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Amargasaurus

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Amargasaurus was a relatively small (10 meters) sauropod that lived in the early Cretaceous period. It was unique because it had two sail-like fins running down it's neck. Amargasaurus is known from an almost complete skeleton (it is missing the front of the skull and the tail). Amargasaurus was found in La Amarga, a canyon in Argentina.

Description

Amargasaurus was a sauropod from the early Cretaceous period. This plant-eater was about 33 feet (10 m) long and weighed roughly 5000 kg. It had two rows of spines growing out along its backbone along its neck, body, and tail. These spines may have had one or two coverings of skin forming a sail.

History

The name Amargasaurus was coined in 1991 by Argentine paleontologists Leonardo Salgado and José Bonaparte,[1] because its fossil remains were found alongside the La Amarga Arroyo in the Neuquén province of Argentina. La Amarga is also the name of a nearby town, as well as the geologic formation the remains were recovered from. The word amarga itself is Spanish for "bitter," while sauros is Greek for "lizard." The one named species (A. cazaui) is named in honor of the man who discovered the site, Dr. Luis Cazau, a geologist with the YPF oil company, which at the time was state-owned.

This site is located in the lower (older) sections of the La Amarga Formation, which dates to the Early Cretaceous Period, or around 130 to 120 million years ago.

Classification

Amargasaurus and Dicraeosaurus are united with the more recently discovered Brachytrachelopan in the family Dicraeosauridae. Dicraeosaurids and diplodocid sauropods are included in a group called Flagellicaudata.[2][3]

Paleobiology

Amargasaurus is known from a relatively complete skeleton from a single individual. This skeleton includes the back of the skull, and all vertebrae of the neck, back, and hips, as well as a bit of the tail. The right side of the shoulder girdle is also known, as are the left forelimb and hind limb, and the left ilium, a bone of the pelvis.

Vertebral spines

The most obvious feature of Amargasaurus' skeleton is the series of tall spines on the neck and back vertebrae. The spines are tallest on the neck, where they are paired in two parallel rows. These rows continue along the back, decreasing in height as they approach the hips. The lower back and hip vertebrae feature only single spines, which are long but much shorter than those of the neck, comparable to other sauropods. These spines may have supported a pair of tall skin sails. Similar sails are seen in the unrelated dinosaurs Spinosaurus and Ouranosaurus, as well as the pelycosaurs Dimetrodon and Edaphosaurus. There are a variety of hypotheses for the function of these such sails, including defense, communication (for mating purposes or for simple species recognition), or temperature regulation.

Gregory Paul argued that parallel neck sails would have reduced neck flexion. Instead, he proposed that, with their circular rather than flat cross-sections, these spines were more likely covered with a horny sheath. He even suggests that they could have been clattered together for a sound display.[4]

Similar spines are found on the presacral vertebrae of Dicraeosaurus from Africa, although not nearly as tall.

Amargasaurus in The Land Before Time

Several are seen as background characters in The Land Before Time X: The Great Longneck Migration.

Gallery

References

  1. Salgado L & Bonaparte JF. (1991). Un nuevo sauropodo Dicraeosauridae, Amargasaurus cazaui gen. et sp. nov., de la Provincia del Neuquén, Argentina. Ameghiniana 28: 333-346. [in Spanish]
  2. Rauhut OWM, Remes K, Fechner R, Cladera G, & Puerta P. (2005). Discovery of a short-necked sauropod dinosaur from the Late Jurassic period of Patagonia. Nature. 435: 670-672.
  3. Taylor MP & Naish D. 2005. The phylogenetic taxonomy of Diplodocoidea (Dinosauria: Sauropoda). PaleoBios. 25(2): 1-7.
  4. Paul, Gregory S. (2000) The Scientific American Book of Dinosaurs, p 94. St. Martin's Press. ISBN 0-312-26226-4.


External links

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