Amargasaurus
This long-necked sauropod features long spines protruding from the back of its neck. It’s known from a nearly complete skeleton, missing only a few bones and most of the skull.
Clade: Dinosauria
Order: Saurischia
Clade: Sauropoda
Family: Dicraeosauridae
Genus: Amargasaurus (“La Amarga Lizard”
Species: A. cazaui
Amargasaurus was a plant eater, and its relatively short neck compared to other sauropods probably meant that they fed on lower-growing plants, so would likely not compete with their larger long-necked relatives.
The purpose of the sail and spines is still considered a mystery, though some scientists have proposed theories. Some believe the spines were a defensive weapon to protect Amargasaurus from predators, like some modern-day antelopes. However, if the spines were indeed covered by a sail, this is less likely. A sail may have been used for display to attract mates, potentially with vibrant patterns or coloration.
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)
Amargasaurus lived during the Early Cretaceous Period, around 130-120 million years ago. It lived alongside other long-necked sauropods in what is now Argentina in South America.
Amargasaurus was named for the La Amarga Formation in Argentina where its bones were discovered. Its remains were uncovered during a 1984 expedition led by a paleontologist named Jose Bonaparte. This fossil-finding journey would also unearth the bones of the meat-eater Carnotaurus, although the rocks they were found in indicate these two dinosaurs were separate by many millions of years.
Guillermo Rougier, a member of the expedition, found what is, to this date, the only known skeleton of Amargasaurus. Like many sauropod remains, the skull was poorly preserved and only the rear portion was found. Its skull is usually reconstructed to resemble its relative, Dicraeosaurus, whose skull is more completely known.
References
Paul, G. (2016). The Princeton Field Guide to Dinosaurs, 2nd Edition. Princeton, New Jersey: University Press Princeton.
https://onlinelibrary.wiley.com/doi/abs/10.1111/joa.13659
https://en.wikipedia.org/wiki/Amargasaurus
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