A norsehlat was an animal native to planet Vulcan, similar to a Terran wolf.

Amongst the Vulcans, it was said that norsehlat had no conception of right or wrong, yet the Vulcans did not allow them to eat their citizens. (TOS novel: Federation)

In 2373, the Klingon nurses of Bendii syndrome sufferer Tarok threatened to feed Ambassador Spock and his aide Srell to the norsehlat if they did not treat their charge with care. (TOS novel: Avenger)

The name would suggest some similarity between the norsehlat and the sehlat, though this is never made explicit.