Amazonsaurus (/ˌæməzənˈsɔːrəs/ AM-ə-zən-SAWR-əs, "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.
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. 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).
Carvalho et al., 2003
Carvalho et al., 2003
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).
Apatosaurinae is the name of a subfamily of diplodocid sauropods that existed between 157 and 150 million years ago in North America. The group includes two genera for certain, Apatosaurus and Brontosaurus, with at least five species. Atlantosaurus and Amphicoelias might also belong to this group.Below is a cladogram of apatosaurinae interrelationships based on Tschopp et al., 2015.Argyrosauridae
Argyrosauridae is a family of large titanosaurian dinosaurs known from the late Cretaceous period of Argentina and Egypt. The group has been recovered as monophyletic, including the type genus Argyrosaurus as well as Paralititan.Baurutitan
Baurutitan is a genus of sauropod dinosaur that lived during the Late Cretaceous in what is now Brazil. The type species, Baurutitan britoi, was described in 2005 by Kellner and colleagues, although the fossil remains had already been discovered in 1957. Baurutitan is classified as a lithostrotian titanosaur, and is distinguished from related genera based on its distinctive caudal vertebrae. This South American dinosaur was found in the Marília Formation near Uberaba, in the Brazilian state of Minas Gerais.Brasilotitan
Brasilotitan is a genus of titanosaurian sauropod dinosaur from the Late Cretaceous (early Maastrichtian) Adamantina Formation of Brazil. The type species is Brasilotitan nemophagus.Cetiosauridae
Cetiosauridae is a family of sauropod dinosaurs. While traditionally a wastebasket taxon containing various unrelated species, some recent studies have found that it may represent a natural clade. Additionally, at least one study has suggested that the mamenchisaurids may represent a sub-group of the cetiosaurids, which would be termed Mamenchisaurinae.Diplodocinae
Diplodocinae is an extinct subfamily of diplodocid sauropods that existed from the Late Jurassic to Early Cretaceous of North America, Europe and South America, about 161.2 to 136.4 million years ago. Genera within the subfamily include Tornieria, Supersaurus, Leinkupal, Galeamopus, Diplodocus, Kaatedocus and Barosaurus.Cladogram of the Diplodocidae after Tschopp, Mateus, and Benson (2015).Eomamenchisaurus
Eomamenchisaurus (meaning "dawn Mamenchisaurus") is a genus of mamenchisaurid sauropod dinosaur from the Middle Jurassic of Yuanmou, Yunnan, China. The type species is E. yuanmouensis, described by Lü Junchang et al. in 2008.Ferganasaurus
Ferganasaurus was a genus of dinosaur first formally described in 2003 by Alifanov and Averianov. The type species is Ferganasaurus verzilini. It was a sauropod similar to Rhoetosaurus. The fossils were discovered in 1966 in Kyrgyzstan from the Balabansai Formation and date to the Callovian stage of the Middle Jurassic.Flagellicaudata
Flagellicaudata is a clade of Dinosauria. It belongs to Sauropoda and includes two families, the Dicraeosauridae and the Diplodocidae.Gravisauria
Gravisauria is a clade of sauropod dinosaurs consisting of some genera, Vulcanodontidae and Eusauropoda.Huangshanlong
Huangshanlong is a genus of mamenchisaurid dinosaurs native to the Anhui province of China. It contains a single species, Huangshanlong anhuiensis. H. anhuiensis represents, along with Anhuilong and Wannanosaurus, one of three dinosaurs fround in Anhui province.Itapeuasaurus
Itapeuasaurus (meaning "Itapeua lizard") is a genus of rebbachisaurid sauropod dinosaur from the Alcântara Formation from Maranhão in Brazil. The type and only species is Itapeuasaurus cajapioensis. It would have been around 10 metres (33 ft) to 15 metres (49 ft) when fully grown.Kaijutitan
Kaijutitan (meaning "Kaiju titan" after the type of Japanese movie monsters) is a genus of basal titanosaur dinosaur from the Sierra Barrosa Formation from Neuquén Province in Argentina. The type and only species is Kaijutitan maui.Pilmatueia
Pilmatueia is a diplodocoid sauropod belonging to the family Dicraeosauridae that lived in Argentina during the Early Cretaceous.Rebbachisauridae
Rebbachisauridae is a family of sauropod dinosaurs known from fragmentary fossil remains from the Cretaceous of South America, Africa, North America, and Europe.Rebbachisaurinae
Rebbachisaurinae is a subfamily within the family Rebbachisauridae, defined to include Rebbachisaurus garasbae and exclude Limaysaurus tessonei. It was first proposed as a rank by Jose Bonaparte in 1995, to include Rebbachisaurus. Some phylogenies however, include Rebbachisaurus in a clade with Limaysaurus, and thus the subfamily was not used. In 2015, a phylogenetic analysis was conducted, and it found Rebbachisaurus instead to be closer to Nigersaurus and related genera than Limaysaurus, and thus was used to replace Nigersaurinae as Rebbachisaurinae is the older term and is named after the genus used for the formation of the family Rebbachisauridae. The 2015 cladogram of Fanti et al. is shown below.Tambatitanis
Tambatitanis is an extinct genus of titanosauriform dinosaur from the Early Cretaceous (probably early Albian) of Japan. It is known from a single type species, Tambatitanis amicitiae. It was probably around 14 meters long and its mass was estimated at some 4 tonnes. It was a basal titanosauriform and possibly belonged to the Euhelopodidae.Tastavinsaurus
Tastavinsaurus is a genus of sauropod dinosaur belonging to the Titanosauriformes. It is based on a partial skeleton from the Early Cretaceous of Spain. The type species is Tastavinsaurus sanzi, named in honor of the Rio Tastavins in Spain and Spanish paleontologist José Luis Sanz.Tengrisaurus
Tengrisaurus (meaning "Tengri lizard") is a genus of lithostrotian sauropod, from the Early Cretaceous (Barremian-Aptian), of the Murtoi Formation, Russia. It was described in 2017 by Averianov & Skutschas. The type species is T. starkovi.