Amargasaurus (Amarga lizard)
Leonardo Salgado & José Bonaparte - 1991
Estimated 10 meters long
A. cazaui (type)
Argentina, Neuquén province - La Amarga Formation
Early Cretaceous, 132-127 million years ago
Amargasaurus (/@,ma:rg@’so:r@s(also known as “La Amarga lizard”) is a sauropod dinosaur from early in the Early Cretaceous epoch (129.4-122.46 mya) of the present-day Argentina.
It is a single species that is known to exist, Amargasaurus cazaui, and is classified as belonging to the family Dicraeosauridae. It measured 9-10 metres (30-33 feet) in length and had two rows of long spines running across its back and neck that were higher than those of any other sauropod known.
It lived in a shared habitat with at least three sauropod generathat and likely ate at a mid-height, with its snout 80 centimeters (31 inches) above the ground and an average in height 2.7 metres (8.9 feet). Amargasaurus was a sauropod of the Dicraeosauridae, measuring 9-10 metres (30-33 feet) in length and weighing 2.6 tonnes (2.9 small tons).
It exhibited the standard sauropod body structure, featuring neck and tail that were long with a smaller head and a barrel-shaped trunk supported by four legs. Its neck was longer than the majority of sauropods, with a length of 2.4 metres (7.9 feet).
The neck comprised thirteen cervical vertebrae, the opisthocoelous (convex towards both ends and hollow in the back) creating a ball-and-socket joint with vertebrae that were adjacent. The trunk consisted of nine dorsal and likely five sacral vertebrae fused. Dorsal vertebrae of Amargasaurus were devoid of pleurocoels, indicating a robustly developed rib cage.
Amargasaurus was a large sauropod with up-projecting neural spines that surrounded the neck and anterior dorsal vertebrae. The spines were concentric in cross-section and tapered towards the edges, reaching a height of 60 centimeters (24 inches) at the cervical 8th. An elongated similar neural spine was discovered within the neck of the similar Bajadasaurus in 2019, which was bent forward and expanded towards the ends. In the pelvic area, it was large, as evident from the length of the transverse processes that project laterally.
The forelimbs were slightly smaller than the hind limbs, and the majority of the foot and hand bones weren’t preserved. Amargasaurus probably had five digits each, as is the case with all sauropods.
The rear portion of the skull of Dicraeosaurus has been preserved, showing a horselike broad snout with teeth that resembled pencils. The outer nasalis (nostril opening) was located diagonally over the orbit and was large by proportion. It was equipped with three other entrances (fenestrae).
The infratemporal fenestrathat was located beneath the orbital fenestra, was lengthy and narrow, and was visible when looking at the skull through the side. A unique feature was the tiny fontanelles or parietal openings, which are typically seen in young animals and will shrink as an individual matures.
Skull features shared with other sauropods include frontal bone fusions, as well as the particularly long basipterygoid process bones that connect the braincase and the palate. The sole skeleton that is known (specimen ID MACN-N15) was found during February 1984 by Argentine paleontologist Jose Bonaparte. The eighth mission part of the research project “Jurassic and Cretaceous Terrestrial Vertebrates of South America” revealed the complete skeleton of the Horned Theropod Carnotaurus.
The skeleton is derived from sedimentary rocks from the La Amarga Formation, which is believed to date back to the Barremian through the early Aptian phases in The Early Cretaceous, or around 130-120 million years ago.
The skull is the second skull to be identified as belonging to the Dicraeosauridae, and the vertebral column of both the spine and the neck comprised of articulated 22 vertebrae was discovered connected to the sacrum and the skull.