The discovery of an avian fossil, in the upper Oligocene Sooke Formation rocks on southwestern Vancouver Island, British Columbia, is the first example from Canada of the Plotopteridae, an extinct family that lived in the North Pacific from the late Eocene to the early Miocene. The fossil is a nearly complete, well-preserved coracoid that exhibits the diagnostic features of the family. Stemec suntokum is described as a new genus and species for this family of extinct, wing-propelled diving birds. Coracoids are exceptionally informative bones that lie at the focus of forces acting on the shoulder where they play a major role in avian locomotory biomechanics. The coracoid of Stemec has an unusually narrow, conical shaft that differs fundamentally from the broad, flattened coracoids of other avian groups.

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