Many of the oldest known fossils of these reptiles, which lived 230 million years ago, have been found in the Brazilian state of Rio Grande do Sul, on the border of Argentina
Skull of Buriolestes schultzi, one of the six ancient dinosaur species found in the Santa Maria region
Earlier this year, Brazilian paleontologists found more concrete evidence that dinosaurs may have emerged in South America, by far the most plausible hypothesis based on the fossils currently available, drawing Brazil level in an informal competition that has been dominated by Argentina for more than half a century: each country has now found six ancient species that were among the first dinosaurs to walk the earth. In February 2019, a team coordinated by paleontologist Max Langer, from the University of São Paulo (USP) Ribeirão Preto campus, described a small carnivorous biped, at most 1.5 meters (m) long, that lived 233 million years ago in the area that is now the municipality of Santa Maria in the state of Rio Grande do Sul, about 300 kilometers (km) from the state capital, Porto Alegre.
Nhandumirim waldsangae, the scientific name given to the species and presented to the public in the Journal of Vertebrate Paleontology, was the sixth Brazilian dinosaur fossil found in rocks from the Carnian age, the earliest stage of the Upper Triassic period, which lasted from 237 to 227 million years ago. “We found the fossil while doing field work in a well-known paleontological site in the region in February 2012, when a colleague stepped on a toe bone that was exposed in the rock,” recalls lead author of the scientific paper Júlio Marsola, who studied the new species as part of his PhD, which he defended last year at USP. Brazil and Argentina are the only countries to have found such old fossils that are widely agreed by experts to be dinosaurs.
In addition to the recently discovered Nhandumirim, the other species that compose this primordial sextet are Staurikosaurus pricei, the first dinosaur found in Brazil and described in the scientific literature in 1970; Saturnalia tupiniquim, found by Langer in the late 1990s; and three other species identified in the last decade: Pampadromaeus barberenai, Buriolestes schultzi, and Bagualosaurus agudoensis. Most of them were carnivorous or omnivorous. Only Bagualosaurus, and to a lesser extent, Pampadromaeus, had teeth more suited to a predominantly herbivorous diet.
Illustration of the fauna in Rio Grande do Sul during the Upper Triassic period, when the first dinosaurs lived. 1. A small cynodont, an ancestor of the mammals; 2. Two Bagualosaurus agudoensis dinosaurs; 3. Four other cynodonts of a different species; 4. A rhynchosaur, a herbivorous reptile of the genus Hyperodapedon Jorge Blanco
Compared with their contemporaries in Argentina, the Carnian dinosaurs from the Santa Maria region are still little known, even among paleontologists. “Many of them have been found and described in recent years. In my opinion, they are certainly among the most important recent discoveries to our understanding of the origin and evolution of the dinosaurs,” says American paleontologist Steve Brusatte, from the University of Edinburgh, Scotland. As well as researching the first forms of dinosaurs that appeared on the planet, Brusatte is dedicated to informing the general public about the history of these reptiles. He was the main scientific advisor to the BBC documentary miniseries Walking with Dinosaurs and has written six books on the subject for laypeople. The most recent, Rise and Fall of the Dinosaurs: A New History of a Lost World, was released in Brazil this month.
It is not possible to directly date fossils that are millions of years old, such as dinosaurs and other life forms from the distant past, whose biological tissue has literally turned to stone over time. The situation is very different to that of humans or animals that lived just tens of thousands of years ago. These more recent fossils often still contain collagen, a protein that can be used in carbon 14 dating. The only option for paleontological discoveries as old as dinosaurs is to try to determine the chronology of the rock layer in which they were found, thus deducing their probable age.
