New research led by the University of Bristol has revealed how 50-tonne sauropod dinosaurs such as Diplodocus evolved from a much smaller ancestor such as the wolf-sized Thecodontosaurus. Come.
The related research report was published in Royal Society Open Science on January 19, 2022. In the report, the researchers show reconstructions of the muscles of the limbs of Helicodontosaurus and detail the anatomy of the most important muscles involved in locomotion.
Helotodon was a small to medium-sized two-legged dinosaur that roamed present-day Britain during the Triassic period (regarding 205 million years ago).
This dinosaur was one of the first dinosaurs ever discovered and named by scientists in 1836, but it still surprised scientists because it provided new information regarding how the earliest dinosaurs lived and evolved.
Antonio Ballell, a PhD student from the University of Bristol’s School of Earth Sciences and lead author of the study, said: “The University of Bristol has a large collection of well-preserved Helotodon fossils from around Bristol. Found. The amazing thing regarding these skeletons is that many of them retain the scars and wrinkles that were left on when the musculature of the limbs was attached.”
At a scientific level, these features are very valuable for inferring the shape and orientation of the muscles of the limbs. Reconstructing the muscles of extinct species requires this exceptionally preserved fossil, but also a good understanding of the muscle anatomy of living, closely related species.
Antonio Ballell pointed out: “In terms of dinosaurs, we have to look at modern crocodiles and birds, which form a group we call protosaurus, which means ‘reigning reptile’. Dinosaurs are the extinction of this lineage. Members, because of the evolutionary similarities, we can compare the muscle anatomy of crocodiles and birds and study the scars they leave on the bones to identify and reconstruct the location 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 life in extinct organisms. We can use this information to simulate computationally how these animals walk and run.”
Judging by the size and orientation of its limb muscles, the authors suggest that Helodon was fairly agile and likely used its forelimbs to grab objects rather than walk.
This is in stark contrast to its later relatives, the giant sauropods, which achieved these enormous body dimensions in part by transitioning to a quadrupedal posture. The muscle anatomy of Helodontosaurus seems to suggest that key features of later long-legged dinosaurs had evolved in this early species.
Another co-author, Professor Mike Benton, said: “From an evolutionary perspective, our study adds more pieces to the puzzle regarding changes in movement and posture during dinosaur evolution and the line up to giant sauropods.” How did the limb muscles change during the evolution from tiny bipeds to multi-ton tetrapods? Reconstructing the limb muscles of Helicodontosaurus gives us new information regarding the early stages of this important evolutionary transition.”
