Morphological and anatomical analyses clarify the species definition of Ceratozamia latifolia Miq. (Zamiaceae) and lead to the description of a new species: Ceratozamia reesii Author Vovides, Andrew P. 0000-0002-3779-1374 Red de Biología Evolutiva, Instituto de Ecología, A. C., 91070 Xalapa, Mexico & andrew. vovides @ inecol. mx; https: // orcid. org / 0000 - 0002 - 3779 - 1374 andrew.vovides@inecol.mx Author Pérez-Farrera, Miguel Angel 0000-0002-5329-1505 Laboratorio de Ecología Evolutiva, Herbario Eizi Matuda, Instituto de Ciencias Biológicas, Universidad de Ciencias y Artes de Chiapas, Tuxtla Gutiérrez 29039, Mexico & perezfarreram @ gmail. com; https: // orcid. org / 0000 - 0002 - 5329 - 1505 perezfarreram@gmail.com Author Salinasrodríguez, María Magdalena 0000-0001-7552-7809 Herbario Jerzy Rzedowski, Facultad de Ciencias Naturales, Universidad Autónoma de Querétaro, Querétaro, 76221 Mexico & manesalinas @ outlook. com; https: // orcid. org / 0000 - 0001 - 7552 - 7809 manesalinas@outlook.com Author Galicia, Sonia 0000-0001-8483-9505 Red de Biología Evolutiva, Instituto de Ecología, A. C., 91070 Xalapa, Mexico & sonia. galicia @ inecol. mx; https: // orcid. org / 0000 - 0001 - 8483 - 9505 sonia.galicia@inecol.mx Author Díaz-Jiménez, Pedro 0000-0003-2079-674X Jardín Botánico Araceario Thomas B. Croat, s / n, Comalcalco 86650, Mexico & aroid 764 @ hotmail. com; https: // orcid. org / 0000 - 0003 - 2079 - 674 X aroid764@hotmail.com Author Calonje, Michael 0000-0001-9650-3136 Montgomery Botanical Center, Coral Gables, FL 33156, USA & michaelc @ montgomerybotanical. org; https: // orcid. org / 0000 - 0001 - 9650 - 3136 michaelc@montgomerybotanical.org Author Gutiérrez-Ortega, José Said 0000-0003-4342-6215 RIKEN Interdisciplinary Theoretical and Mathematical Sciences, Wako, Saitama 351 - 0198, Japan & jose. go @ riken. jp; https: // orcid. org / 0000 - 0003 - 4342 - 6215 jose.go@riken.jp text Phytotaxa 2022 2022-12-13 575 3 224 252 http://dx.doi.org/10.11646/phytotaxa.575.3.2 journal article 10.11646/phytotaxa.575.3.2 dadfba5b-40cf-425b-a24a-13ee8fb37309 1179-3163 7431194 Ceratozamia reesii Vovides, Pérez-Farrera and Gutiérrez-Ortega sp. nov. ( Fig. 14–17 ) Ceratozamia reesii can be distinguished from other species in the genus by having 4–12 leaves per crown, light green color in emerging leaves, petioles armed with thin prickles, leaflets coriaceous, elliptic to lanceolate or oblanceolate, 11–23 pairs. Megastrobilus solitary erect, brown, peduncle 4.2–6 cm long. Seed 2–2.8 cm long. Holotype . MEXICO , San Luis Potosí : Xilitla , Camino a San Pedro Huiztquilico , 790 m a.s.l. , 31 July 2021 , M.A. Pérez-Farrera , P. Díaz , & M.M. Salinas 4017 ♀ (HEM). Isotype : XAL. Plant rupicolous, unbranching, stem short, cylindrical, erect, covered with persistent leaf bases, 12–33 cm tall, 10.5–17 cm in diameter. Cataphylls persistent, brown and densely tomentose at emergence, triangular apex acuminate. Leaves pinnate, 4–12 per crown, forming a semi-open crown, erect, ascending, olive green, 69.5–201 cm long, 39.6–71 cm wide, light green color at emergence, turning olive green at maturity. Petiole terete, 34–67.8 cm long, armed with thin prickles. Rachis green, terete, 34.5–138 cm long, erect, with sparse prickles diminishing into the distal end of the rachis. Leaflets 11–23 pairs, linear, long oblanceolate or oblanceolate, coriaceous, alternate to sub-alternate in the basal part of the leaf, subopposite in the median part, opposite in the apical part, subfalcate into apical part of leaflet, margin entire, apex acute to acuminate, asymmetric; base broad attenuate, articulation yellow adaxially, light green abaxially, 0.4–1.3 cm wide, veins 28–37, parallel, inconspicuous; median leaflets 19.8–35.5 cm long, 1.5– 5.1 cm wide, spaced 1.2–7.2 cm between leaflets. Microstrobilus solitary, conical, erect, light brown when mature, 33–35 cm long, 4.8–5 cm diameter, peduncle densely tomentose, light brown, 14–15 cm long, 1.5–1.8 cm diameter. Microsporophyll cuneiform, 10.11–12.59 mm long, 4.69–6.25 mm wide, distal face bicornate, with light brown color at the central portion, sporangia zone on abaxial surface 4.10–7.65 mm long, microsporangia grouped in 3–4 per sorus. Megastrobilus solitary, cylindrical, erect, 16–16.3 cm long, 6.5–8 cm diameter; apex mucronate, brown pubescent at mature, peduncle short, brown, tomentose, 4.2–6 cm long, 1.06–1.56 cm in diameter. Megasporophylls peltate, bicornate, 3.7–4.2 cm wide, 1.5–2.1 cm tall, distal face pubescent, when mature, distal face presents a light brown to brown color at the central portion, which fades to brown-reddish towards the margins. Seed ovoid, sarcotesta cream when immature, sclerotesta beige when mature, 1.45–1.67 cm diameter, 2.0– 2.28 cm long, with micropylar ridges. Specimens examined : MEXICO . San Luis Potosí : Xilitla , Las Pozas , Jardín Escultórico Edward James , 665 m , 24 April 2018 , M.A. Pérez-Farrera 4021 ( HEM ) ; Xilitla , El Cañón , 580 m , 30 July 2021 , M.A. Pérez-Farrera , P. Díaz , & M.M. Salinas 4016 ( HEM ) ; Xilitla , Cerro de la Silleta , 1300 m , 20 July 2021 , M.M. Salinas s.n. ( QMEX ) ; Cultivated at Jardín Botánico Francisco Javier Clavijero (Veracruz), accession 2001-110A, originally collected by S. Avendaño 5304 at Cerro del Muerto , Xilitla , 25 August 2014 , A.P. Vovides 1522 ( XAL ) . Etymology : The specific epithet was chosen to honor the memory of John David Rees (1932–2021), an American botanist and a mentor on cycads to the principal author. His guidance and knowledge on Mexican cycads were invaluable to the later creation of the Mexican National Cycad Collection of the Francisco Javier Clavijero Botanic Garden of INECOL, Xalapa, Veracruz .