The six oldest species of dinosaurs found in Argentina, which historically has been more active in paleontology and has more fossiliferous deposits than Brazil, also lived about 230 million years ago. They all come from the Carnian rocks of the Ischigualasto Formation in the provinces of San Juan and La Rioja, more than a thousand kilometers northwest of Buenos Aires. The best known are Herrerasaurus ischigualastensis and Eoraptor lunensis. The former was a carnivorous biped, first described in 1963, which shared some anatomical similarities with Staurikosaurus, despite being roughly twice the size. The latter was another carnivorous biped, only 1 m long, which was described in 1993 by one of its discoverers, American paleontologist Paul Sereno from the University of Chicago.
Zircon dating “It is impossible to say which of these Brazilian and Argentinian dinosaurs is the oldest,” says Langer, coauthor of the scientific papers that described five of the six found in Carnian rock in Brazil. Last year, Langer published a scientific paper describing how he had dated zircon crystals from Carnian rocks in the Santa Maria Formation, finding a maximum age of 233 million years. This is the most accurate method for establishing the geochronology of rocks as old as the Upper Triassic. “The Carnian rocks of the Santa Maria Formation are 1.5 million years older than those in Ischigualasto, according to zircon dating. But technically, I would say they are more or less the same ages,” explains the USP paleontologist.
The same study also determined the maximum age of the rocks in the Caturrita Formation, which overlies and is sometimes confused with the Santa Maria Formation. The dating indicated that the oldest level of Caturrita rock is 225 million years old, 8 million years less than the oldest Santa Maria strata. A number of interesting fossils have also been found in the Caturrita, such as three specimens of Macrocollum itaquii, a new genus and species of herbivorous dinosaur found in the same section of rock. Described in the scientific literature last year as the earliest record of a long-necked dinosaur, the total length of the reptile is roughly 3.5 m, of which the neck accounts for approximately 1 m.
Infographic Alexandre Affonso
There are also controversial records of other fossils that are older or contemporaneous to the Carnian dinosaurs found in Brazil and Argentina. Extremely fragmented fossils of the reptile Nyasasaurus parringtoni, which lived 243 million years ago according to the Anisian age rocks in which they were found, have been found in Tanzania. Some experts consider the species a dinosaur, but it currently appears to share affinities with almost all classifications.
There are many uncertainties when it comes to classifying early dinosaurs. Until recently, the small Argentine herbivore Pisanosaurusmertii, which lived 228 million years ago, was considered the oldest of the ornithischians, one of the two main branches into which all dinosaurs are divided, characterized by a pelvic structure similar to that of birds. The other branch is the saurischians, whose hips more closely resembled those of lizards. Currently, many consider the Pisanosaurus a silesaurid, one of the closest known relatives of the dinosaurs. Others believe the silesaurids were actually ornithischian dinosaurs. Sacisaurusagudoensis, another small herbivore from Rio Grande do Sul only found in the Caturrita Formation, is also considered a silesaurid. There are also fossils of animals from the northern hemisphere that are difficult to classify and could be predecessors of the first dinosaurs. One example is Saltopus elginensis, a 60-centimeter carnivorous biped that lived about 230 million years ago in what is now Scotland.
In their early days, the dinosaurs were a discrete group of small reptiles, not particularly abundant but positioned as the rulers of the planet. Their image as the pinnacle of grandiosity and ferocity was popularized by fictional films. They arose in a world where most life forms were undergoing a process of major change. Paleontologists agree that dinosaurs emerged a few million years (nobody knows exactly how many) after the earth’s largest-known mass extinction event, which marked the end of the Permian period and the beginning of the Triassic, 252 million years ago.
Toe bone fragments of Nhandumirim waldsangae Átila da Rosa
Probably caused by an abnormal warming of the atmosphere and acidification of the oceans, the cataclysmic event killed about 95% of all marine species and 70% of all land species on the planet. When the first dinosaurs appeared, all of the earth’s continents were united in a single supercontinent known as Pangea, which had an arid climate and many deserts. The northern region is known as Laurasia, and the south Gondwana. What is now South America was connected to present-day Africa and occupied the central-southern area of Gondwana, where the humidity was slightly higher.
