This report describes two male specimens of the sand fly species Lutzomyia shannoni (Dyar) (Diptera: Psychodidae: Phlebotominae) collected at Fort Rucker, AL, and Fort Campbell, KY, in dry ice-baited light traps during September 2005. The specimens were observed to have anomalies to the number of spines on the gonostyli. The taxonomic keys of Young and Perkins (Mosq. News 44: 263–285; 1984) use the number of spines on the gonostylus in the first couplet to differentiate two major groupings of North American sand flies. The two anomalous specimens were identified as L. shannoni based on the following criteria: 1) both specimens possess antennal ascoids with long, distinct proximal spurs (a near diagnostic character of L. shannoni in North America), 2) the sequences of the partial cytochrome c oxidase subunit 1 gene from both specimens indicated L. shannoni, and 3) the sequences of the internal transcribed spacer 2 molecular marker from both specimens indicated L. shannoni. The anomalous features are fundamentally different from each other as the Fort Rucker specimen possesses a fifth spine (basally located) on just one gonostylus, whereas the Fort Campbell specimen possesses five spines (extra spines subterminally located) on both gonostyli. Because the gonostyli are part of the external male genitalia, anomalies in the number of spines on the gonostyli may have serious biological consequences, such as reduced reproductive success, for the possessors. These anomalies are of taxonomic interest as the specimens could easily have been misidentified using available morphological keys.