Reptiles That Lived In Trees Help Uncover the Origin of Pterosaurs – 09/12/2020 – Science

The origin of the pterosaurs, the most spectacular flying animals in the history of the earth, has become a little less mysterious. New information about the time when these winged reptiles emerged suggests a close relationship between them and small four-legged friends that ate insects and lived in trees in different regions of the world – including Brazil.

The fossils of such animals, known as camp petids, appeared in the Triassic 237 million years ago, and their characteristics suggest that they would be the “sister group” of pterosaurs – something of the first cousins ​​in paleontological jargon. . That is, while flying reptiles are not directly descended from lager peptides, both groups share a very close common ancestor that should provide important information about how creatures of this type developed the anatomy necessary for flight.

You can find new information on the animal family album in an article in this week’s edition of the journal Nature. The work is signed by an international team of scientists that includes Martín Ezcurra from the Argentine Natural History Museum Bernardino Rivadavia, the Brazilian Max Langer from the USP in Ribeirão Preto and Sergio Cabreira from the Southern Brazilian Paleontology Association.

This is an important advance as the genesis of pterosaurs is still a mystery. His fossils initially appear on rocks that are 220 million years old, practically “finished” – with clearly developed wings and other features essential for flight, without intermediate ancestral forms that could only glide, for example.

As a result, it has been difficult to integrate animals into the broader context of reptilian development, although it was clear that they were, in general, part of the large archosauria group (which still includes crocodiles, dinosaurs, and birds – which actually are), a subgroup of carnivorous dinosaurs – and excludes turtles, snakes, and lizards).

This is where the Lagerpetiden come into play, which like the most primitive pterosaurs were also tiny members (usually less than 1 m) in the Archosauria group. Little known until a few years ago, new discoveries in places like Rio Grande do Sul, Argentina, the United States, and Madagascar brought important information about the skulls, teeth, and forelegs of lager peptides and enabled a detailed comparison with other Archosauria.

At this point, the similarities with the pterosaurs began to fit. Among them, Langer mentions the stretching of the bones of the forearm and hands; Tricuspid teeth (that is, with three protrusions or cusps), ideal for insect consumption; and changes in the brain and auditory canals that are important for balance and accuracy of movement.

In pterosaurs, these brain modifications helped the animals move through the air, but their presence in the lagerpetid “cousins” could be viewed as an initial adaptation to the tree environment, along with the presence of crooked claws that would help the animals climb up Trees.

Biologists often refer to this type of pre-adaptation or exaptation as characteristic – they are of course useful to a species in the conditions in which it currently lives, but they can easily be diverted to other uses as their offspring progresses.

“A small four-legged tree could trigger the flight in a ‘tree down’ scheme [das árvores rumo ao solo]not ground [do chão para cima]. We would then have forest flights and not in open environments to the origin of the pterosaurs, ”explained Langer Folha.

Although the new studies of lager peptides have narrowed the anatomical gap between pterosaurs and other Triassic reptiles, fossils that lie in the details of flight have not yet appeared. By the way, the same thing happens with the development of bats. Is this linked to the fact that they are animals of an enclosed forest, small and with a delicate skeleton, which makes the fossils difficult to obtain?

“It makes sense. Forests are the worst environments for fossilization and they are animals with fragile bones. On the other hand, we have the case of ichthyosaurs, who also “appear ready” but are robust animals from the marine environment, ”Langer muses.

For Taissa Rodrigues, a paleontologist at the Federal University of Espírito Santo and a specialist in pterosaurs, there is also an element of happiness in relation to these types of fossils. The transition from carnivorous dinosaurs to bird flight also took time to be documented. “To clear this up, we had to discover two or three places with exceptional conditions for fossilization,” she muses.

For the researcher, the work is an example of how discoveries in the Triassic changed what we knew about vertebrate history significantly. Rodrigues said the data presented in the nature study will now allow other paleontologists to test the new hypothesis about the relationship of pterosaurs based on information about more fossils in the group.

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