The muscle study provides new information on

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image: Muscles of the limbs of the Bristol dinosaur, Thecodontosaurus antiquus.
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Credit: Work by Gabriel Ugueto

New research from the University of Bristol has revealed how giant 50-tonne sauropod dinosaurs, like Diplodocus, evolved from much smaller, wolf-like ancestors the size Thecodontosaurus.

In a new study published today in the journal Royal Society Open Science, the researchers present a reconstruction of the muscles of the limbs of Thecodontosaurus, detailing the anatomy of the most important muscles involved in movement.

Thecodontosaurus was a small to medium-sized two-legged dinosaur that roamed what is now the United Kingdom during the Triassic period (about 205 million years ago).

This dinosaur was one of the first to be discovered and named by scientists, in 1836, but it still surprises scientists with new information about how the first dinosaurs lived and evolved.

Antonio Ballell, PhD student at Bristol School of Earth Sciences and lead author of the study, said: “The University of Bristol is home to an enormous collection of beautifully preserved Thecodontosaurus fossils that have been discovered around Bristol. The amazing thing about these fossilized bones is that many retain the scars and rough spots that the limb musculature left on them with its attachment.

These features are extremely valuable in scientific terms for inferring the shape and direction of limb muscles. Reconstructing muscles in extinct species requires this type of exceptional fossil preservation, but also a good understanding of the muscle anatomy of closely related living species.

Antonio Ballell added: “In the case of dinosaurs, we have to look at modern crocodilians and birds, which form a group that we call archosaurs, which means “dominant reptiles”. Dinosaurs are extinct members of this lineage, and due to the evolutionary resemblance we can compare the muscle anatomy of crocodiles and birds and study the scars they leave on the bones to identify and reconstruct the position of these muscles. in dinosaurs.

Professor Emily Rayfield, co-author of the study, said: “These types of muscle reconstructions are fundamental to understanding the functional aspects of the life of extinct organisms. We can use this information to simulate the way these animals walked and ran with tools computers.

Based on the size and orientation of his limb muscles, the authors argue that Thecodontosaurus was quite agile and probably used its forelimbs to grab objects instead of walking.

This contrasts with its later relatives, the giant sauropods, which partly achieved these enormous body sizes by changing to a quadrupedal posture. The muscle anatomy of Thecodontosaurus seems to indicate that the main characteristics of the last dinosaurs of the sauropod line had already evolved in this first species.

Professor Mike Benton, another co-author, said: “From an evolutionary perspective, our study adds more pieces to the puzzle of how locomotion and posture changed during dinosaur evolution and down the line. giant sauropods.

“How were limb muscles changed in the evolution of multi-ton quadrupeds from tiny bipeds? Rebuild limb muscles Thecodontosaurus gives us new insights into the early stages of this important evolutionary transition.

This research was funded by the Natural Environment Research Council (NERC).

Paper:

‘Walking with the first dinosaurs: appendicular myology of the Late Triassic sauropodomorph Thecodontosaurus antiquus by A. Ballell, EJ Rayfield and MJ Benton in Royal Society Open Science.


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