Dioon, Lindley, 1843

Gutiérrez-Ortega, José Said, Pérez-Farrera, Miguel Angel, Chemnick, Jeffrey & Gregory, Timothy J., 2021, A reassessment of Dioon merolae (Zamiaceae) leads to the description of Dioon salas-moralesae, a new cycad species from Southeastern Oaxaca, Mexico, Phytotaxa 528 (2), pp. 93-110 : 104-105

Key to the Dioon species in the Purpusii clade

Dioon salas-moralesae , Dioon merolae and Dioon oaxacensis belong to the Purpusii clade, as determined in previous phylogenetic studies ( Gutiérrez-Ortega et al., 2018b, 2018c; Dorsey et al. 2018). The other species in this clade are Dioon argenteum , Dioon califanoi De Luca & Sabato (1979: 170–172) , Dioon caputoi De Luca, Sabato & Vázquez Torres (1980: 44–46) , Dioon holmgrenii (1981b: 552–554), Dioon planifolium , and Dioon purpusii Rose (1909: 260– 261) . A key for the species of the Purpusii clade is here provided.

1a. Leaves green when emerging .............................................................................................................................................................2

1b. Leaves silver when emerging ......................................................................................................................................... D. argenteum

2a. Leaflets strongly curved downward in the apical portion .................................................................................................. D. merolae

2b. Leaflets not or slightly curved downward in the apical portion.........................................................................................................3

3a. Leaflets strongly imbricated...............................................................................................................................................................4 3b. Leaflets not imbricated.......................................................................................................................................................................6

4a. Leaflets inserted obliquely on the rachis, leaf strongly keeled ......................................................................................... D. califanoi

4b. Leaflets not obliquely inserted on the rachis......................................................................................................................................5

5a. Leaflets flat, leaf frequently moderately keeled............................................................................................................ D. oaxacensis

5b. Leaflets slightly curved downward in the apical portion ...................................................................................... D. salas-moralesae

6a. Leaves moderately keeled ................................................................................................................................................. D. purpusii

6b. Leaves not keeled ...............................................................................................................................................................................7

7a. Leaflets 4–5 mm wide, widely spaced along the rachis ...................................................................................................... D. caputoi

7b. Leaflets> 5 mm wide, slightly spaced along the rachis......................................................................................................................8

8a. Leaflets with 3–4 long spines on the upper margin and slightly decurved ................................................................... D. holmgrenii

8b. Leaflets flat with 0–2 long spines on the upper margin ............................................................................................... D. planifolium