About
Amargasaurus was a distinctive dinosaur that roamed what is now Argentina during the Early Cretaceous period, approximately 129 to 122 million years ago. Though relatively small for a sauropod at around 9 to 13 meters long, it made up for its modest size with one of the most striking anatomical features ever seen in the dinosaur world: two parallel rows of extraordinarily tall running along its neck and back.
These remarkable spines, which were tallest along the neck and gradually decreased in height toward the tail, have sparked considerable scientific debate. Some researchers initially proposed they supported a sheath and stood as individual spike-like projections. However, the currently favored hypothesis suggests they formed a framework for a skin or paired sails. Whatever their exact form, these structures likely served multiple purposes — from species recognition and during mating rituals to or even defense against predators.
The only known skeleton of Amargasaurus was discovered in 1984 by Argentine paleontologist José Bonaparte and his team in the La Amarga Formation of Neuquén Province, Argentina. The remarkably complete specimen, including skull material, was formally described in 1991 by Leonardo Salgado and José Bonaparte. The genus name honors the La Amarga Arroyo where it was found, while the species name cazaui pays tribute to Luis Cazau, a geologist who contributed to the expedition.
As a member of the Dicraeosauridae family, Amargasaurus had a relatively short neck compared to many of its sauropod cousins — a characteristic of this group that may have allowed them to specialize in different feeding strategies than the towering diplodocids and brachiosaurs they lived alongside. This smaller, more compact body plan, combined with its spectacular spines, makes Amargasaurus one of the most unusual and instantly recognizable dinosaurs of the Cretaceous period.
Explore the anatomy
5 featuresTwo parallel rows of tall, bony spikes ran along the neck and back — a feature no other sauropod had. These spines split into pairs from a shared base, giving Amargasaurus its unmistakable double-sail shape that makes it instantly recognisable among long-necked dinosaurs.
Did those dramatic spines hold up a stretchy skin sail, or did they stick out like giant bony spikes covered in horn? Scientists are still arguing about it! The sail idea is winning for now, because the bones don't show the extra reinforcement you'd expect if they had to support heavy horn sheaths standing alone.
Forget those classic super-long-necked dinosaurs — Amargasaurus had a surprisingly short neck for a sauropod. This meant it probably munched on low and mid-level plants instead of treetops, avoiding competition with the towering giants that shared its Early Cretaceous world.
At about 10 metres long, Amargasaurus wasn't huge, but it had thick, pillar-like legs built for strength rather than speed. Computer models of its leg bones suggest it walked slowly and steadily across the dry floodplains it called home.
Only bits of the skull were found, but they hint at a long, low head with skinny, peg-shaped teeth. Teeth like these were perfect for stripping soft plants like ferns and cycads — not for chomping tough, woody stuff.
Where fossils were found
La Amarga Formation
Neuquén · Argentina
125.8–121.4 million years ago(4.4m year span)
Where Amargasaurus Roamed
During the Early Cretaceous, Amargasaurus roamed the floodplains and river valleys of what is now Patagonia, Argentina—then part of the fragmenting supercontinent Gondwana—where a warm, semi-arid climate supported fern prairies and scattered conifer woodlands along meandering waterways.
Keep exploring the vault
Diplodocus
Diplodocus carnegii
Both Amargasaurus and Diplodocus are diplodocoid sauropods that evolved elongated cervical vertebrae with bifurcated neural spines, though Amargasaurus took this to an extreme with its dramatically elongated paired spines forming sail-like structures.
Nigersaurus
Nigersaurus taqueti
Both are diplodocoid sauropods (Amargasaurus in Dicraeosauridae, Nigersaurus in Rebbachisauridae) that evolved specialized feeding adaptations for low browsing.
Saltasaurus
Saltasaurus loricatus
Both are South American sauropods that evolved defensive structures — Amargasaurus with its elongated neck spines possibly serving as defense or display, and Saltasaurus with dermal armor (osteoderms).
Kentrosaurus
Kentrosaurus aethiopicus
Both evolved paired elongated spines along the vertebral column — Amargasaurus on its cervical vertebrae and Kentrosaurus along its back and tail.
Carnotaurus
Carnotaurus sastrei
Both are distinctive South American dinosaurs, though separated by significant time (Amargasaurus Early Cretaceous, Carnotaurus Late Cretaceous).