How did dinosaurs with hips evolve? • Earth.com

dinosaurs It arose in the late Triassic period (about 225 million years ago) and dominated the Earth until its mass extinction 66 million years ago. near the end of 19The tenth century, enough dinosaur fossils have been found for scientists to develop a binary classification system based primarily on the shape of dinosaur hip bones: saurischians (lizard hips) versus ornithischians (bird hips).

Although this classification has proven reliable enough for all dinosaur remains to be accurately incorporated into one of the two groups, recent studies have argued that hipped and lizard-tipped dinosaurs likely evolved from a common ancestor, thus questioning the usefulness and reliability of the former. classification. Now, a research team led by Cambridge University and the Federal University of Santa Maria In Brazil, he did a new analysis of the origins of hipped dinosaurs and discovered that they likely evolved from a group of animals known as celesorians, which were first identified two decades ago, and have some features of the Saurischians.

Currently, there is a gap of more than 25 million years in the fossil record, which makes it difficult to determine the origins of the birds. “It appears to have originated with all other dinosaurs in the late Triassic period, but it showed a unique set of features that could not be incorporated into the evolutionary succession of their dinosaur cousins,” said study senior author David Norman, a paleontologist at Cambridge. “It was as if they had suddenly appeared out of nowhere.”

However, according to Professor Norman and colleagues, the discovery of the remains of several late-Triassic dinosaur-like animals called Celsaurians could help fill this gap. While these creatures had long, slender legs and hip bones similar to those of the Saurischians, they had a toothless, beak-like area at the front of their lower jaws not unlike the predatory skeleton found in ornithischians.

Professor Norman said: “The Slysauris gradually modified their anatomy during the late Triassic period, so that they became more like ornithischians.” “We were able to trace this transition through the development of the toothless beak, the evolution of the jagged leaf-shaped teeth typical of those seen in herbivores, alterations in the shoulder bones, changes in the proportions of the pelvic bones, and finally the restructuring of the muscular attachment regions of the legs backgrounds”.

These results indicate that ornithischians emerged in the late Triassic period under the guise of silesaurs that gradually rearranged their anatomy until ornithischians evolved with the onset of the Jurassic. Interestingly, these early ornithologists from the late Triassic period retained the surreal hip build.

“So the early ornithologists are, technically, Sureshnes,” Professor Norman concluded. “From a taxonomic perspective, classifying salsaurs as early ornithologists seems inconsequential. But, from Darwin’s perspective, the unique anatomical characteristics of ornithologists are It was To evolve from somewhere, and where it is better than their closest relatives: their surish cousins! “

The study was published in Journal of Zoology of the Linnian Society.

by Andrei IonescuAnd the Earth.com crew clerk