Disentangling the identity of Zamia from Mexican Pacific seaboard, with a description of a new species

We present a revision based on qualitative and quantitative morphological comparisons including all populations of Zamia from the coastal plain of Pacific Mexico. We recognize four species in this area: Z. paucijuga, Z. herrerae, Z. spartea and the new species Z. stenophyllidia which is described from Michoacán, Mexico. Zamia stenophyllidia has is distinct with respect to both vegetative and reproductive structures; namely, linear, lanceolate, papyraceous and narrow leaflets (up to 0.8 cm wide), robust and short prickles (up to 2 mm), and ovoid, yellowish, ovulate strobili. The description of this species implies a recircumscription of Z. paucijuga; on this basis, an epitype for Z. paucijuga is designated here. We also introduce a key for all species of Zamia from Mexico. Biogeographically, the new species is interesting for its sympatry with Dioon stevensonii, a species that has been a model for the study of the formation of modern Neotropical forests.