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Martín Ezcurra, co-author of the report, is a paleontologist at the Vertebrate Paleontology Section of the CONICET-Argentine Museum of Natural Sciences “Bernardino Rivadavia”. He was also the lead author of the 2020 paper that provided evidence that lagerpetids are most closely related to pterosaurs. Since 2012, he has not stopped working on a fossil dataset, which he hopes to finish in 15 years.
“The idea is to have a complete data set of all these reptiles that lived 265 million and 175 million years ago, which is a very important period in the evolution of reptiles,” he told Ars Technica .
When the initial version was published in 2016, the year after he ea Phone Number List rned his PhD, there were 81 fossils represented. In the years since, that number has nearly tripled. The team used this data set to perform a series of analyzes to determine where Venetoraptor fit on the evolutionary tree and how it compared to other dinosaur or pterosaur precursors.
Ezcurra explained that numbers are assigned to each significant aspect of each bone, such as its shape and overall morphology. “With those numbers,” he indicated, “we build a matrix,” which encodes the anatomical structure of each animal. Having these numbers makes it easier to compare new findings with known species. Currently the data set contains 240 species, with 900 characteristics represented by numbers.
“So it's a huge data set. “There are more than 200,000 different observations, all transformed into numbers,” he added. And with this, the researchers built an evolutionary tree. Even on a powerful cluster and using parallelized code, analysis still takes hours to days.
In addition to building evolutionary trees, the data set also allowed researchers to trace the origin and migration of species and their descendants. Ezcurra highlighted that three elements were needed for this: knowing where each species fits on the evolutionary tree, the geographic location as indicated by fossil discoveries, and its place in geological time.
Comparison between the hand of the fossil and that of a human being
The comparison between the fossil's hand and that of a human being gives an idea of its tiny size. COURTESY: JANAÍNA BRAND DILLMANN
Armed with these three pieces of information, the researchers determined that the lagerpetids probably came from South America . The team also discovered that some later members of the lagerpetid family, discovered in North America, were closely linked to early South American lagerpetids. This indicates that, at some point after their origin, they migrated north.
Using other computer analyzes designed by the researchers, the team was able to “quantify the time and number of latitudinal degrees of the globe that [the dinosaurs and lagerpetids] moved at that time.” They determined that the dispersal occurred shortly after the period called the “Carnian Pluvial Episode,” about 235 million years ago, a time of too much global humidity and more abundant rainfall.
The northern and southern portions of Pangea's single landmass were separated by a massive desert. With the end of the Carnian Pluvial Episode, the climate, specifically within the desert, was less extreme, allowing animals to cross into the northern sections of the world.
Ezcurra's data set also made it easier for the team to compare the morphologies of dinosaur and lagerpetid species with each other, creating another matrix, that of “dissimilarity,” which generated “a 'morphospace' that represents all species in a single area” and graphs how different they were from each other. “With that scheme,” Ezcurra highlighted, “we saw that the diversity of these dinosaurs and precursors of pterosaurs was enormous. Actually larger than that of the first dinosaurs, and similar to that of the first pterosaurs. "So we concluded that dinosaurs and pterosaurs originated from a considerably greater pool of diversity than previously thought.
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發表於 2024-3-12 14:31:55
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