Amargasaurus grew to around 30 feet long, which was large for most animals, but small for a long-necked sauropod (some of which could grow well over 100 feet long). Other than its size, it was mostly similar to other sauropods in body shape, with a long neck and tail, robust body, and thick legs. However, it had one noteworthy feature that most other sauropods lacked – a long double row of spines protruding from its neck vertebrae.
These spines could reach two feet in length. How exactly they looked in life is not known. It was believed by some scientists that they were covered in a sheath of keratin, like the horns of a bull, while still others believed they supported a sail like the ones seen on animals like Dimetrodon. Still others even proposed that the two rows of spines held an enclosed air sac between them that would be connected to the lungs.
More recently, a detailed analysis of the spines has supported the idea that they were covered in skin that formed a sail, possibly like that of Spinosaurus.
SIZE: 30-33 feet (9-10 meters)
WEIGHT: 2.9 short tons (2.6 metric tons)