What does the difference between the *Xema* genus and the *Larus* genus imply taxonomically?

That *Xema* is considered phylogenetically distinct enough to warrant its own genus designation.

The decision by ornithologists and systematists to place *Xema sabini* in its own genus, *Xema*, separate from the large *Larus* genus (which includes common gulls), signifies a conclusion about its evolutionary distance. The distinction suggests that the genetic and morphological differences separating *Xema* from its nearest *Larus* relatives are substantial enough to warrant independent genus status. This implies that the evolutionary split occurred earlier and resulted in greater divergence than the differences observed between any two species residing within the *Larus* genus itself.