Final answer:
Archaeopteryx's features suggest that modern species share a common ancestor, supporting evolutionary theory. Evidence shows that birds evolved from theropod dinosaurs within the Dinosauria clade. Scutellosaurus is an example of thyreophorans that diverged evolutionarily.
Step-by-step explanation:
The fossil of Archaeopteryx provides significant evidence for the aspect of evolutionary theory that modern species share a common ancestor. This is illustrated by its blend of reptilian features and evidence of feathers, which are typically associated with birds. This type of evidence supports the theory that birds evolved from theropod dinosaurs within the clade Dinosauria during the Mesozoic era. Furthermore, the discovery of bird-like dinosaurs and dinosaur-like birds highlights the evolutionary transitions through a concept known as divergent evolution.
For instance, Scutellosaurus and other thyreophorans show traits of evolutionary divergence, which refers to the process where a group from a specific population develops into new species, adapting and evolving into different forms. This diversification happens due to varying environmental pressures and natural selection, leading to a wide variety of adapted species from a common ancestor.