Amazonsaurus

Amazonsaurus ( , 'Amazon lizard') is a genus of diplodocoid sauropod dinosaur from the Early Cretaceous Period of what is now South America. It would have been a large-bodied quadrupedal herbivore with a long neck and whiplash tail. Although more derived diplodocoids were some of the longest animals ever to exist, Amazonsaurus was probably not more than 12 meters (40 ft) long. Gregory S. Paul estimated in 2010 its weight at 5000 kg. Fossils of Amazonsaurus, including some back and tail vertebrae, ribs, and fragments of the pelvis, are the only dinosaur remains identifiable at the generic level from the Itapecuru Formation of Maranhão. This geologic formation dates back to the Aptian through Albian epochs of the Early Cretaceous, or about 125 to 100 million years ago. Amazonsaurus was recovered in sediments which are interpreted by geologists as floodplain deposits near a river delta.

Amazonsaurus ( , 'Amazon lizard') is a genus of diplodocoid sauropod dinosaur from the Early Cretaceous Period of what is now South America. It would have been a large-bodied quadrupedal herbivore with a long neck and whiplash tail. Although more derived diplodocoids were some of the longest animals ever to exist, Amazonsaurus was probably not more than 12 meters (40 ft) long. Gregory S. Paul estimated in 2010 its weight at 5000 kg. Fossils of Amazonsaurus, including some back and tail vertebrae, ribs, and fragments of the pelvis, are the only dinosaur remains identifiable at the generic level from the Itapecuru Formation of Maranhão. This geologic formation dates back to the Aptian through Albian epochs of the Early Cretaceous, or about 125 to 100 million years ago. Amazonsaurus was recovered in sediments which are interpreted by geologists as floodplain deposits near a river delta. ==Description== Amazonsaurus was a relatively small sauropod, with Brazilian professor Elver Luiz Mayer estimating it to be around in length, while American paleontologist Gregory S. Paul placed it at long and in mass. This makes it relatively small for a rebbachisaurid, as some genera like Rebbachisaurus as large as in length. Caudal vertebrae from both the anterior (front) and distal (away from body) sections of the tail were unearthed. Unlike other rebbachisaurids, the (large extensions from the tops of vertebrae) on the caudal vertebrae are straight and posteriorly (towards the back) inclined. This spine is oriented at a 45 degree angle and is set up at around the middle of the (the body of the vertebra). Additionally, the lateral (side) laminae composed of the (connecting the neural spine and ) and (between the and ) (bony ridges that divide pneumatic chambers) create an anteriorly-oriented bend that makes the anterior surface of the lamina concave whereas the posterior surface is convex, another trait unique to Amazonsaurus. In contrast to the laminae of Limaysaurus, Amazonsaurus ' laminae have a consistent thickness from the base of the neural spines to their apexes. At the posterior ends of the vertebrae are the prezygapophyses, which run almost parallel to the axial plane of the vertebrae while the neural canal opens below the prezygapophyses. The caudal neural arches are extremely tall, typical of diplodocoids. Its dorsal vertebrae bear slightly (convex front and concave back ends), wide, and low centra. These centra have flat ventral (bottom) sides, creating a squared shape. On the lateral (side) faces are deep (large that bore air sacs) which take up most of the internal space of the sides of the centra. As for the dorsal neural spines, they bear axially developed prespinal (before neural spine) laminae. The chevrons are distinct in their open haemal canals and relatively elongated, laterally thin shafts. They are L-shaped overall with a posterior distal process, unlike those of Limaysaurus. The pelvis is only represented by fragments from the proximal (towards body) and mid-sections of the pubis as well as the left ilium. Although lacking the aceptabular surface (the area where the femur articulates with the pelvis), an enlarged obturator foramen and broad, oar-shaped were recovered. Overall, the ilium is transversely (left-to-right) wide, high, and bears pneumatic (air-bearing) adaptations. ==Biogeography== Basal diplodocoids are found in several parts of South America, as well as northern Africa, during the Early Cretaceous, as are titanosaurian sauropods, and the carcharodontosaurid and spinosaurid theropods. By the Late Cretaceous Period, the diplodocoids had gone extinct, while Angolatitan remained and titanosaurs proliferated. The predatory theropod families of the Early Cretaceous were also replaced by abelisaurid theropods throughout the southern continents during the Late Cretaceous (Carvalho et al., 2003; Novas et al., 2005). ==References==

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