Amargasaurus was a unique, medium-sized member of the Sauropoda, the group of herbivorous dinosaurs known for their long necks and tails. It measured about 9 to 10 meters (30 to 33 feet) in length and weighed approximately 2.6 to 4 metric tons. This dinosaur belonged to the Dicraeosauridae family, a lineage known for having comparatively shorter necks than other sauropods. Its most distinctive feature was the double row of exceptionally tall, elongated bony spines that projected upward from the vertebrae along its neck and back.
Geographical Home
The fossil evidence for Amargasaurus places its existence exclusively in what is now the southern landmass of South America. Its remains were first discovered in the Neuquén Basin, a prolific paleontological region located in Argentine Patagonia. The location is so integral to the dinosaur’s identity that its name, Amargasaurus, translates to “La Amarga lizard.” This name refers directly to the La Amarga Formation, the specific geological unit where the type specimen was unearthed.
Geological Timeline
Amargasaurus lived during the Early Cretaceous epoch. The species existed from roughly 130 to 122 million years ago, spanning the Barremian to the Aptian stages of this epoch. This timing places Amargasaurus far earlier than the more familiar giants of the Late Cretaceous, such as Tyrannosaurus or Triceratops.
The Early Cretaceous world was ecologically different. The presence of Amargasaurus marks a late occurrence of its family, the Dicraeosauridae, which were a key group of sauropods during this time. The fossil record indicates the species was one of the best-known sauropods of its epoch in this region.
Ancient Ecosystem
The environment of the La Amarga Formation during the Early Cretaceous was shaped by an extensive fluvial system, characterized by braided rivers and alluvial plains. Fossil-bearing layers, such as the Puesto Antigual Member, consist mainly of sandstones deposited by these ancient river channels, indicating a dynamic landscape of waterways and shifting sediments. Paleosols, or ancient soils, found within the formation suggest the presence of stable terrestrial areas between periods of flooding.
The climate was likely warm, with seasonal variations, supporting a variety of plant life. The diet of Amargasaurus would have consisted of low-lying vegetation, such as ferns, cycads, and potentially early forms of flowering plants. Studies of its neck vertebrae suggest it habitually fed at a mid-height, keeping its snout around 80 centimeters above the ground.
Amargasaurus shared this habitat with a diverse array of other creatures. The ecosystem included other sauropods, such as the contemporary Amargatitanis and Zapalasaurus, which likely fed on different levels of vegetation to minimize competition. Predatory dinosaurs, including small ceratosaurs like Ligabueino, were also present, along with stegosaurs and crocodylomorphs such as Amargasuchus.