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Dinosaurs in the Amazon Rainforest

April 8, 2020

Until relatively recently there was very little evidence for the existence of dinosaurs and other large prehistoric animals in the Americas, and in the Amazon in particular.

It should be remembered that dinosaurs existed during the Mesozoic Era, during the Triassic and Jurassic periods, when the supercontinent Pangaea (Colbert) still existed.

See: Brief history of the Amazon landscape

Dinosaurs became extinct in the Cretaceous, when Gondwana was beginning to separate, the Andes Mountains were beginning to rise, and the Amazon basin did not yet exist.

Guerra-Turín (2011) mentions that there were dinosaurs in the Upper Cretaceous period, at the end of the Cretaceous, in the part where the Central Andes mountain range protruded, and then south of the mountain range.

It was thought that there was little evidence of fossil finds to corroborate the presence of dinosaurs in South America.

However, over time, more and more discoveries have been reported.

Dinosaur fossils found in South America

Salinas, Juárez, Fiorelli (2005) point out that the dinosaurs found in South America since the end of the 19th century correspond to saurischian dinosaurs.

Then, since the end of the 20th century, some ornithischian dinosaurs began to be found, particularly in Argentine Patagonia, which lived there during the Upper Triassic and Upper Jurassic periods.

Heterodontosaurus
Reconstructions of the head, neck and flesh skull of Heterodontosaurus tucki. Source: Tyler Keillor / CC BY

Some pieces of Pisanosaurus and Lesothosaurus were also found in Argentina and Venezuela, and of Heterodontosaurus in Argentina.

Pisanosaurus
Pisanosaurus. Source: FunkMonk (Michael B. H.) / CC BY-SA

Tracks attributable to Hadrosauriformes were also found in Argentina and Bolivia.

Moreno, Blanco, Tomlison (2004) report the discovery of dinosaur footprints that lived in the Upper Jurassic in northern Chile, adding that there is a lack of fossil remains of Jurassic Titanosaurids in South America.

In Central America, specifically in Honduras, in 1971, a femur corresponding to an ornithopod dinosaur, hadrosauroid, was discovered in Camayagua, Honduras (Zúñiga 2019).

Index

Dinosaurs in Brazil

One of the most important finds of dinosaur remains in South America, and confirmation that large saurians inhabited the region that is now the Brazilian Amazon, were those found in the Maranon region of northeastern Brazil in 2003.

It was a sauropod belonging to the family Diplodocoidea, and is related to Diplodocus, which was about 40 m long.

Gnatovorax cabreirai

In the south of Brazil, in Sao Joao de Polesine, researchers from the Federal Universities of Santa Maria and Sao Paulo found the fossil of the Gnatovorax cabreirai, a carnivorous dinosaur that lived about 230 million years ago, in the Triassic, when South America was still part of the supercontinent Pangaea, making it one of the oldest dinosaurs in the world.

Dinosaur fossils found in Brazil
Dinosaur fossils found in Brazil. Study area and sample. (A) Location map of the Marchezan site and surface distribution of geological units in the area. (B) Schematic drawing of CAPPA / UFSM 0009 and associated samples in the rock block prior to final preparation. Silhouette of associated individuals: (C) herrerasaurida; (D) cinodont / 1; (E) rhynchosaur / 1; (F) rhynchosaur / 2 (collected near the rock block); (G) cinodont / 2. Silhouettes not to scale. (H) Reconstructed skeleton of Gnathovorax cabreirai. Source: Gnathovorax cabreirai: a new early dinosaur and the origin and initial radiation of predatory dinosaurs (2019). PeerJ 7:e7963 Author: Cristian Pacheco, Rodrigo T. Müller, Max Langer, Flávio A. Pretto, Leonardo Kerber, Sérgio Dias da Silva(CCbySA4.0)



This dinosaur was a very active predator, with great balance and highly developed vision, and had numerous sharp, serrated teeth and long, powerful claws.

It was almost 3 m long, and is the largest dinosaur found in Brazil (National Geographic 04.12.2019).

Fossils of two more dinosaur species have been found in Brazilian territory.

Buriolestes schultzi

One is the Buriolestes schultzia carnivorous dinosaur measuring 1.5 m, belonging to one of the primitive carnivorous dinosaur families known as Herrerasauridae, which is not known to be an ancestor of the Jurassic and Cretaceous superpredators, such as Tyrannosaurus rex, which devoured other smaller Triassic period saurians, such as the rhinosaurus and the cinodont, which is considered an ancestor of the current mammals .

