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Issue: Vol. 738 No. 1: 22 Jan. 2026
Type: Monograph
Published: 2026-01-22
DOI: 10.11646/phytotaxa.738.1.1
Page range: 1-335
Abstract views: 89
PDF downloaded: 3

Critical review of morphological trait assessment in cycad (Cycadophyta: Cycadales) taxonomy: Importance of consistency and need for standardization

Fairchild Tropical Botanic Garden, 10901 Old Cutler Rd., Coral Gables, Florida, 33156 U.S.A.
Gross morphology qualitative traits quantitative traits taxonomic standards Gymnosperms

Abstract

Taxonomic treatments within the Cycadales are largely based on gross morphological traits. Inconsistent trait assessment can adversely affect the understanding of species and relationships among them. It can also have long-lasting and broad-ranging implications in other areas of study. The objective of this review was to critically evaluate and quantify gross morphological trait assessment consistency in cycad taxonomic descriptions. Follow-up objectives were, if necessary, to determine which factors continue to affect trait assessment consistency and develop protocols to improve consistency in future works. Critical comparisons of accepted name protologues, synonym protologues, and emended, revised, and recharacterized taxonomic treatments revealed a surprisingly low level of consistency in the assessment of qualitative and quantitative traits, resulting from such things as inclusion of data from immature and/or juvenile plants, immature leaves, and/or immature/aberrant cones; differential/inadequate understanding of the shape of diagnostic structures and/or the terms used to describe them; and incomplete/inadequate assessment of variability within and/or among populations. Protocols developed herein to improve morphological trait assessment consistency include capturing the full range of variability for every trait assessed, understanding and using established terms to describe and evaluate traits and character states, standardizing terms for key traits and character states, and not including as diagnostic traits that are variable within or among populations of the same species, vegetative data from immature or juvenile plants, or reproductive data from smaller-than-normal or aberrant cones.

References

  1. Avendaño, S., Vovides, A.P. & Castillo-Campos, G. (2003) A new species of Ceratozamia (Zamiaceae, Cycadales) from Veracruz, Mexico. Botanical Journal of the Linnean Society 141: 395–398.
  2. Bamps, P. & Lisowski, S. (1990) A new species of Encephalartos (Zamiaceae) from northeastern Zaire. Memoirs of the New York Botanical Garden 57: 152–155.
  3. Beentje, H. (2020) The Kew Plant Glossary: An Illustrated Dictionary of Plant Terms, 2nd edition. Kew Publishing, Richmond, Surry, UK, 184 pp.
  4. Brummitt, R.K. & Powell, C.E. (1992) Authors of Plant Names Standard. International Working Group on Taxonomic Databases (TDWG). Available from: http://www.tdwg.org/standards/101 (accessed 25 October 2023).
  5. Calonje, M., Stevenson, D.W. & Osborne, R. (2025) The World List of Cycads, online edition. Available from: www.cycadlist.org (accessed 25 July 2025).
  6. Calonje, M.A., Taylor Blake, A.S., Stevenson, D.W., Holzman, G. & Ramos, Y.A. (2012) Zamia lindleyi: A misunderstood species from the highlands of western Panama. Proceedings of CYCAD 2008, the 8th International Conference on Cycad Biology, Panama City, Panama, January 2008. Memoirs of the New York Botanical Garden 106: 419–437.
  7. Chamberlain, C.J. (1912) Morphology of Ceratozamia. Botanical Gazette 53 (1): 1–20. https://doi.org/10.1086/330707
  8. Chamberlain, C.J. (1919) The Living Cycads. University of Chicago Press, Chicago, IL, USA, 172 pp.
  9. Chang, J.-T., Chao, C.-T., Nakamura, K., Liu, H.-L., Luo, M.-X. & Liao, P.-C. (2022) Divergence with gene flow and contrasting population size blur the species boundary in Cycas Sect. Asiorientales, as inferred from morphology and RAD-Seq data. Plant Sciences 13: 824158. https://doi.org/10.3389/fpls.2022.824158
  10. Chemnick, J. & Gregory, T.J. (1995) A new species of Ceratozamia (Zamiaceae) from Oaxaca, Mexico with comments on distribution, habitat, and relationships. Phytologia 79 (1): 51–57.
