Ceratozamia leptoceras: Identification, Habitat and Status

Ceratozamia leptoceras is a cycad of the Sierra Madre del Sur in the state of Guerrero, south-western Mexico, where it grows on limestone rocks in cloud forest between 1,170 and 1,400 m (about 3,840 to 4,590 ft). Described in 2020, it is the only species of the genus Ceratozamia known from Guerrero and the north-westernmost member of the genus on the Pacific side of Mexico. Its name, “thin-horned”, refers to the short, slender horns on the scales of its male cones. Only three populations are known, the 2022 monograph of the genus considers it Endangered, and it has not yet been assessed by the IUCN; it is practically absent from collections.

Key facts about Ceratozamia leptoceras

Accepted name: Ceratozamia leptoceras Mart.-Domínguez, Nic.-Mor., D.W.Stev. & Lorea-Hern. (2020), accepted by The World List of Cycads (version 2026.08.15) and by the World Checklist of Vascular Plants (WCVP, the database behind POWO, read via GBIF)
Former names and synonyms: none
Family: Zamiaceae, order Cycadales
Common names: no English name; “shalukaá” among the Mixtec people of Guerrero
Natural range: Mexico, Guerrero, Sierra Madre del Sur (municipalities of Tlacoachistlahuaca and Cochoapa El Grande), 1,170 to 1,400 m
IUCN status: Not Evaluated; Endangered (EN) proposed in the 2022 monograph of the genus, a preliminary assessment with no official standing
CITES and other protection: CITES Appendix I (whole genus, since 1985); Annex A in the European Union, seeds included
Documented hardiness: no data (see Cold hardiness)
Light and soil: in the wild, karst rocks in cloud forest, under a warm temperate climate with summer rain; no published growing advice
Habit and adult size: above-ground trunk 30 to 150 cm long and 11 to 35 cm across; a crown of 7 to 37 (rarely up to 55) drooping leaves, 0.9 to 2.8 m long
In the UK, US and Australia: no garden declares it to BGCI PlantSearch (see In cultivation)
Toxicity: no data for the species; treat it as poisonous, like all cycads (see Toxicity and precautions)

How to recognise Ceratozamia leptoceras

Ceratozamia leptoceras is a fairly large Ceratozamia with an above-ground trunk and a crown of many drooping leaves, which carry narrow, thin, flat leaflets on a petiole bristling with slender prickles. The original description (2020) and the 2022 monograph of the genus describe it as follows:

Trunk: above ground, 30 to 150 cm long and 11 to 35 cm in diameter, upright, then leaning or lying; persistent, triangular, reddish-brown cataphylls, densely woolly when they emerge.
Leaves: 7 to 37, sometimes up to 55 according to the monograph (7 to 50 in the original description), drooping, 93.5 to 281 cm long; green with a sparse reddish-brown down when they emerge, then hairless. They appear in flushes of 9 to 15 that mature almost together. The petiole, 45 to 85 cm long and coppery green, carries 50 to 75 thin prickles 4.8 to 6.8 mm long; the axis is also prickly.
Leaflets: 22 to 61 pairs, linear, membrane-thin, flat, green and hairless, with a pointed, symmetrical tip; the middle ones measure 28 to 43.5 cm by 1.9 to 2.8 cm, and their points of attachment are usually coppery green.
Male cones: usually single, rarely in pairs, cylindrical and upright, 40 to 45 cm long and 6 to 7.8 cm across, brownish yellow when they emerge, then yellowish green with brownish hairs, on a woolly stalk 13 to 19 cm long. Each scale ends in a long, narrow sterile part with two straight, thin horns only 1 to 2.3 mm long, the feature that gave the species its name.
Female cones: single, cylindrical, upright, 23.5 to 28 cm long and 9.5 to 11 cm across, coppery green with greyish-black hairs when ripe, on a stalk 11 to 16 cm long; 56 to 81 scales in 8 or 9 rows of 7 to 9, with straight, sturdy horns 6.3 to 8.1 mm long and an abundant down at their base.
Seeds: egg-shaped, 2.4 to 2.7 cm long and 1.4 to 1.8 cm across, with a pinkish-white fleshy coat before ripening, light brown when ripe.

