Amazonsaurus

Taxobox
name = "Amazonsaurus"
fossil_range = Early Cretaceous


image_width = 200px
image_caption = Reconstruction of "Amazonsaurus maranhensis".
regnum = Animalia
phylum = Chordata
classis = Sauropsida
superordo = Dinosauria
ordo = Saurischia
subordo = Sauropodomorpha
infraordo = Sauropoda
superfamilia = Diplodocoidea
genus = "Amazonsaurus"
species = "A. maranhanensis"
binomial = "Amazonsaurus maranhanensis"
binomial_authority = Carvalho "et al.", 2003

"Amazonsaurus" (pronEng|ˌæməzənˈsɔrəs AM-uh-zahn-SAWR-us; meaning "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.

Despite the fact that other dinosaurs have been found in Brazil, this is the first named genus from territory in the Amazon Basin. The generic name is derived from the Brazilian Legal Amazon region and the Greek word "sauros" ("lizard"). There is one named species, ("A. maranhensis"), which is named after the Brazilian state of Maranhão. Both genus and species were named in 2003 by Brazilian paleontologists Ismar de Souza Carvalho and Leonardo dos Santos Avilla, and their Argentine colleague, Leonardo Salgado.

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. [ [http://www.dinodata.org/index.php?option=com_content&task=view&id=2404&Itemid=75 Itapecuru Fm.] at DinoData] This geologic formation dates back to the Aptian through Albian epochs of the Early Cretaceous Period, 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.

The tall neural spines on the tail vertebrae identify "Amazonsaurus" as a diplodocoid sauropod, but the fragmentary nature of the only known specimen makes it difficult to place "A. maranhensis" more specifically within the superfamily Diplodocoidea. However, some features of these vertebrae suggest it may be a late-surviving member of a line of basal diplodocoids. At least one published cladistic analysis shows "Amazonsaurus" to be more derived than rebbachisaurids, but basal to dicraeosaurids and diplodocids within Diplodocoidea (Salgado "et al.", 2004).

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 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

*Carvalho, I.S., Avilla, L.S., & Salgado, L. 2003. "Amazonsaurus maranhensis" gen. et sp. nov. (Sauropoda, Diplodocoidea) from the Lower Cretaceous (Aptian–Albian) of Brazil. "Cretaceous Research". 24: 697-713.
*Novas, F.E., de Valais, S., Vickers-Rich, P., & Rich, T.H. 2005. A large Cretaceous theropod from Patagonia, Argentina, and the evolution of carcharodontosaurids. "Naturwissenschaften". 92: 226–230.
*Salgado, L., Garrido, A., Cocca, S.E., & Cocca, J.R. 2004. Lower Cretaceous rebbachisaurid sauropods from Cerro Aguada del León (Lohan Cura Formation), Neuquén Province, northwestern Patagonia, Argentina. "Journal of Vertebrate Paleontology" 24(4): 903-912.

Footnotes