been described.
  Smithsonian paleontologist Gilmore originally described the holotype, USNM 10486, a left scapula (shoulder bone), and the paratype USNM 10487, a right ischium (pelvic bone) in 1922, naming the type species Alamosaurus sanjuanensis. Contrary to popular assertions, the dinosaur is not named after the Alamo in San Antonio, Texas, or the battle that was fought there. The holotype, the specimen the name was based on, was discovered in New Mexico and, at the time of its naming, Alamosaurus had not yet been found in Texas. Instead, the name Alamosaurus comes from Ojo Alamo, the geologic formation in which it was found and which was, in turn, named after the nearby Ojo Alamo trading post (since this time there has been some debate as to whether to reclassify the Alamosaurus-bearing rocks as belonging to the Kirtland Formation or whether they should remain in the Ojo Alamo Formation). The term alamo itself is a Spanish word meaning "poplar" and is used for the local subspecies of cottonwood tree. The term saurus is derived from saura (σαυρα), Greek for "lizard" and is the most common suffix used in dinosaur names. There is only one species in the genus, Alamosaurus sanjuanensis, which is named after San Juan County, New Mexico, where the first remains were found.
  In 1946, Gilmore posthumously described a more complete specimen, USNM 15660 found on June 15, 1937 on the North Horn Mountain of Utah by George B. Pearce. It consists of a complete tail, a right forelimb complete except for the fingers — which later research showed do not ossify with the Titanosauridae — and both ischia. Since then, hundreds of other bits and pieces from Texas, New Mexico, and Utah have been referred to Alamosaurus, often without much description. Despite being fragmentary, until the second half of the twentieth century they represented much of the globally known titanosaurid material. The most completely known specimen, TMM 43621-1, is a recently discovered juvenile skeleton from Texas, which allowed educated estimates of length and mass.
  Some blocks catalogued under the same accession number as the relatively complete and well-known Alamosaurus specimen USNM 15660, and found in very close proximity to it based on bone impressions, were first investigated by Michael Brett-Surman in 2009. In 2015, he reported that the blocks contained osteoderms, the first confirmation of their existence on Alamosaurus.
   No skull material is known, except for a few slender teeth.
  The restored Alamosaurus skeletal mount at the Perot Museum  (pictured right) was discovered when a member of an excavation team at a nearby sight had to go around a hill to answer nature's call.
caption: Restored Alamosaurus skeletal mount at the Perot Museum.
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