  11. Chemnick, J., Gregory, T.J. & Salas-Morales, S. (1997a) A revision of Dioon tomasellii (Zamiaceae) from western Mexico, a range extension of D. merolae, and clarification of D. purpusii. Phytologia 83: 1–6.
  12. Chemnick, J., Gregory, T.J. & Salas-Morales, S. (1997b) Ceratozamia mixeorum (Zamiaceae), a new species from Oaxaca, Mexico with comments on distribution, habitat, and species relationships. Phytologia 83 (1): 47–52.
  13. de Candolle, A. (1868) Microcycas calocoma. Prodr. [A.P. de Candolle] 16 (2): 538.
  14. de Laubenfels, D.J. & Adema, F. (1998) A taxonomic revision of the genera Cycas and Epicycas gen. nov. (Cycadaceae). Blumea 43: 351–400.
  15. De Luca, P., Sabato, S. & Vázquez Torres, M. (1984) Dioon tomasellii (Zamiaceae), a new species with two varieties from western Mexico. Brittonia 36: 223–227.
  16. Donaldson, J. (2004) Saving ghosts? The implications of taxonomic uncertainty and shifting infrageneric concepts in the Cycadales for Red Listing and conservation planning. In: Walters, T. & Osborne, R. (Eds.) Cycad Classification: Concepts and Recommendations. CABI Publishing, Wallingford, UK, pp. 13–22.
  17. Dyer, R.A. (1956) A new cycad from the Cape Province. J. S. African Bot. 22: 1–4.
  18. Dyer, R.A. (1965) New species and notes on type specimens of South African Encephalartos. J. S. African Bot. 31: 111–121.
  19. Dyer, R.A. & Verdoorn, I.C. (1969) Encephalartos manikensis and its near allies. Kirkia 7 (1): 147–158.
  20. Faden, R.B. & Beentje, H.J. (1989) Encephalartos kisambo, a new cycad from Kenya, with a note on E. tegulaneus. Utafiti 2 (1): 7–10.
  21. González, D. & Vovides, A.P. (2002) Low intralineage divergence in Ceratozamia (Zamiaceae) detected with nuclear ribosomal DNA ITS and chloroplast DNA trnL-F non-coding region. Syst. Bot. 27 (4): 654–661.
  22. Griffith, M.P., Magellan, T.M. & Tomlinson, P.B. (2014) Variation in leaflet structure in Cycas (Cycadales: Cycadaceae): Does anatomy follow phylogeny and geography? International J. Plant Sci. 175 (2): 241–255. https://doi.org/10.1086/673884
  23. Grobbelaar, N. (2002) Cycads, with Special Reference to the Southern African Species. Published by the author, 331 pp.
  24. Gutiérrez-Ortega, J.S., Pérez-Farrera, M.A., Vovides, A.P., Chávez-Cortázar, A., López, S., Santos-Hernández, N.G. & Rúiz-Roblero, S.K. (2021) Ceratozamia sanchezae (Zamiaceae): A new cycad species from Chiapas Highlands (Mexico). Phytotaxa 500 (3): 201–216. https://doi.org/10.11646/phytotaxa.500.3.4
  25. Gutiérrez-Ortega, J.S., Pérez-Farrera, M.A., Mitsuhiko, A.M., Sato, P., Suyama, Y., Calonje, M., Vovides, A.P., Kajita, T. & Watano, Y. (2023) The phylogenetic reconstruction of the Neotropical cycad genus Ceratozamia (Zamiaceae) reveals disparate patterns of niche evolution. Molecular Phylogenetics and Evolution 190 (2024): 107960. https://doi.org/10.1016/j.ympev.2023.107960
  26. Harris, J.G. & Harris, M.W. (2000) Plant Identification Terminology, An Illustrated Glossary, 2nd Ed. Spring Lake Publishing, Spring Lake, UT, 216 pp.
  27. Hassemer, G., Prado, J. & Baldini, R.M. (2020) Diagnoses and descriptions in plant taxonomy: Are we making proper use of them? Taxon 69 (1): 1–4. https://doi.org/10.1002/tax.12200
  28. Haynes, J.L., Whitelock, L.M., Schutzman, B. & Adams, R.S. (2008) A new endemic Ceratozamia from Honduras (Cycadales: Zamiaceae). Cycad Newsletter 31 (2/3): 16–21.
