Pan-Oceanic Split

Geological / environmental event

When one ocean split into two.

A peculiar feature of Xkoli’xazian life is the seeming genetic distance between certain fauna, even beyond what is to be expected. This suggests that these organisms split very early within the history of life, before continuing to diversify in a manner that is typical of adaptive radiation.
Current thinking as to why is that soon after life evolved, the ocean split apart and the populations became isolated. This is supported by geologic evidence, which shows that, shortly after the planet consolidated, much of the salt water was concentrated into a single body of water.