A size comparison between an average human and a Schultzi specimen from Buriolestes.
A size comparison between an average human and a Schultzi specimen from Buriolestes.
Source: Audrey.m.horn / CC BY-SA
07-11-2016 Buriolestes schultzi - Photos - Luiz Munhoz (61)

Staurikosaurus pricei

The other, found in 1936, is Staurikosaurus pricei, of the Herrerasauridae group, which was a very small and agile carnivorous species.

Dinosaurs in Argentina

Calvo and Bonaparte (1991) noted that in 1987 the remains of a sauropod Titanosauridae were extracted from the Río Limay Formation in the Argentine province of Neuquén, stating that the most numerous and varied records of the Titanosauridae subfamily have been obtained in South America.

Among them, a sauropod Titanosauridae , which represents a primitive clade of that family.

They also indicated that in Gondwana the Titanosaurs dominated, while in Laurasia, in the Late Cretaceous, the ornithischians stood out.

Saurischian and ornithischian fossils found in South America

A few decades later, in 2005, Salinas, Juárez-Vallieri, Fiorelli (2005), with a larger inventory of studied fossils, considered that dinosaur findings in South America since the end of the 19th century correspond to saurischian dinosaurs, while ornithischian dinosaurs were rare towards the end of the 19th century, when some dinosaurs of this group were found in Argentina and Venezuela.

In Bolivia, in addition, footprints attributable to hadrosauriformes, of the ornithopod group, were found.

Bajadasaurus pronuspinax

In Argentina, apart from the Titanosauridae, other dinosaurs of great importance have been discovered, such as Bajadasaurus pronuspinax, found in 2013, which had a fan of giant spines, averaging 1.20 m each, which protruded from its neck and back.

It had about 20 spines, which were projections of bone, probably reinforced with keratin, protruding from the top of the neck vertebrae.

This dinosaur belonged to the group of sauropods, which were herbivores, quadrupeds, of large size.

Amargasaurus

A close relative of this dinosaur was the large spine-bearing Amargasaurus , which lived some 15 to 20 million years later.

Amargasaurus
Proportions of an average human to Amargasaurus. Author: Nobu Tamura CCbySA

Why have so many dinosaur fossils been found in Neuquén?

Many dinosaur species have been found in Argentine Patagonia. And in their territory, especially in Neuquén, they have left their mark.

When the Andes rose, due to the collision of tectonic plates, some 70 million years ago, the mountain range in its emergence lifted territory from the bottom and exposed a large surface.

Then the strong wind eroded it, exposing it even more.

Thus, when walking on the streets of Neuquén, one is walking on material dated to the Cretaceous period.

The dry desert climate of Patagonia helped to preserve the fossils. All this is very different from the soil of the Amazon basin, which is covered with thick vegetation and where it is very difficult to find fossils.

Dinosaur origin thesis

However, hidden there is an interesting history of the evolution of the planet more than 140 million years ago.

Some paleontologists have put forward the thesis that primitive dinosaurs, that is, the first to appear, developed in the Triassic period, when the supercontinent Pangaea still existed.

They argue that these dinosaurs appeared in Pangea, in what is now South America. And then from there they dispersed throughout the supercontinent.

They base their thesis on the fact that the oldest theropod dinosaurs were found there, corresponding to the Late Jurassic about 214 million years ago, and that they are rare.

Indeed, the discovery in 2009 of a theropod on a ranch in New Mexico is combined with an earlier discovery in Argentina of the skeleton of the herrerasaurus, also a theropod, in the 1960s (El País, Madrid, 10.12. 2009).

Bibliography

  • Colbert E.H. 1981. The Jurassic dinosaurs of North America. Amegihiana. A Gondwanan Paleontological Journal, Vol. 22 (1-2). 117-119.
  • Guerra-Turin F.H. 2011. Subdivision of geologic time in the Peruvian Amazon. Ciencia Amazónica Vol 1 (1), 51-58. Iquitos, Peru. PDF
  • Moreno K, Blanco N, Tomlinson A. 2004. New Late Jurassic dinosaur tracks from northern Chile. Amegihiana, 41 (4), 535-544. Buenos Aires. PDF
  • Salinas G.C., Juárez-Valieri R.D., Fiorelli L.E. 2005. Ornithischian dinosaurs of South America and its paleographic importance. Bulletin of Abstracts of the II Latin American Congress on Paleontology of Vertebrates. Rio de Janeiro. PDF
  • Zúñiga L. 2019. The only dinosaur fossil in Central America was discovered in Honduras in 1971. Innovare: Science and Technology Magazine. Vol. 8 (2), 100. Source.
  • National Geographic. Several years.

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