Quercus delgadoana (Fagaceae), a New Species from the Sierra Madre Oriental, Mexico

.  Quercus delgadoana S. Valencia, Nixon & L. M. Kelly (Fagaceae), a new species from the states of Hidalgo, Puebla, and Veracruz in the Sierra Madre Oriental, Mexico, is described and illustrated. We discuss its morphological similarity to Q. eugeniifolia Liebm., Q. sapotifolia Liebm., Q. salicifolia Née, Q. laurina Bonpl., and Q. affinis Scheidw., with which it shares narrowly lanceolate leaves and fasciculate stipitate trichomes in the axils of the secondary veins on the underside of the lamina. A dichotomous key is provided to distinguish these species.