The multigenus approach is based solely on the structure of the male flowers; no other characters could be consistently associated with one genus or another. Four of the genera—"Attalea" (in a narrow sense), "Orbignya", "Maximiliana" and "Scheelea"—correspond to four different types of male flowers found within the genus. However, a few species have flowers that are intermediate between these four types, including "A. colenda" (which Glassman placed in its own genus, "Ynesa") and this has been used as an argument for the single-genus approach. The fact that there are several hybrids between species occur that would be considered different genera under Glassman's five-genus system was also used as an argument for placing them in a single genus. Molecular phylogenetic work by Alan Meerow and colleagues concluded that multi-genus approach did not produce monophyletic groups, but treating "Attalea" as a single genus did.