Scientists discover fossil of ‘cousin’ of pterosaur ancestor

A new study has uncovered what the skeleton of the animal considered a “cousin” of the ancestors of pterosaurs, flying reptiles that lived on Earth from the Triassic period to the end of the Cretaceous (from 220 million to about 65 million years ago) looked like.

The fossil in question, named Scleromochlus tayloriwas first described in 1907 by English paleontologist Arthur Smith Woodward, but at the time the researcher considered it to be a primitive dinosaur.

Subsequent studies of the fossil — which has at least seven known skeletons — classified it differently, being considered as a basal archosaur reptile (a group that includes crocodiles and modern birds and their extinct relatives), as well as a basal avemetatarsal (a group that includes, on the one hand, pterosaurs, and on the other, dinosaurs, including birds) and even as an ancestor of dinosaurs.

The new research, published in this Wednesday’s edition (5) of the scientific journal Nature, was done in light of modern techniques of CT microtomography – the same technique used in medical examinations to, for example, see the internal structures and organs of the body. . The technique was crucial in revealing body shapes and bones that were previously unknown or misinterpreted in the past.

Participating in the study were researchers from the National Center of Museums of Scotland, the universities of Birmingham, Bristol and Edinburgh, and the Natural History Museum in London, all in the United Kingdom, from the Department of Geosciences at Virginia Tech, United States, from the University of of Erlangen-Nüremberg, in Germany, and of the Chinese Academy of Sciences, in China.

the skeletons of S. taylori were discovered in limestone rocks in northern Scotland, near the municipality of Elgin, in very thin plates, pressed against the rocky sediment, and difficult to visualize the structures that are inserted in the plate. This meant that most of the bones present were actually represented by the countermold of the same bones—that is, the mark that the bone leaves in the rock, but the bone itself no longer exists. Using these plates as templates, ancient studies of the fossil used resin and other compounds to produce copies of the skeleton, making it possible to study the structures of the organism, but without destroying them.

Some of these interpretations in the past, however, were wrong or did not consider taphonomic components of the fossil in question (i.e., that relate to the post-mortem events of the animal, but before fossilization), explains Paul Barrett, Researcher Emeritus at the Museum of History. Born in London and senior author of the study.

“The so-called ‘Elgin reptiles’ [como originalmente chamados por Woodward] they are not the most pristine, complete or best preserved skeletons, such as those seen on display in museums. The use of computed tomography revolutionized the study of these difficult-to-identify skeletons and made it possible to reproduce a much more detailed and accurate reconstruction of how these animals were in the past”, says the researcher.

Some of these details that have been revealed are the long tail, the front of the upper jaw thin and long (as in many pterosaurs) and the relatively small body in relation to the size of the head (something that in pterosaurs reached even higher levels of growth than in pterosaurs). head), all indicating that the S. taylori is an animal that has characteristics of both primitive pterosaurs and lagerpetids (the sister group of pterosaurs), explains the study’s first author Davide Foffa.

“In addition, the long upper and lower limbs, but without the ‘arms’ being longer than the lower limbs, indicate that this animal probably had a bipedal posture, not a quadrupedal posture, as has been suggested for animals considered to be the ancestors of the pterosaurs,” he says.

For a long time, the origin of these flying reptiles, considered the precursors of flight in vertebrates and until today the largest winged beings that ever existed on Earth, was an unknown for paleontologists. Recent research, including one led by Brazilian scientists, has revealed that small reptiles that lived in trees and ran on two legs were the likely ancestors of the group — the so-called lagerpetids.

“The new research has a reasonable amount of evidence to place the S. taylori both at the base of lagerpetids, as a member of them, and as a sister group [ou ‘primo’ distante] of these with the pterosaurs”, completes Foffa.

Now, the next step in completing the pterosaur “evolution tree” needs a little luck. This is because in the period of about 20 million years that separates the oldest known lagerpetid from the fossils of pterosaurs themselves, with bodies adapted for flight, no fossils considered as intermediate or “missing links” have yet been found.

“The ancestral fossil could be anywhere in the world in rocks dating back 240 to 220 million years, and finding these specimens is the ‘million dollar question,'” says the paleontologist.

For Barrett, the answer to that golden question may be much closer than scientists realize. “It could be that the ancestor is in a drawer in some scientific collection out there. That’s why collections in museums are so important, because it is only through them that we can have access to fossils that are already known and, with the use of techniques innovative, make new discoveries. This is the true progress of science”, he says.