Madrid, 12 (European press)
By analyzing the fossil skulls of animals during the transition from the aquatic environment to the terrestrial environment, researchers from the University of Bristol, Pompeu Fabra University in Barcelona and University College London found that tetrapods have more complex connections between skull bones than fish. Rather than enhancing the diversity of life on Earth, these changes in skull anatomy actually restricted the evolution of tetrapod skulls.
Tetrapods evolved from fish and were the first land animals with their limbs and toes. The ancestors of everything from amphibians to humans.
The research, published in Science Advances, determined the organization of skull bones in more than 100 living and fossil animals to better understand how skulls changed as tetrapods evolved.
Lead author James Rawson, of the Bristol School of Geosciences, said: “Quadrupedal skulls generally contain fewer cranial bones than their fish ancestors, but simply counting the number of bones is missing some important data. A technique called network analysis, where the order of which skull bones that connect are recorded is recorded. It has bones in addition to the number of bones.
Author Dr. Borja Estiv-Altava, an expert in this technique, said: “Traditionally, anatomical research has been primarily descriptive or qualitative. Network analysis provides a powerful mathematical framework for estimating anatomical relationships between bones: a type of data that is often overlooked in most evolutionary studies. morphology”.
The authors found that tetrapods that have fewer skull bones than fish have a more complex skull organization.
“It may seem odd, but having fewer bones means that each of these bones has to connect to more of its neighbors, resulting in a more complex arrangement. Modern frogs and salamanders have the most complex skulls of any other animal,” Rawson added. What has been studied.” The skulls of early tetrapods were also combined into a single unit, while their fish ancestors had skulls made up of several distinct sections.
By looking at a variety of cranial bone arrangements over time, the authors also found that the origin of tetrapods coincides with a decline in a variety of cranial bone arrangements. Professor Emily Rayfield, lead author of the study, said: “We were surprised that these changes in the skull seemed to limit the evolution of tetrapods, rather than promoting radiation in new habitats on Earth. We believe that neck evolution, extinction events or a bottleneck in skull growth may be responsible. .”
“We also see a similar decrease in the structural variability of the limb bones in early tetrapods, but the decline in limbs occurs 10 million years ago. Various factors seem to influence the development of the skull and limbs in early tetrapods.” And we have a lot to learn about this pivotal moment in our evolutionary history.”