Hybrids

No hybrid, natural or garden-made, has been documented.

Possible confusion

No other Ceratozamia grows in Guerrero, so confusion is unlikely in the wild. The original description compares it mainly with the two species it most resembles, Ceratozamia robusta (Chiapas and Guatemala) and Ceratozamia subroseophylla (Veracruz):

Ceratozamia leptoceras: drooping leaves, green when they emerge, with a coppery-green petiole and axis; thin prickles; linear, membrane-thin leaflets 1.9 to 2.8 cm wide; female cone with 7 to 9 scales per row; grows on limestone rocks in cloud forest;
Ceratozamia robusta: upright leaves, dark brown when they emerge; sturdy prickles; lance-shaped, papery leaflets 3.1 to 3.9 cm wide; larger female cone (26 to 40 cm); evergreen tropical forest and oak forest on clay soils;
Ceratozamia subroseophylla: upright leaves, yellowish brown when they emerge; sturdy prickles; lance-shaped, papery leaflets 2.4 to 4 cm wide; smaller female cone (15.5 to 23.5 cm); evergreen tropical forest only.

The 2022 monograph distinguishes it from Ceratozamia oliversacksii, of western Oaxaca, by its membrane-thin rather than papery leaflets, with the main differences in the cones: a long, linear sterile tip on the male cone scales and an abundant down at the base of the female cone scales. In the key of the original description, it also stands apart from the other drooping-leaved species with thin leaflets, such as Ceratozamia whitelockiana, Ceratozamia mixeorum or Ceratozamia delucana, which have lance-shaped leaflets.

Taxonomy

Ceratozamia leptoceras is accepted by The World List of Cycads and by the WCVP, the database behind POWO (read via GBIF on 30 October 2026), which records its publication in PhytoKeys 156 in 2020. It has no synonyms. It was described by Lilí Martínez-Domínguez, Fernando Nicolalde-Morejón, Francisco Lorea-Hernández, Francisco Vergara-Silva and Dennis Stevenson in an article entitled “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).

The authors followed an integrative approach that combines geography, detailed cone morphology, DNA barcoding and the timing of cone development. Two DNA regions (ITS and matK) identified only 19 of the 31 species of Ceratozamia tested, a success rate of 61%; the Guerrero plants nevertheless showed two diagnostic positions of their own in matK, shared by all five individuals sequenced. Their female cones are also on a different schedule from those of Ceratozamia robusta and Ceratozamia subroseophylla: they are receptive in March and April, against May to July in the two related species, which the authors suggest may act as a reproductive barrier.

Etymology and history

The epithet comes from the Greek leptos, “thin” or “fine”, and keras, “horn”, and describes the short, thin horns of the male cone scales (original description; The World List of Cycads, after Haynes 2022).

The species was found in two stages. While reviewing the Ceratozamia specimens of the herbarium of the Faculty of Sciences of the National Autonomous University of Mexico (FCME), the authors came across a sterile specimen collected in February 1984 by Francisco Lorea-Hernández in the municipality of Cochoapa El Grande. The genus had never been reported from Guerrero, and this locality was the northernmost known for Ceratozamia on the Pacific side of Mexico; without cones, however, the specimen could not be identified with certainty. Fieldwork in 2019 relocated the plants. The holotype, a female plant, was collected on 26 June 2019 in the municipality of Tlacoachistlahuaca, at 1,400 m, by L. Martínez-Domínguez and F. Nicolalde-Morejón (number 1867); it is kept at the CIB herbarium of the Universidad Veracruzana, with isotypes at MEXU and NY.

Common names

No English name is recorded. The Mixtec people of the region call the plant “shalukaá” (original description, 2020; 2022 monograph). No other name is documented.