  29. Haynes, J.L. (2009a) Expanded Glossary of Cycad Terms. The Cycad Society, 51 pp. Available from: www.cycad.org/documents/expanded_glossary.pdf (accessed 22 October 2023).
  30. Haynes, J.L. (2009b) Illustrated Glossary of Cycad Terms. The Cycad Society. Available from: www.cycad.org/publications/illustrated_glossary.htm (accessed 22 October 2023).
  31. Haynes, J.L. (2022) Critical evaluation of two formal descriptions of the same species of Ceratozamia (Zamiaceae) from northern Oaxaca, Mexico, and the formal synonymization of C. martinezii under C. aurantiaca. Phytotaxa 575 (3): 265–275. https://doi.org/10.11646/phytotaxa.575.3.4
  32. Haynes, J.L. (2023) Critical review of “Monograph of Ceratozamia (Zamiaceae, Cycadales): an endangered genus” published in PhytoKeys 208: 1–102 (2022). Phytotaxa 612 (2): 159–200. https://doi.org/10.11646/phytotaxa.612.2.4
  33. Haynes, J.L. & Bonta, M.A. (2007) An emended description of Dioon mejiae Standl. & L.O. Williams (Zamiaceae). Proceedings of CYCAD 2005, the 7th International Conference on Cycad Biology, Xalapa, Mexico, January 2005. Memoirs of the New York Botanical Garden 97: 418–443.
  34. Hill, K.D. (2004) Character evolution, species recognition and classification concepts in the Cycadaceae. In: Walters, T. & Osborne, R. (Eds.) Cycad Classification: Concepts and Recommendations. CABI Publishing, Wallingford, UK, pp. 23–44.
  35. Hill, K.D., Nguyên, H.T. & Loc, P.K. (2004) The genus Cycas (Cycadaceae) in Vietnam. Bot. Rev. 70 (2): 134–193.
  36. Hill, K.D. & Yang, S.-L. (1999) The genus Cycas (Cycadaceae) in Thailand. Brittonia 51 (1): 48–73.
  37. Hill, W. (1865) Catakidozamia, Hill. Gard. Chron. 22 (47): 1107.
  38. Hurter, P.J.H. (1995) Two newly described cycads from Africa. Phytologia 78 (6): 409–416.
  39. IPNI (2023) International Plant Names Index. Published on the Internet: http://www.ipni.org, The Royal Botanic Gardens, Kew, Harvard University Herbaria & Libraries and Australian National Herbarium. (accessed 25 October 2023).
  40. IUCN (2023) IUCN/Species Survival Commission Cycad Specialist Group, Coral Gables, FL, USA. Available from: www.cycadgroup.org (accessed 16 October 2023).
  41. Jacquin, N. (1791) Observationes botanicae. Collectanea [Jacquin] 3: 167–276.
  42. Lindstrm, A.J. (2004) Morphological characters useful in determining species boundaries in Cycas (Cycadaceae). In: Walters, T. & Osborne, R. (Eds.) Cycad Classification: Concepts and Recommendations. CABI Publishing, Wallingford, UK, pp. 45–55.
  43. Lindström, A.J. & Hill, K.D. (2007) The genus Cycas (Cycadaceae) in India. Telopea 11 (4): 463–488.
  44. Lindström, A.J., Hill, K.D. & Stanberg, L.C. (2008) The genus Cycas (Cycadaceae) in the Philippines. Telopea 12 (1): 119–145.
  45. Lindström, A.J., Hill, K.D. & Stanberg, L.C. (2009) The genus Cycas (Cycadaceae) in Indonesia. Telopea 12 (3): 385–418.
  46. Lundell, C.L. (1939) Studies of Mexican and Central American Plants VII. Lloydia 2 (2): 73–108.
  47. Malaisse, F., Sclavo, J.-P. & Crosiers, C. (1993) Recherches sur les Encephalartos Lehm. (Zamiaceae) d’Afrique centrale 2. Apport de la morphologie foliaire dans la differenciation specifique. Bull. Jard. Bot. Natl. Belg. 62: 205–219.
