Amazonsaurus
Encyclopedia
Amazonsaurus 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.
Fossil
s 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
epoch
s of the Early Cretaceous
Period, or about 125 to 100 million years ago. Amazonsaurus was recovered in sediments which are interpreted by geologist
s 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 diplodocid
s within Diplodocoidea (Salgado et al., 2004).
, 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).
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of diplodocoid
Diplodocoidea
Diplodocoidea was a superfamily of sauropod dinosaurs, which included some of the longest animals of all time, including slender giants like Supersaurus, Diplodocus, Apatosaurus, and Amphicoelias...
sauropod dinosaur
Dinosaur
Dinosaurs are a diverse group of animals of the clade and superorder Dinosauria. They were the dominant terrestrial vertebrates for over 160 million years, from the late Triassic period until the end of the Cretaceous , when the Cretaceous–Paleogene extinction event led to the extinction of...
from the Early Cretaceous
Cretaceous
The Cretaceous , derived from the Latin "creta" , usually abbreviated K for its German translation Kreide , is a geologic period and system from circa to million years ago. In the geologic timescale, the Cretaceous follows the Jurassic period and is followed by the Paleogene period of the...
Period of what is now South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...
. It would have been a large-bodied quadrupedal herbivore
Herbivore
Herbivores are organisms that are anatomically and physiologically adapted to eat plant-based foods. Herbivory is a form of consumption in which an organism principally eats autotrophs such as plants, algae and photosynthesizing bacteria. More generally, organisms that feed on autotrophs in...
with a long neck and whiplash tail. Although more derived
Derived
In phylogenetics, a derived trait is a trait that is present in an organism, but was absent in the last common ancestor of the group being considered. This may also refer to structures that are not present in an organism, but were present in its ancestors, i.e. traits that have undergone secondary...
diplodocoids were some of the longest animals
Largest organisms
The largest organism found on Earth can be measured using a variety of methods. It could be defined as the largest by volume, mass, height or length. Some organisms group together to form a superorganism, though this cannot truly be classed as one large organism...
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
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
, this is the first named genus from territory in the Amazon Basin
Amazon Basin
The Amazon Basin is the part of South America drained by the Amazon River and its tributaries that drains an area of about , or roughly 40 percent of South America. The basin is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, and Venezuela...
. The generic name is derived from the Brazilian Legal Amazon
Amazônia Legal
Amazônia Legal is the largest socio-geographic division of the South American nation of Brazil, which contains all of its territory in the Amazon Basin...
region and the Greek
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
word sauros ("lizard"). There is one named species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
, (A. maranhensis), which is named after the Brazilian state of Maranhão
Maranhão
Maranhão is a northeastern state of Brazil. To the north lies the Atlantic Ocean. Maranhão is neighbored by the states of Piauí, Tocantins and Pará. The people of Maranhão have a distinctive accent...
. Both genus and species were named in 2003 by Brazilian paleontologists Ismar de Souza Carvalho and Leonardo dos Santos Avilla, and their Argentine
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...
colleague, Leonardo Salgado.
Fossil
Fossil
Fossils are the preserved remains or traces of animals , plants, and other organisms from the remote past...
s of Amazonsaurus, including some back and tail vertebrae, ribs, and fragments of the pelvis
Pelvis
In human anatomy, the pelvis is the lower part of the trunk, between the abdomen and the lower limbs .The pelvis includes several structures:...
, are the only dinosaur remains identifiable at the generic level from the Itapecuru Formation
Itapecuru Formation
The Itapecuru Formation is a geological formation in Brazil whose strata date back to the Early Cretaceous. Dinosaur remains are among the fossils that have been recovered from the formation.-Vertebrate paleofauna:* Theropod indet* Theropod tracks...
of Maranhão. This geologic formation
Geologic formation
A formation or geological formation is the fundamental unit of lithostratigraphy. A formation consists of a certain number of rock strata that have a comparable lithology, facies or other similar properties...
dates back to the Aptian
Aptian
The Aptian is an age in the geologic timescale or a stage in the stratigraphic column. It is a subdivision of the Early or Lower Cretaceous epoch or series and encompasses the time from 125.0 ± 1.0 Ma to 112.0 ± 1.0 Ma , approximately...
through Albian
Albian
The Albian is both an age of the geologic timescale and a stage in the stratigraphic column. It is the youngest or uppermost subdivision of the Early/Lower Cretaceous epoch/series. Its approximate time range is 112.0 ± 1.0 Ma to 99.6 ± 0.9 Ma...
epoch
Geologic time scale
The geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...
s of the Early Cretaceous
Early Cretaceous
The Early Cretaceous or the Lower Cretaceous , is the earlier or lower of the two major divisions of the Cretaceous...
Period, or about 125 to 100 million years ago. Amazonsaurus was recovered in sediments which are interpreted by geologist
Geologist
A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth as well as the processes and history that has shaped it. Geologists usually engage in studying geology. Geologists, studying more of an applied science than a theoretical one, must approach Geology using...
s as floodplain
Floodplain
A floodplain, or flood plain, is a flat or nearly flat land adjacent a stream or river that stretches from the banks of its channel to the base of the enclosing valley walls and experiences flooding during periods of high discharge...
deposits near a river delta
River delta
A delta is a landform that is formed at the mouth of a river where that river flows into an ocean, sea, estuary, lake, reservoir, flat arid area, or another river. Deltas are formed from the deposition of the sediment carried by the river as the flow leaves the mouth of the river...
.
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
Basal (phylogenetics)
In phylogenetics, a basal clade is the earliest clade to branch in a larger clade; it appears at the base of a cladogram.A basal group forms an outgroup to the rest of the clade, such as in the following example:...
diplodocoids. At least one published cladistic analysis shows Amazonsaurus to be more derived than rebbachisaurids, but basal to dicraeosaurids and diplodocid
Diplodocid
Diplodocids, or members of the family Diplodocidae , are a group of sauropod dinosaurs. The family includes some of the longest creatures ever to walk the earth, including Diplodocus and Supersaurus, which may have reached lengths of up to .-Description:While still massive, when compared to the...
s within Diplodocoidea (Salgado et al., 2004).
Biogeography
Basal diplodocoids are found in several parts of South America, as well as northern AfricaAfrica
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
, during the Early Cretaceous, as are titanosaurian sauropods, and the carcharodontosaurid
Carcharodontosauridae
Carcharodontosaurids were a group of carnivorous theropod dinosaurs. In 1931 Ernst Stromer named Carcharodontosauridae as a family, in modern paleontology this name indicates a clade within Carnosauria...
and spinosaurid
Spinosauridae
Spinosauridae is a family of specialised theropod dinosaurs. Members of this family were large, bipedal predators with elongated, crocodile-like skulls, sporting conical teeth with no or only very tiny serrations. The front dentary teeth fanned out, giving the animal a characteristic look...
theropods. By the Late Cretaceous
Late Cretaceous
The Late Cretaceous is the younger of two epochs into which the Cretaceous period is divided in the geologic timescale. Rock strata from this epoch form the Upper Cretaceous series...
Period, the diplodocoids had gone extinct, while titanosaurs proliferated. The predatory theropod families of the Early Cretaceous were also replaced by abelisaurid
Abelisauridae
Abelisauridae is a family of ceratosaurian theropod dinosaurs. Abelisaurids thrived during the Cretaceous Period, on the ancient southern supercontinent of Gondwana, and today their fossil remains are found on the modern continents of Africa and South America, as well as on the Indian...
theropods throughout the southern continents during the Late Cretaceous (Carvalho et al., 2003; Novas et al., 2005).