The Alamosaurus was a herbivorous titanosaurian sauropod that lived approximately 105 million years ago during the Upper Cretaceous period in North America. It was one of the last surviving members of its group and is known from a small number of incomplete fossil skeletons. It had a distinctive long neck, small head, and long tail, and its body was partially covered in bony armor.

Key Facts

Alamosaurus pronunciational-ah-moe-sore-us
What does Alamosaurus mean?Ojo Alamo lizard
Dinosaur typeSauropod
On the menuHerbivorous
Length26 meters
Height7.5 meters
Weight35 tons
Life expectancyUnknown
Legs used to get aroundQuadrupedal
Estimated top speedUnknown
When they livedUpper Cretaceous, 105 million years ago
Where they have been found?USA, North America

When & Where

In June 1921, Charles Whitney Gilmore, John Bernard Reeside, and Charles H. Sternberg discovered the first Alamosaurus fossils at the Barrel Springs Arroyo in the Ojo Alamo Formation of New Mexico. Several more Alamosaurus skeletons have since been found in other Maastrichtian formations in Wyoming, Utah, and Texas.

Size & Weight

The Alamosaurus is considered one of the largest sauropods to have lived in North America, matching in size with other titanosaurs such as the Argentinosaurus and Puertasaurus. It was a relatively slender sauropod, with an average length of 26 meters (85 feet) and a weight of 35 tons (39 short tons). Alamosaurus females were likely larger than males, as with many other sauropod species.

Mobility & Diet

The Alamosaurus was a herbivore that likely used its long neck and small head to browse on high vegetation. It walked on all fours but could briefly rear up on its hind legs to reach taller plants. Though no skulls have been found, its teeth have been recovered along with other skeletal remains, and they suggest that this dinosaur had peg-like teeth adapted for eating plants. It may have fed on conifers, ginkgos, ferns, and other plants that grew in the Upper Cretaceous period forests of North America.

Interesting Points

  • The Alamosaurus was one of the last known non-avian dinosaurs, living at the very end of the Cretaceous period.
  • Much debate surrounds the Alamosaurus‘ classification, with some experts considering it a member of the Titanosauria, while others place it within the more basal Saltasauridae.
  • Fossils of a juvenile Alamosaurus have been found in the Ojo Alamo Formation, indicating that this dinosaur reproduced in North America.
  • The Alamosaurus was likely a migratory animal, as its fossils have been found in several different Maastrichtian formations.
  • The fossils are displayed at the Perot Museum of Nature and Science in Dallas, Texas, and the Big Bend National Park in Texas.
  • Alamosaurus was featured in the 1998 documentary film, Walking with Dinosaurs, and in numerous other dinosaur-themed media.

Featured Image Credit: Alamotitan, CC BY-SA 4.0, via Wikimedia Commons