Fossil found in Brazil reveals pterosaurs were covered in colorful feathers |  Energy and Science

Fossil found in Brazil reveals pterosaurs were covered in colorful feathers | Energy and Science

A well-preserved fossil of the crest of a pterosaur that flew over the current region of Chapada do Araripe, in the Northeast 115 million years ago, could change the understanding of the origin and evolution of feathers, structures currently found only in birds and, in the distant past, in the dinosaurs. According to an article published today (20/04) in the scientific journal Nature, the protuberance in the head region of the studied specimen of this extinct winged reptile had two soft tissue covers similar to colored feathers: one small and consisting of a single filament similar to a hair; and a larger one, made up of branched structures, more similar to the feathers of modern birds.

The presence of these feathers or protopfeathers of different shades (impossible to be precise) was identified by a group of European and Brazilian paleontologists from the analysis of the remains of the crest and part of the skull of a pterosaur attributed to the species Tupandactylus imperator. It was a large animal, whose open wings reached an estimated wingspan of 5 meters. The fossil was in the possession of the Royal Belgian Institute of Natural Sciences, in Brussels, and was repatriated to the Museum of Earth Sciences (MCTer), of the Geological Survey of Brazil ‒CPRM, in Rio de Janeiro, in February this year to a friendly way. , without legal proceedings (see table opposite).

The biologist Hebert Bruno Nascimento Campos, of the Maurício de Nassau University Center, in Campina Grande, Paraíba, emphasizes the quality of conservation of the pterosaur Araripe. “The level of conservation of the soft structures is amazing,” says Campos, one of two Brazilians who co-signed the study. The other is paleontologist Edio-Ernst Kischlat, from the Porto Alegre unit of the Geological Survey of Brazil – CPRM.

Using modern electron microscopy techniques, the researchers found two types of melanosomes with different shapes in the soft tissues of the rock-preserved ridge. These organelles carry the pigment melanin, which gives color to the skin and feathers of modern birds and some dinosaurs. One of the forms of organelles has a more rounded geometry; the other is longer and oval.

The researchers identified two types of feather-like structures on the back of the pterosaur’s crest. – Photo: BENTON, MJ, Nature, 2022

The melanosomes have been identified within the picnofibers of the Tupandactylus crest, a type of dense filament typical of pterosaur skin. Some scholars consider pycnofibres to be a coat more similar to the hair of mammals. Others, like the new study team, argue that they are a variant of feathers.

“In today’s birds, the color of feathers is strongly linked to the shape of melanosomes,” said paleontologist Maria McNamara, of University College of Cork (UCC), Ireland, one of the study coordinators, in a statement. “Since the types of pterosaur feathers had different forms of melanosomes, these animals must have had the genetic machinery to control the colors of their feathers. This characteristic shows that coloring was a fundamental characteristic even of the first feathers “.

Pterosaurs were the closest evolutionary group of vertebrates to dinosaurs, from which today’s birds are descended. They were contemporary and practically appeared and disappeared from the Earth at the same time. They coexisted between 235 million and 66 million ago, when both groups became extinct. Since some dinosaurs and pterosaurs would have had colorful feathers, McNamara’s team suggests that these mantle structures have a very ancient origin. Feathers, or something similar to them, would already have been present among the vertebrates from which both dinosaurs and pterosaurs derived, about 250 million years ago.

In the authors’ interpretation of the work, these Tupandactylus feathers or protopfeathers did not help the pterosaurs to fly. It seems a paradox, since pterosaurs were the first vertebrates capable of taking flight, tens of millions of years before birds. The colored feathers (candidate for) from the Araripe fossil were supposed to help them control body temperature and possibly function as a type of visual communication, an extra predicate, to attract reproductive partners.

British paleontologist Michael Benton of the University of Bristol in the UK is convinced that picnofibers are a type of feather. “In every detail they are identical to certain feathers of dinosaurs and birds: their general shape, size, branching, attachment to the skin and because they contain melanosomes,” comments Benton, in an interview with Pesquisa FAPESP. The Bristol researcher was not involved in working with the Araripe fossil, but wrote a comment on the article by McNamara and colleagues for Nature.

A pterosaur specialist, paleontologist Alexander Kellner, director of the National Museum (MN) in Rio de Janeiro, disagrees with Benton. “I don’t want to diminish the importance of this new study. The work uses very modern techniques, leads a very relevant debate on the origin of feathers and was made with quality material from Araripe, one of the main sites in the world with pterosaur fossils, ”reflects Kellner. “But I’m not convinced the melanosomes were inside the feathers.”