  48. Martínez-Domínguez, L., Nicolalde-Morejón, F., Lorea-Hernández, F.G., Vergara-Silva, F. & Stevenson, D.W. (2020) A novelty in Ceratozamia (Zamiaceae, Cycadales) from the Sierra Madre del Sur, Mexico: Biogeographic and morphological patterns, DNA barcoding and phenology. PhytoKeys 156: 1–25. https://doi.org/10.3897/phytokeys.156.53502
  49. Martínez-Domínguez, L., Nicolalde-Morejón, F. & Stevenson, D.W. (2017a) Qualitative and quantitative morphological evidence for recognition of a new species within Ceratozamia (Zamiaceae) from Mexico. Phytotaxa 317: 17–28. https://doi.org/10.11646/phytotaxa.317.1.2
  50. Martínez-Domínguez, L., Nicolalde-Morejón, F., Vergara-Silva, F. & Stevenson, D.W. (2016) Integrative taxonomy of Mexican cycads: Biogeography, morphology and DNA barcoding corroborate a new sympatric species in Ceratozamia (Zamiaceae). Phytotaxa 268 (1): 25–45. https://dx.doi.org/10.11646/phytotaxa.268.1.2
  51. Martínez-Domínguez, L., Nicolalde-Morejón, F., Stevenson, D.W. & Vergara-Silva, F. (2017b) A new species of Ceratozamia (Zamiaceae) from the Sierra Norte of Puebla, Mexico. Brittonia 69 (4): 516–523. https://doi.org/10.1007/s12228-017-9486-0
  52. Martínez-Domínguez, L., Nicolalde-Morejón, F., Vergara-Silva, F. & Stevenson, D.W. (2021) A new Mexican Ceratozamia (Zamiaceae) species with notes on reproductive phenology. Nordic J. Bot. 39 (11): 1–11. https://doi.org/10.1111/njb.03348
  53. Martínez-Domínguez, L., Nicolalde-Morejón, F., Vergara-Silva, F. & Stevenson, D.W. (2022) Monograph of Ceratozamia (Zamiaceae, Cycadales): An endangered genus. PhytoKeys 208: 1–102. https://doi.org/10.3897/phytokeys.208.80382
  54. McDonald, J.H. (2014) Basic concepts of hypothesis testing. In: Handbook of Biological Statistics (3rd ed.). Sparky House Publishing, Baltimore, Maryland. Available from: www.biostathandbook.com/hypothesistesting.html (accessed 13 October 2023).
  55. Melville, R. (1957) Encephalartos in central Africa. Kew Bull. 12 (2): 237–257.
  56. Miquel, F.A.W. (1847) Over eenige nieuwe of zeldame Cycadeën in den Hortus Botanicus Amsterdam. Derde gedeelte. Tijdschrift voor de wisen natuurkundige wetenschappen, uitgegeven door de eerste klasse van het Kon. Ned. Instituut van Wetenschappen, Letteren en Schoone Kunsten 1: 197–208.
  57. Miquel, F.A.W. (1852) Sur une espèce nouvelle de Zamia des Indies Occidentales, introduite dans l’éstablissement L. Van Houtte, à Gand. Fl. Serres Jard. Eur. 7 (6): 141–142.
  58. Miquel, F.A.W. (1870) A la connaissance des cycadees. Adansonia 9: 154–180.
  59. Moretti, A., De Luca, P., Sclavo, J.P. & Stevenson, D.W. (1989) Encephalartos voiensis (Zamiaceae), a new east central African species in the E. hildebrandtii complex. Annals of the Missouri Botanical Garden 76 (3): 934–938.
  60. Nicolalde-Morejón, F., Vergara-Silva, F., González-Astorga, J., Vovides, A.P. & Espinosa de los Monteros, A. (2009) Reciprocal illumination of morphological characters upon a molecular hypothesis supports the proposal of a new species of cycad from Mexico. Systematics and Biodiversity 7 (1): 73–79. https://doi.org/10.1017/S1477200008002879
  61. Nix Sensor Ltd. (2023) Nix Mini 3, Nix Sensor Ltd. Available from: https://www.nixsensor.com/mini-3-color-sensor/ (accessed 5 October 2023).
  62. Norstog, K. (1980) Chromosome numbers in Zamia. Caryologia 33: 419–428.
  63. Osborne, R. & Hendricks, J. (1985) A world list of cycads. Encephalartos 3: 13–17.
  64. Osborne, R. & Walters, T. (2004) In search of the true tree: Guidelines for classification. In: Walters, T. & Osborne, R. (Eds.) Cycad Classification: Concepts and Recommendations. CABI Publishing, Wallingford, UK, pp. 195–217.
