Stemec is an extinct genus of Plotopteridae, a family of flightless seabird similar in biology with penguins, but more closely related to modern cormorants.

In 2015, those remains were described by Gary Kaiser, Junya Watanabe and Marji Johns as the new genus and species Stemec suntokum, using as holotype the specimen RBCM.EH2014.032.0001.001, a nearly complete coracoid.

[1] The genus name, Stemec, designate an indefinite long-necked black waterbird in the Coast Salish language native of the area in which the holotype was discovered.

The type species name, suntokum, honours the family name of Leah and Graham Suntok, the discoverers of the holotype.

[1] During the Oligocene of Vancouver Island, Stemec lived alongside the Desmostylian Cornwallius, the Aetiocetid Chonecetus and the Pelagornithid Cyphornis in a shallow marine environment rich in sessile fauna.