Dec. 30 () –
A study conducted by researchers at the Museum für Naturkunde in Berlin reveals the evolution of ossification patterns of the vertebral column of quadrupedal vertebrates.
Antoine Verrière and his colleagues succeeded reconstruct the patterns of formation of the bones of the vertebral column in the ancestor of all terrestrial vertebrates drawing on a large dataset of modern vertebrates and fossils with the inclusion of rare new data on the 300-million-year-old reptile Mesosaurus tenuidens. The results are published in Scientific Reports.
The vertebral column is the defining and naming feature of all vertebrates, and its development is generally well understood. However, some crucial aspects of its evolutionary history remain enigmatic. A new study carried out by a team from the Humboldt-Universität zu Berlin and the Museum für Naturkunde in Berlin (Germany) reveals new aspects of this story.
Paleontologist Antoine Verrière, first author of the study conducted as part of his doctoral research, says the project began with exceptionally well-preserved fossils of the reptile Mesosaurus tenuidens. Mesosaurus It was the first reptile that adapted to life in water.. With a long snout and a powerful swimming tail, it inhabited an inland sea in the southern parts of the supercontinent Pangea.
“In some rare juveniles, we observed that the neural arches, the spines that sit on the main part of a vertebra, closed from head to tail as the animals grew, like a zipper. We wanted to know how This pattern fit into the evolutionary history of terrestrial vertebrates, but we quickly realized that very little information was available. So we decided to investigate it ourselves,” he explained. it’s a statement.
The team looked at four of the main patterns of development in the spinal column of amniotes:
– The ossification of the centrum (the main body of a vertebra)
– Ossification of the paired neural arches
– The fusion of the elements of the neural arch initially formed into a vertebral column
– The fusion of the neural arches with the centrum, also called neurocentral fusion.
They used statistical models to chart the evolution of these patterns over the roughly 300 million-year history of terrestrial vertebrates. and thus reconstruct the patterns of the common ancestor of all terrestrial vertebrates.
“What surprised us the most was that these patterns seem to have remained relatively stable over the last 300 million years,” says Prof. Jörg Fröbisch. “Modern and extinct vertebrates are enormously diverse in terms of their body shapes and lifestyles, and the elements of their vertebral columns are organized into complex units that differ greatly between species. However, the ossification patterns were much more conservative than might be expected from the great morphological diversity.”
Although the patterns studied have remained relatively stable throughout evolution, given the enormous time interval considered, some deviations occurred. In particular, birds, mammals, and squamous reptiles evolved their own specific modes of vertebral ossification, which differ from the ancestral condition of amniotes. However, within these groups, the patterns were also surprisingly stable.
“Ostriches and gulls, for example, have very different anatomies and lifestyles, but their vertebral columns ossify in a similar way. This shows that some changes can be observed between the major lineages of terrestrial vertebrates, but within each of the main lineages, spinal development again remained fairly stable“, says Professor Nadia Fröbisch.
“Our study is another great example of how fossil and modern animal data can come together. to get a much deeper picture of the development and evolution of major body structures“, says Antoine Verrière.