Rare fossils During the Triassic period, between 251 and 201 million years ago, the dominant land vertebrates were the archosaurs, a vast group of reptiles from which the dinosaurs, crocodilians, and pterosaurs originated. “Only 5% of the fossils that we find in the Santa Maria Formation are dinosaurs,” explains paleontologist Flávio Pretto, from UFSM’s Paleontological Research Support Center (CAPPA), inaugurated in 2013 and located in São João do Polêsine, right in the center of the 250-kilometer region that comprises the Santa Maria Formation (and the Caturrita). CAPPA’s collection contains about 200 ancient reptile and pre-mammal fossils that have been cataloged but not yet studied. “And we have another 200 or so still waiting to be cataloged,” says Pretto.
An artistic representation of Nhandumirim waldsangae Jorge Blanco
Brazilian paleontology has gained prominence in the search for the planet’s oldest dinosaurs thanks to investments into the formation of quality research teams over the last 20 years, mainly in Rio Grande do Sul but also in other states, and to the increased number of field trips to study Triassic rocks where fossils might potentially be found. For geologist and paleontologist Átila Da-Rosa, from the UFSM central campus in Santa Maria, the Pro-Guaíba project implemented in the early 1990s, sponsored by the Rio Grande do Sul state government with money from the Inter-American Development Bank (IDB) with the aim of studying the environment of the Guaíba River’s hydrological basin, allowed scientists to explore important areas that are home to remote prehistoric sites. “Everything kicked off around this time, mainly thanks to the work being done by paleontologists from the Rio Grande do Sul Zoobotanical Foundation (FZB),” says Da-Rosa.
As well as the researchers from the FZB—which today is at risk of losing its state funding—paleontologists from the Federal University of Rio Grande do Sul (UFRGS), the Pontifical Catholic University of Rio Grande do Sul (PUC-RS), the Lutheran University of Brazil (ULBRA), and institutions from other states, such as USP and the Federal University of Rio de Janeiro (UFRJ), began visiting the area regularly in the last two decades to study and collect fossils from the Santa Maria and Caturrita Formations. The proximity of the UFSM central campus and CAPPA, which is located less than 50 kilometers from the city of Santa Maria, enables quick and easy access to the areas where fossils are most often found in the region.
Rocks at the Janner paleontological site in Agudo, Rio Grande do Sul, where the fossils of two dinosaurs were found: Pampadromaeus barberenai and Bagualosaurus agudoensisPaleontology Lab / USP Ribeirão Preto
CAPPA has three paleontologists (Leonardo Kerber, Rodrigo Temp Müller, and Flávio Pretto), one administrative employee, and a staff car. The team is in charge of monitoring the prehistoric sites in the nine municipalities east of Santa Maria that comprise the area known as Quarta Colônia. “We are half an hour’s drive from most of the sites and we can visit them weekly,” explains Pretto. The center also offers accommodation for up to 10 people, allowing it to host researchers coming to conduct fieldwork in the region. At the geosciences department of the UFSM central campus, paleontologists Átila Da-Rosa and Sérgio Dias-da-Silva lead studies at sites in Santa Maria and neighboring locations to the west of the city.
The UFSM and CAPPA researchers would like to build a museum where they can exhibit the region’s major paleontological discoveries and increase scientific education and awareness. But there seems little chance of the plan becoming a reality in the near future. “Our society does not appreciate as much as it should that we have the oldest dinosaurs in the world here,” says paleontologist Luiz Eduardo Anelli, from the USP Geosciences Institute, who has published 16 books about this group of reptiles and other prehistoric Brazilian animals. “If these fossils had been found in Europe or the USA, they would have already created a ‘park of the earliest dinosaurs’ that would be visited by tourists from countries like ours.”
Project The origin and dispersal of dinosaurs in Gondwana (Neo-Triassic – Neo-Jurassic) (nº 14/03825-3); Principal Investigator Max Langer (USP); Grant Mechanism Thematic Project; Investment R$2,411,452.01.
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