In the wild

Ceratozamia leptoceras is known only from Guerrero, in the Sierra Madre del Sur. According to the original description, it grows on karst rocks in cloud forest, and in the transition between cloud forest and oak forest, between 1,170 and 1,400 m, under a semi-warm, subhumid temperate climate with summer rain and 2,000 to 2,500 mm (79 to 98 in) of rain a year. Its two closest relatives grow instead on clay soils with scattered volcanic rocks. The cloud forests of this area are still little affected by human activity, but this type of forest is one of the most threatened in Mexico (2022 monograph).

The original description also gives its calendar: male cones mature from January to May, female cones in June and July and seeds in August and September. No pollinator study has been published.

Conservation status and regulation

Ceratozamia leptoceras has not yet been assessed for the IUCN Red List (The World List of Cycads, version 2026.08.15; the Red List data distributed through GBIF contain no entry for it on 30 October 2026). In the 2022 monograph, the authors propose classifying it as Endangered (EN): only three populations are known, one of them with only about thirty adult plants. This preliminary assessment has no official standing.

Like the whole genus, it has been covered by CITES Appendix I since 1 August 1985, and by Annex A of Regulation (EC) No 338/97 in the European Union (annexes now set by Regulation (EU) 2026/1383, applicable since 29 June 2026), seeds included. Species+ does not yet list the species by name, since it was described after the CITES reference list, but the listing covers the whole genus (Ceratozamia spp.) and therefore applies to it (Species+, checked on 30 October 2026).

This general information does not replace the official texts: check the regulations in force before buying or exchanging plants, ask the seller for proof of origin, and prefer plants raised from cultivated seed.

Growing Ceratozamia leptoceras

No growing advice specific to Ceratozamia leptoceras has been published, and no cultivation report is documented: described in 2020 and known from three populations, the species does not appear to be in cultivation outside Mexico.

Its habitat gives a few pointers: a mid-altitude cloud forest, very wet in summer, on limestone. Partial shade, a free-draining mix, generous watering in the warm season and much less in winter is the most consistent approach, but it has not been tested in any published trial.

Outdoor and in-ground cultivation

No outdoor planting of the species has been documented anywhere. Its large size, with leaves that can approach 3 m, would need room in a sheltered, partly shaded spot.

Container cultivation

No container trial has been published. Young plants of other trunk-forming Ceratozamia are commonly grown in pots, but nothing specific is known for this species.

In cultivation in the UK, US and Australia

No garden declares Ceratozamia leptoceras to BGCI PlantSearch, and the online catalogue of Montgomery Botanical Center (Coral Gables, Florida), which holds one of the largest cycad collections, lists no accession (both queried on 30 October 2026). No living plant is therefore known in British, American or Australian public collections.

Propagation

No data exist for the species. Like all Ceratozamia, it has separate male and female plants; in the wild, male cones shed pollen from January to May while female cones are receptive in March and April, so in cultivation pollen would have to be stored or cone timing matched. Propagation would be from fresh seed, cleaned wearing gloves.

Pests and diseases

No pest or disease specific to the species has been documented. In cultivation, cycads mainly suffer from rot in cold, waterlogged soil and from scale insects.

Cold hardiness

No cold-hardiness data exist for Ceratozamia leptoceras. It lives in cloud forest between 1,170 and 1,400 m under a warm temperate climate, and no observation says whether it can take frost.

Mediterranean and European experience

No cultivation result has been published in Europe, either in the ground or in a pot, and the Jardin zoologique tropical in La Londe-les-Maures (Var, on the French Riviera) has published no observation of this species. Until trials exist, keep it frost-free.

United Kingdom, United States and Australia

No cold record and no commercial hardiness rating have been published. In the UK it would be a plant for a heated glasshouse.

Toxicity and precautions

No toxicity study specific to Ceratozamia leptoceras has been published. The risk is well documented in other cycads: their tissues, and above all their seeds, contain toxic glycosides (cycasin, macrozamin), from which methylazoxymethanol is derived, a compound harmful to the liver and nervous system. Dogs, livestock and people can be seriously poisoned. In the absence of evidence to the contrary, treat the plant as poisonous: keep seeds and leaves out of reach of children and animals, wear gloves to clean seeds, and if any part is swallowed, call a poison centre, a doctor or a vet straight away.

