They do, however, have a unifying feature, their skull, and in particular their nasal tubes. They are predominantly found in the Southern Ocean with one species, the northern fulmar, ranging in the North Pacific and Atlantic Oceans.
The text describes a group of creatures that share a common anatomical feature: their skulls and particularly their nasal passages. The majority of these animals live in the Southern Ocean, while one species, the northern fulmar, is found in both the North Pacific and Atlantic Oceans.