Amargasaurus cazaui
Amargasaurus was a remarkably small sauropod, roughly nine to ten metres long and weighing somewhere between about 2.6 and 3 tonnes according to the most frequently cited estimates. Its trademark feature was the neck: two parallel rows of greatly elongated spines, formed by split neural spines on the vertebrae, rose from the back of the skull and continued onto the shoulders and forward part of the back.
Amargasaurus
Amargasaurus cazaui
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Weight
2600–3000 kg
Length
9–10 m
Diet
Herbivore
Period
Cretaceous
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2600–3000 kg
9–10 m
Cretaceous
Quadrupedal
2–3 m
20 km/h
Herbivore
2 recorded fossil finds in Argentina. First described in 1991 by Salgado and Bonaparte.
Sites and counts from the Paleobiology Database
The timeline shows the whole age of dinosaurs – and how much time has passed since. The glowing part is when Amargasaurus lived.
million years ago
Lived 129.4–122 million years ago
If the whole age of dinosaurs were a single day, Amargasaurus lived at 16:18.
Chapter • Meet the dinosaur
Amargasaurus was a remarkably small sauropod, roughly nine to ten metres long and weighing somewhere between about 2.6 and 3 tonnes according to the most frequently cited estimates. Its trademark feature was the neck: two parallel rows of greatly elongated spines, formed by split neural spines on the vertebrae, rose from the back of the skull and continued onto the shoulders and forward part of the back. The longest of these neck spines exceeded half a metre. Otherwise the animal followed the standard sauropod blueprint – four pillar-like legs, a barrel-shaped body, and a long tapering tail carried clear of the ground rather than dragged.
Chapter • Where it lived
Amargasaurus lived roughly 129–122 million years ago, in the Barremian and early Aptian stages of the Early Cretaceous. Every known fossil comes from the La Amarga Formation of Neuquén Province in north-western Patagonia, Argentina. Those rocks were laid down on a semi-arid plain crossed by rivers, with temporary lakes, floodplain muds and stretches of windblown sand. Ferns, cycads, ginkgos and conifers dominated the vegetation; flowering plants had not yet taken over. The same beds have produced the small sauropod Zapalasaurus and early theropods, hinting at an ecosystem with several different plant-eating niches.
Chapter • Wild behavior
Cathemeral
Because only one skeleton is known, there is no direct evidence that Amargasaurus lived in herds. Many other sauropods are found in bonebeds containing several individuals and are assumed to have travelled in groups, so the same may well have been true here – but that inference comes from relatives rather than from the animal itself. The striking neck spines are most often read as a social signal: a way of displaying to potential mates, recognising members of the same species, or intimidating predators and rivals. Actual combat with the spines is considered less likely, since the bony cores were fairly slender.
The name means roughly "La Amarga lizard", after the creek and rock formation in Neuquén Province, Argentina, where the skeleton was found.
The species name cazaui honours geologist Luis Cazau, who pointed the palaeontologists towards the fossil-rich beds.
The entire species is known from a single individual, the holotype MACN-N 15, including part of the skull, most of the neck, back, hips and a hind limb.
Amargasaurus was a dwarf among sauropods; several of its relatives were twice as long, and dicraeosaurids as a group had short necks compared with other long-necked dinosaurs.
Researchers still argue whether the spines supported one sail, two separate sails, or were each sheathed in horn like the horns of modern cattle and antelope.
The structure of the neck suggests the head was usually held low, so the animal browsed close to the ground rather than high in the trees.
Amargasaurus lived tens of millions of years after the giant Jurassic sauropods; the La Amarga Formation belongs to the Early Cretaceous.
The fossil was excavated in 1984 on an expedition led by José Bonaparte and formally described in 1991 by Leonardo Salgado and Bonaparte.
Chapter • Scientific place
www.dimensions.com
Reviewed: 9/5/2026
VERIFY:length_max_m: stored=13 suggested=10 confidence=high — Current descriptions of the holotype (MACN-N 15) consistently give a total length of about 9–10 m for Amargasaurus, with the largest published figures around 10.3 m. A stored maximum of 13 m exceeds every estimate the literature supports.
Open sourcewww.tandfonline.com
Reviewed: 9/5/2026
VERIFY:weight_max_kg: stored=5000 suggested=3000 confidence=medium — Mazzetta et al. volumetrically estimated Amargasaurus cazaui at roughly 2.5 tonnes, and subsequent estimates cluster around 2.6–3 tonnes. A 5,000 kg upper bound is close to double the published mass range.
Open sourcePaleobiology Database
Reviewed: 9/5/2026
Documents the accepted classification of the species from Dinosauria through Sauropoda and Diplodocoidea to Dicraeosauridae, citing the original Salgado & Bonaparte (1991) description.
Open sourceGondwana Research (Elsevier)
Reviewed: 9/5/2026
Reviews the sauropod-bearing localities and stratigraphic levels of the La Amarga Formation in Neuquén Province, Argentina — the only known geographic and stratigraphic range of Amargasaurus.
Open sourceCretaceous Research (Elsevier)
Reviewed: 9/5/2026
Documents the geological and depositional setting of the La Amarga Formation in the Neuquén Basin, the Early Cretaceous continental palaeoenvironment in which Amargasaurus lived.
Open sourceJournal of Anatomy (Wiley)
Reviewed: 9/5/2026
Reconstructs the head and neck musculature of Amargasaurus and infers its herbivorous browsing feeding strategy.
Open sourceCretaceous Research (Elsevier)
Reviewed: 9/5/2026
Extinct taxon; conservation status NE
Open sourceNatural History Museum, London
Reviewed: 9/5/2026
Museum overview of Amargasaurus covering its size, age, diet and distinctive twin rows of tall neck spines, used as the basis for the sv, en, da and no description texts.
Open sourceNatural History Museum, London
Reviewed: 9/5/2026
Museum overview of Amargasaurus covering its size, age, diet and distinctive twin rows of tall neck spines, used as the basis for the sv, en, da and no description texts.
Open sourceNatural History Museum, London
Reviewed: 9/5/2026
Museum overview of Amargasaurus covering its size, age, diet and distinctive twin rows of tall neck spines, used as the basis for the sv, en, da and no description texts.
Open sourceNatural History Museum, London
Reviewed: 9/5/2026
Museum overview of Amargasaurus covering its size, age, diet and distinctive twin rows of tall neck spines, used as the basis for the sv, en, da and no description texts.
Open source