  65. Pérez-Farrera, M.A., Gutiérrez-Ortega, J.S., Gregory, T.J., Chemnick, J., Salas-Morales, S., Calonje, M. & Díaz-Jiménez, P. (2022) Ceratozamia schiblii (Zamiaceae): A new cycad species from the eastern mountains of Oaxaca, Mexico. Taxonomy 2022 (2): 324–338. https://doi.org/10.3390/taxonomy2030025
  66. Pérez-Farrera, M.A., Gutiérrez-Ortega, J.S., Vovides, A.P., Calonje, M. & Díaz-Jiménez, P. (2021a) Ceratozamia dominguezii (Zamiaceae): A new cycad species from southeastern Mexico. Taxonomy 1 (4): 345–359. https://doi.org/10.3390/taxonomy1040026
  67. Pérez-Farrera, M.A., Gutiérrez-Ortega, J.S., Haynes, J.L., Chemnick, J., Salas-Morales, S.H., Calonje, M. & Vovides, A.P. (2021b) Ceratozamia aurantiaca (Zamiaceae): A new cycad species from the northern rainforests of Oaxaca, Mexico. Taxonomy 1 (3): 243–255. https://doi.org/10.3390/taxonomy1030018
  68. Pérez-Farrera, M.A., Vovides, A.P., González, D., López, S., Hernandez-Sandoval, L. & Martínez, M. (2017) Estimation of genetic variation in closely related cycad species in Ceratozamia (Zamiaceae: Cycadales) using RAPDs markers. Int. J. Trop. Biol. 65 (1): 305–319.
  69. Pérez-Farrera, M.A., Vovides, A.P., Martinez-Camilo, R., Martinez Melendez, N. & Iglesias, C. (2009) A reassessment of the Ceratozamia miqueliana species complex (Zamiaceae) of southeastern Mexico, with comments on species relationships. Systematics and Biodiversity 7 (4): 433–443. https://doi.org/10.1017/S1477200009990211
  70. Pérez-Farrera, M.A., Vovides, A.P., Ruiz-Castillejos, C., Galicias, S., Cibrián-Jaramillo, A. & Lopez, S. (2016) Anatomy and morphology suggest a hybrid origin of Zamia katzeriana (Zamiaceae). Phytotaxa 270 (3): 161–181. https://dx.doi.org/10.11646/phytotaxa.270.3.1
  71. Pócs, T. & Luke, Q. (2007) A new species of Encephalartos (Zamiaceae) from Tanzania. Journal of East African Natural History 96 (2): 193–201.
  72. Regel, E.A. (1857) Zwei neue Cycadee. Bull. Soc. Imp. Naturalistes. Moscou. 30 (1): 161–191.
  73. Robbertse, P.J., Vorster, P. & van der Westhuizen, S. (1988a) Encephalartos verrucosus (Zamiaceae): A new species from the north-eastern Transvaal. South African Journal of Botany 54 (4): 487–490.
  74. Robbertse, P.J., Vorster, P. & van der Westhuizen, S. (1988b) Encephalartos graniticolus (Zamiaceae): A new species from the north-eastern Transvaal. South African Journal of Botany 54 (4): 363–366.
  75. Sass, C., Little, D.P., Stevenson, D.W. & Specht, C.D. (2007) DNA barcoding in the Cycadales: Testing the potential of proposed barcoding markers for species identification of cycads. PLoS ONE 2 (11): e1154. https://doi.org/10.1372/journal.pone.0001154
  76. Sattler, R. (2022) Kaplan’s Principles of Plant Morphology: A critical review. Botanical Review 88: 257–270. https://doi.org/10.1007/s12229-022-09280-8
  77. Schutzman, B. (1984) A new species of Zamia L. (Zamiaceae, Cycadales) from Chiapas, Mexico. Phytologia 55 (5): 299–304.
  78. Schutzman, B. (2004) Systematics of the Meso-American Zamia (Zamiaceae). In: Walters, T. & Osborne, R. (Eds.) Cycad Classification: Concepts and Recommendations. CABI Publishing, Wallingford, UK, pp. 159–172.
  79. Schutzman, B., Adams, R.S., Haynes, J.L. & Whitelock, L.M. (2008) A new endemic Zamia from Honduras (Cycadales: Zamiaceae). Cycad Newsletter 31 (2/3): 22–26.
