SYSTEMATICS OF THE GENUS CORYPHANTHA (CACTACEAE) (CHIHUAHUAN DESERT, MEXICO, ESCOBARIA, TAXONOMY, MONOGRAPH)

Coryphantha, a genus of dwarf pincushion cacti, is revised. In the genus as a whole, ninety-two taxa are given formal taxonomic recognition, sixty-seven of them at specific rank; ten of the taxa are new to science. Coryphantha is viewed as consisting of four subgenera: Coryphantha sensu stricto, Escobaria, Protomammillaria, and an unnamed monotypic subgenus newly suggested for Coryphantha gracilis. Subgenus Escobaria is viewed as consisting of at least two sections, one of which (section Pseudocoryphantha) is circumscribed by the universal presence of a newly described anatomical feature, large flat druses of a type absent from the remainder of the tribe Cacteae. A monograph of section Pseudocoryphantha is presented (eighteen taxa, divided between four species).;The putative phylogenetic relationships of the taxa are addressed, with an emphasis on cladistic methodology. Based on analysis of the entire tribe Cacteae, in which Mammillaria is the most important sister-group to Coryphantha and Ferocactus is the next-closest large outgroup, several taxa are excluded from Coryphantha: Neolloydia, Echinomastus, Cumarinia, Ortegocactus, and Acharagma all are treated as valid genera; Acharagma is newly raised to generic rank. Foveolate seeds and fimbriate sepaloid bracts, formerly viewed as synapomorphies linking Escobaria to primitive taxa of Mammillaria rather than to Coryphantha sensu stricto, are re-interpreted as plesiomorphic conditions.