Alamosaurus
AL-uh-moh-SORE-us
- Lived
- 84 to 66 million years ago, Late Cretaceous
- Diet
- Herbivore
- Group
- Sauropods, Saltasauridae
- Found in
- United States
- Named by
- Gilmore 1922
Where its fossils were found
The evidence
Today
75 million years ago
Habitat
Rivers crossed broad floodplains, and rooted tree stumps show broadleaf woodland in the Javelina Formation. Regional neighbors included Tyrannosaurus, Triceratops and Kritosaurus.
Field notes
About Alamosaurus
What it was like
Alamosaurus was an enormous, long-necked plant eater, among the largest dinosaurs known from North America. Its body was carried on thick, pillar-like legs, with a long tail balancing its long neck. Bony plates called osteoderms were embedded in its skin, a feature shared with its close relatives.
Alamosaurus belonged to a group of armored sauropods called titanosaurs, related to Saltasaurus and Opisthocoelicaudia. Exact size estimates vary between studies, but it was almost certainly one of the heaviest animals ever to walk in North America.
Its world
Alamosaurus lived in what is now New Mexico, Texas, and Utah, from about 84 to 66 million years ago, at the very end of the Late Cretaceous. Its bones come from formations including Ojo Alamo, Javelina, Kirtland, North Horn, Black Peaks, and McRae.
It shared its floodplain habitat with the horned Triceratops and Pentaceratops, the duck-billed Kritosaurus and Parasaurolophus, the armored Glyptodontopelta, and the predator Tyrannosaurus.
How it was found
Gilmore named Alamosaurus in 1922, taking the name from the Ojo Alamo Formation where the first fossils were found. About 32 finds of the genus are now known, though sauropods had been mostly absent from North America for tens of millions of years before Alamosaurus reappeared near the end of the Cretaceous.
Field gallery
More views of Alamosaurus
Scenes reconstructed from the available fossil evidence.
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Lived alongside
Found in the same rock formations
A rock formation can hold fossils laid down millions of years apart, so not every animal here met Alamosaurus.
The evidence
The science behind Alamosaurus
Which parts of the picture come from its own bones, and which come from its relatives.
From its own fossils
- Neck vertebrae found joined together show a long neck with complex air spaces inside the bones.
- Limb and shoulder bones show a heavy body supported by sturdy legs.
- Thin slices of its bones show rapid growth in young animals and extensive rebuilding of bone in larger ones.
Borrowed from relatives
- The small head is restored by comparison with better-known titanosaurs such as Rapetosaurus.
- Compact, upright forefeet follow the titanosaur foot plan shared with relatives such as Saltasaurus.
Still unknown
- Its full adult length and weight.
- The precise shape of its skull and the arrangement of any bony skin plates.
- Whether adults cared for their young.
Often drawn wrong
- Its forefeet should be compact weight-bearing pads, rather than spreading fingers with a row of large claws.
Discovery timeline
- 1922Named itGilmore
- 2002Growing upLEHMAN & COULSON
- 2009Growing upWoodward & Lehman
- 2011New findFowler & Sullivan
- 2016Family treeTykoski & Fiorillo
Key papers
The research behind what we know of Alamosaurus
Named it
Named Alamosaurus from shoulder and pelvic bones found in New Mexico, establishing a sauropod in the Late Cretaceous of North America.
A new sauropod dinosaur from the Ojo Alamo Formation of New Mexico. Smithsonian Miscellaneous Collections 72: 1-9
No link available
Growing up
Described a partial young skeleton buried in a shallow floodplain pond, adding previously undescribed bones to the account of Alamosaurus.
A JUVENILE SPECIMEN OF THE SAUROPOD DINOSAUR ALAMOSAURUS SANJUANENSIS FROM THE UPPER CRETACEOUS OF BIG BEND NATIONAL PARK, TEXAS. Journal of Paleontology 76: 156-172
Read the paper : A JUVENILE SPECIMEN OF THE SAUROPOD DINOSAUR ALAMOSAURUS SANJUANENSIS FROM THE UPPER CRETACEOUS OF BIG BEND NATIONAL PARK, TEXAS (opens in a new tab)Growing up
Microscopic bone structure showed fast growth in young animals and extensive bone rebuilding in larger individuals.
Bone histology and microanatomy ofAlamosaurus sanjuanensis(Sauropoda: Titanosauria) from the maastrichtian of Big Bend National Park, Texas. Journal of Vertebrate Paleontology 29: 807-821
Read the paper : Bone histology and microanatomy ofAlamosaurus sanjuanensis(Sauropoda: Titanosauria) from the maastrichtian of Big Bend National Park, Texas (opens in a new tab)New find
Reported huge vertebrae and a partial thigh bone referred to Alamosaurus, suggesting that some individuals grew much larger than familiar skeletons.
The First Giant Titanosaurian Sauropod from the Upper Cretaceous of North America. Acta Palaeontologica Polonica 56: 685-690
Read the paper : The First Giant Titanosaurian Sauropod from the Upper Cretaceous of North America (opens in a new tab)Family tree
Described a connected series of neck bones and used their anatomy to reassess the place of Alamosaurus among titanosaurs.
An articulated cervical series of Alamosaurus sanjuanensis Gilmore, 1922 (Dinosauria, Sauropoda) from Texas: new perspective on the relationships of North America's last giant sauropod. Journal of Systematic Palaeontology 15: 339-364
Read the paper : An articulated cervical series of Alamosaurus sanjuanensis Gilmore, 1922 (Dinosauria, Sauropoda) from Texas: new perspective on the relationships of North America's last giant sauropod (opens in a new tab)
Close relatives
Other members of Saltasauridae
Sources: Wikidata