  80. Segalla, R., Soares Pimenta, R. & Calonje, C. (2023) Zamia multidentata (Cycadales, Zamiaceae), a new arborescent species of Zamia from Acre, Brazil. Phytotaxa 598 (1): 21–31. https://doi.org/10.11646/phytotaxa.598.1.2
  81. Singh, R. & Radha, S. (2008) A new species of Cycas (Cycadaceae) from Karnataka, India. Botanical Journal of the Linnean Society 158: 430–435.
  82. Sperotto, P., Acevedo-Rodríguez, P., Vasconcelos, T.N.C. & Roque, N. (2020) Towards a standardization of terminology of the climbing habit in plants. Botanical Review 86: 180–210. https://doi.org/10.1007/s12229-020-09218-y
  83. Standley, P.C. & Williams, L.O. (1951) Dioon mejiae, a new cycad from Honduras. Ceiba 1: 36–38.
  84. Stevenson, D.W. (1990) Morphology and systematics of the Cycadales. Memoirs of the New York Botanical Garden 57: 8–55.
  85. Stevenson, D.W. (1993) The Zamiaceae in Panama with comments on phytogeography and species relationships. Brittonia 45 (1): 1–16.
  86. Stevenson, D.W. & Sabato, S. (1986) Typification of names in Ceratozamia Brongn., Dion Lindl., and Microcycas A. DC. (Zamiaceae). Taxon 35 (3): 578–584. https://doi.org/10.2307/1221921
  87. Stevenson, D.W., Sabato, S. & Vázquez Torres, M. (1986) A new species of Ceratozamia (Zamiaceae) from Veracruz, Mexico with comments on species relationships, habitats, and vegetative morphology in Ceratozamia. Brittonia 38 (1): 17–26.
  88. Taylor, A.S., Haynes, J.L. & Holzman, G. (2008) Taxonomical, nomenclatural, and biogeographical revelations in the Zamia skinneri species complex (Cycadales: Zamiaceae) of Central America. Botanical Journal of the Linnean Society 158: 399–429.
  89. The Plant List. (2013) The Plant List, version 1.1. Published on the Internet: www.theplantlist.org/tpl1.1/search?q= Cycas+circinalis (accessed 27 October 2023).
  90. Turland, N.J., Wiersema, J.H., Barrie, F.R., Gandhi, K.N., Gravendyck, J., Greuter, W., Hawksworth, D.L., Herendeen, P.S., Klopper, R.R., Knapp, S., Kusber, W.-H., Li, D.-Z., May, T.W., Monro, A.M., Prado, J., Price, M.J., Smith, G.F. & Zamora, J.C. (eds.) (2025) International Code of Nomenclature for algae, fungi, and plants (Shenzhen Code) adopted by the Nineteenth International Botanical Congress Shenzhen, Madrid, July 2024. University of Chicago Press, Chicago, IL. Available from: www.iaptglobal.org/_functions/code/madrid (accessed 10 July 2025). https://doi.org/10.7208/chicago/9780226839479.001.0001
  91. Turner, I., J.-P. Sclavo & F. Malaisse (2006) Un nouvel Encephalartos Lehm. (Zamiaceae) de Zambie. Biotechnol. Agron. Soc. Environ. 10 (3): 181–183.
  92. Vázquez Torres, M., Moretti, A. & Carvajal-Hernandez, C. (2009) A new species of Ceratozamia (Zamiaceae) from Veracruz, Mexico. Delpinoa 50–51: 129–133.
  93. Vorster, P. (1990) Encephalartos aemulans (Zamiaceae), a new species from northern Natal. South African Journal of Botany 56: 239–243.
  94. Vorster, P. (1995) The identity of Encephalartos lebomboensis. In: Vorster, P. (ed.) Proceedings of the Third International Conference on Cycad Biology. Cycad Society of South Africa, Stellenbosch, South Africa, pp. 245–254.
  95. Vorster, P. (1996a) Encephalartos msinganus (Zamiaceae): A new species from Kwa-Zulu-Natal. South African Journal of Botany 62 (2): 67–70.
  96. Vorster, P. (1996b) Encephalartos venetus (Zamiaceae): A new species from the Northern Province. South African Journal of Botany 62 (2): 71–75.
  97. Vorster, P. (1996c) Encephalartos senticosus (Zamiaceae): A new species from the northern Kwa-Zulo Natal and Swaziland. South African Journal of Botany 62 (2): 76–79.
