This key to the workers of Novomessor is based on Creighton (1950), Umphrey (1996), Mackay and Mackay (2002) and unpublished notes by Bill Mackay.
- Posterior section of head in the form of an elongate neck => Novomessor ensifer
- Posterior section of head broadly convex, never in the form of an elongate neck => 2
- Head (excluding mandibles) slightly longer than broad, usually with wavy, longitudinal or transverse rugae extending almost to posterior border, frons usually granulose; common in arroyos and desert canyons => Novomessor albisetosus
- Head (excluding mandibles) at least 1 ⅓ as long as broad with wavy longitudinal rugae well developed only in anterior half of head; posterior half with feeble rugae which are replaced towards posterior border with fine, coriaceous sculpture; common in open desert => Novomessor cockerelli
- Creighton, W. S. 1950a. The ants of North America. Bulletin of the Museum of Comparative Zoology 104: 1-585.
- Mackay, W.P. & Mackay, E.E. 2002. The Ants of New Mexico: 400 pp. Edwin Mellen Press, Lewiston, N.Y.
- Umphrey, G. J. 1996. Morphometric discrimination among sibling species in the fulva-rudis-texana complex of the ant genus Aphaenogaster (Hymenoptera: Formicidae). Can. J. Zool. 74: 528-559.