The aquatic Shellark species is native to the planet Nexus. The first settlers to discover the bizarre creatures named them after their most obvious features - the behavior and body shape of a seagoing predator with the protective carapace of an aquatic reptile. They can be found in many different bodies of water on the planet, and are equally at home in freshwater and seawater.
Shellarks are not particularly intelligent and have been known to attack almost anything that wanders into their territory, including - to the chagrin of many a shellark - explosive mines and well-armed Mechari, for example.
Scans of local shellark species indicate they are fiercely territorial. It is believed they are recent transplants to freshwater bodies in Whitevale, meaning this behavior may be a result of an abrupt adaption to a greatly reduced habitat.