  98. Vorster, P. & Gereau, R.E. (1998) Encephalartos ituriensis (Zamiaceae): An emended description. Adansonia 20 (1): 211–216.
  99. Vorster, P. & Heibloem, P. (1995a) Encephalartos imbricans (Zamiaceae): A new species from Uganda. Novon 5 (4): 388–394.
  100. Vorster, P. & Heibloem, P. (1995b) Encephalartos successibus (Zamiaceae): A new species from Uganda. South African Journal of Botany 61 (6): 347–351.
  101. Vovides, A.P. (1983) Systematic studies on the Mexican Zamiaceae. I. Chromosome numbers and karyotypes. American Journal of Botany 70: 1002–1006.
  102. Vovides, A.P., Avendaño, S., Pérez-Farrera, M.A. & González-Astorga, J. (2008a) A new species of Ceratozamia (Cycadales, Zamiaceae) from Veracruz, Mexico. Novon 18 (1): 109–114.
  103. Vovides, A.P., Avendaño, S., Pérez-Farrera, M.A. & Stevenson, D.W. (2012) What is Ceratozamia brevifrons (Zamiaceae)? Brittonia 64 (1): 35–42.
  104. Vovides, A.P., Pérez-Farrera, M.A., González, D. & Avendaño, S. (2004a) Relationships and phytogeography in Ceratozamia (Zamiaceae). In: Walters, T. & Osborne, R. (Eds.) Cycad Classification: Concepts and Recommendations. CABI Publishing, Wallingford, UK, pp. 109–125.
  105. Vovides, A.P., Pérez-Farrera, M.A., González-Astorga, J. & Iglesias, C. (2008b) A new species of Ceratozamia (Zamiaceae) from Oaxaca, Mexico with comments on habitat and relationships. Botanical Journal of Linnean Society 157: 169–175.
  106. Vovides, A.P., Pérez-Farrera, M.A., Salinas-Rodríguez, M.M., Galicia, S., Díaz-Jiménez, P., Calonje, M. & Gutiérrez-Ortega, J.S. (2022) Morphological and anatomical analyses clarify the species definition of Ceratozamia latifolia Miq. (Zamiaceae) and lead to the description of a new species: Ceratozamia reesii. Phytotaxa 575 (3): 224–252. https://doi.org/10.11646/phytotaxa.575.3.2
  107. Vovides, A.P., Pérez-Farrera, M.A., Schutzman, B., Iglesias, C., Hernández-Sandoval, L.H. & Martínez, M. (2004b) A new species of Ceratozamia (Zamiaceae) from Tabasco and Chiapas, Mexico. Bot. J. Linn. Soc. 146 (1): 123–128.
  108. Vovides, A.P. & J.D. Rees (1983) Ceratozamia microstrobila (Zamiaceae), a new species from San Luis Potosí, Mexico. Madroño 30 (1): 39–42.
  109. Vovides, A.P., Vázquez Torres, M., Schutzman, B. & Iglesias, C. (1993) A new species of Ceratozamia (Zamiaceae) from Querétaro and Hidalgo, Mexico. Novon 3 (4): 502–506.
  110. Walters, T. & Osborne, R. (2004) Cycad Classification: Concepts and Recommendations. CABI Publishing, Oxfordshire, UK, 267 pp.
  111. Walters, T., Osborne, R. & Decker, D. (2004) ‘We hold these truths…’. In: Walters, T. & Osborne, R. (Eds.) Cycad Classification: Concepts and Recommendations. CABI Publishing, Wallingford, UK, pp. 1–22.
  112. Warszewicz, J. (1851) Bericht uber zwei neue Zamien, nebft ubbilbung berfelben. Allg. Gartenzeit 19: 145–146.
  113. WCVP (2022) World Checklist of Vascular Plants, version 2.0. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet: http://wcvp.science.kew.org/taxon/328822-2 (accessed 27 October 2023).
  114. WFO (2022) Cycas circinalis L. Published on the Internet: www.worldfloraonline.org/taxon/wfo-0000631521 (accessed 27 October 2023).

How to Cite

Haynes, J.L. (2026) Critical review of morphological trait assessment in cycad (Cycadophyta: Cycadales) taxonomy: Importance of consistency and need for standardization. Phytotaxa 738 (1): 1–335. https://doi.org/10.11646/phytotaxa.738.1.1