The paleontologist MN described, in 1997, the first known specimen of Tupandactylus imperator, the so-called holotype of the species. In 2009, based on a Chinese fossil, he named the typical filaments that usually cover the skin of pterosaurs picnofibre. Kellner states that picnofibers do not have the essential characteristics of feathers, in particular the rachis, the main axis from which a series of branches (the beards) start. “It is also possible that these are not melanosomes and that these structures identified in the article as feathers do not come from the epidermis. [camada mais superficial da pele]but from the dermis [camada mais interna, abaixo da derme]”Says Kellner. “The cut and exposed skin of a pterosaur could generate structures that could be mistaken for pycnofibers. I saw it in a dinosaur specimen. ”

It is not always easy to discern the different structures that make up soft tissue in fossils. Organisms preserved in geological strata are usually flattened, with the body pressed and “stamped” into the rock. This can make it difficult to separate and identify the soft parts of a fossil, such as skin, muscle, and connective tissue.

For at least five decades, paleontologists have debated whether the filaments on pterosaurs’ skin can be considered feathers. This discussion, which has supporters on both sides, gained momentum after the description in 1971 of a small specimen of these winged reptiles found in Kazakhstan, between Central Asia and Eastern Europe. It was a fossil with only two feet of wingspan that unmistakably had body parts covered with filaments. It was no coincidence that the species was called Sordes pilosus, a hairy devil in free translation from Latin.

If it is shown that pterosaur pycnofibers can be considered feathers, and even more colorful, it is possible that these structures on the skin originated long before consensus until now. They may have been a feature of an animal group called Avemetatarsalia, a vertebrate lineage that includes both dinosaurs (and birds) and pterosaurs.

“In this case, the simplest and most economical scenario for the origin of feathers would consist in the appearance of structures equivalent to them, such as picnofibers, only once in the evolutionary process”, comments paleontologist Max Langer, of the University of Sao Paulo. (USP). , Campus Ribeirão Preto. “In the first Avemetatarsalia, perhaps about 250 million years ago, feathers would have appeared that would have transmitted this characteristic to the lineages that later gave rise to dinosaurs and pterosaurs.” It is possible that feathers have appeared more than once in evolutionary history, independently and at different times, in dinosaurs and pterosaurs. But paleontologists like to embrace economic hypotheses, as they assume that the logic of nature is.

The trade allowed the return of the fossil

On Sunday 6 February this year, a diplomatic bag from Brussels, the capital of Belgium, arrived at Rio de Janeiro’s Galeão airport, with five pieces of a rock slab, four larger and one smaller, forming a square of about 60 centimeters per side and for a total of about 20 kilos. The piece featured the crest and parts of the skull of a well-preserved fossil of a pterosaur of the species Tupandactylus imperator, which lived 115 million years ago in present-day Chapada do Araripe, in the division of Ceará, Pernambuco and Piauí.

The material had left Brazil illegally, like other fossils from that region, at an unknown time and ended up in the hands of a private collector in Europe. An agreement signed on 11 October last year between the Brazilian embassy in Brussels and the Royal Belgian Institute of Natural Sciences, in which the fossil was hosted for studies by the institute’s researchers, guaranteed a friendly repatriation, without the need for measures. judicial, gives the game to the country. The fossil is now in the Museum of Earth Sciences (MCTer), of the Geological Survey of Brazil – CPRM, in Rio de Janeiro. “It is on display at the museum in an exhibition of fossils and replicas of Brazilian pterosaurs until May 7,” says Rafael Costa da Silva, curator of the paleontology sector at MCTer.

While studying pterosaur fossils at the Natural History Museum in Karlsruhe, Germany, biologist Hebert Bruno Nascimento Campos saw in 2016 a video presentation on an Araripe pterosaur specimen by paleontologist Aude Cincotta, who was then doing her doctorate. research at the Royal Institute. Belgian natural sciences. “I was interested in the material and asked for permission to see it,” says Campos. He went to Brussels and quickly examined the sample. He later discovered that the fossil, despite being at the institute, belonged to a private collector.

In 2017, he, Cincotta, the German paleontologist Eberhard Frey, curator of the Karlsruhe museum, and two other co-authors presented a brief report on the fossil at a paleontology congress. Subsequently, Campos contacted Brazilian paleontologist Edio-Ernst Kischlat, of the Porto Alegre unit of the Geological Survey of Brazil – CPRM, who initiated an informal negotiation process with the management of the Royal Belgian Institute of Natural Sciences for the return of the fossil. in Brazil . . The official negotiations with the institute ended up being handled by the Ministry of Foreign Affairs and, as attested by the landing of the fossil in February, the agreement was successful. Before the article about Tupandactylus’ apparent colored feathers appeared in Nature, the material was already in Brazil.

The outcome was very different from what happened with another fossil from Araripe, who left the country irregularly. In December 2020, British paleontologist David Martill, of the University of Portsmouth, UK, and other colleagues published an article in the journal Cretaceous Research describing a rare specimen of dinosaur, informally called Ubirajara jubatus, that lived 120 million years ago. . years (see Pesquisa FAPESP n ° 301). The study, which did not convincingly explain the origin of the material, was heavily criticized by Brazilian paleontologists and on social media. Cretaceous Research therefore decided to retract the article, canceling its publication. The dinosaur fossil in question can be found in the Karlsruhe museum. Its curator, Eberhard Frey, incidentally, was one of the co-authors, along with Martill, of the portrayed work. (MP)