Traditional uses

The 2022 monograph records no use. Only its Mixtec name, “shalukaá”, attests to its place in local culture.

Frequently asked questions

What does the name Ceratozamia leptoceras mean?

“Thin-horned”. The epithet, from Greek, describes the short, slender horns at the tip of the male cone scales.

Where does it grow?

Only in the Sierra Madre del Sur of Guerrero, Mexico, on limestone rocks in cloud forest between 1,170 and 1,400 m. It is the only Ceratozamia known from that state.

How long has it been known?

A specimen was collected in 1984 but stayed unidentified in a herbarium. The species was only relocated in the field and described in 2019–2020.

Is it endangered?

Probably. The IUCN has not assessed it yet, but the 2022 monograph considers it Endangered: only three populations are known, one with about thirty adult plants.

Is it cold-hardy?

Nobody knows. No cold data exist, so it is safest to keep it frost-free.

Can I buy one?

Not without paperwork. It is covered by the listing of the whole genus in CITES Appendix I and in Annex A of the EU regulation, seeds included, and it does not appear to be offered in the trade.

Is it toxic?

Assume so. No analysis exists for the species, but the cycads studied contain serious toxins, especially in their seeds.

Sources

Reference sites

The World List of Cycads (version 2026.08.15), Ceratozamia leptoceras: https://cycadlist.org/scientific_name/889 — authors, publication, type, range, IUCN status (Not Evaluated), etymology. Checklist of the IUCN Cycad Specialist Group, reliable; reread on 30 October 2026.
World Checklist of Vascular Plants (WCVP, Royal Botanic Gardens, Kew), via GBIF, Ceratozamia leptoceras: https://api.gbif.org/v1/species/207874427 — accepted name, place of publication. Kew data, the basis of POWO, distributed by GBIF; consulted on 30 October 2026.
PubMed Central, A novelty in Ceratozamia (Zamiaceae, Cycadales) from the Sierra Madre del Sur, Mexico (2020): https://pmc.ncbi.nlm.nih.gov/articles/PMC7471474/ — original description: discovery, type, description, habitat, climate, phenology, Mixtec name, DNA barcoding, comparison with Ceratozamia robusta and Ceratozamia subroseophylla, keys. Peer-reviewed article, open access; reread on 30 October 2026.
PubMed Central, monograph of Ceratozamia (PhytoKeys 208): https://pmc.ncbi.nlm.nih.gov/articles/PMC9849018/ — description, range, preliminary conservation status, comparison with Ceratozamia oliversacksii. Peer-reviewed article, open access.
Species+ (UNEP-WCMC), Ceratozamia: https://speciesplus.net/species#/taxon_concepts/13147/legal — CITES Appendix I for the whole genus since 1 August 1985, Annex A in the European Union. Official CITES and EU database; checked on 30 October 2026.
BGCI PlantSearch: https://plantsearch.bgci.org/ — no garden declaring the species. Global database of garden lists; queried on 30 October 2026.
Montgomery Botanical Center, living collection: https://www.montgomerybotanical.org/research/living-collection/ — no accession of the species in its BG-BASE catalogue. Specialist cycad garden; catalogue queried on 30 October 2026.

Bibliography

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 [Original description; open access.]
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 [Description, range, preliminary status; open access.]
Haynes, J.L. (2022). Etymological compendium of cycad names. Phytotaxa 550(1): 1–31. https://doi.org/10.11646/phytotaxa.550.1.1 [Source of the etymology given by The World List of Cycads.]
Calonje, M., Stevenson, D.W. & Osborne, R. (2026). The World List of Cycads, version 2026.08.15. Montgomery Botanical Center, Coral Gables. https://doi.org/10.5281/zenodo.21958524 [Reference checklist.]