What evolutionary concept describes the acquisition of bird traits independently across several closely related lineages like those in the Yanliao Biota?

Mosaic evolution

The complex and varying phylogenetic placements derived from analyzing *Xiaotingia*'s morphology underscore the non-linear path taken during the evolution toward modern birds. This phenomenon, where a creature exhibits a mixture of ancestral traits alongside derived traits that appear scattered across different lineages, is known as mosaic evolution. For instance, depending on whether researchers emphasize features like the structure of the manual phalanges (hand bones) or dental/cranial characteristics, *Xiaotingia* shifts between clustering near *Archaeopteryx* or aligning with groups like Dromaeosaurids or Troodontids. The study of *Xiaotingia zhengi* from the Yanliao Biota strongly supports the view that the bird blueprint was not acquired through a single event but evolved piecemeal across multiple, closely related feathered theropod groups.