Cochemiea thomasii

Name and rocky site in Sinaloa

POWO accepts Cochemiea thomasii García-Mor., Rodr.González, J.García-Jim. & Iamonico. The name was published in 2020. The later combination Mammillaria thomasii from 2021 is now a synonym. Plants discovered by Thomas Linzen in 2012 were examined in the field in autumn 2018 and spring 2019. [García Morales et al. 2020, protologue pp. 1–2, POWO record, as of 11 October 2026] [2-WWW]

The described site lies in the municipality of Cosalá in Sinaloa at 300–325 m above sea level. Plants occupy vertical rock faces in tropical deciduous forest. They usually grow 5–10 m above the base of the face. The publication documented one population in which about 150 individuals were counted. The authors presented a preliminary assessment of high threat based on the small known range and population size. This was an assessment proposed in the protologue. [García Morales et al. 2020, pp. 4–5]

Stems hanging from rock

Cylindrical stems initially grow upright, then hang down. They branch at the base and along the sides, reaching about 60 cm long or more and 3.5–5 cm in diameter. The older base becomes corky. Roots were described as fibrous and spreading. Conical tubercles bear round areoles 2–3 mm in diameter at their tips. Young areoles are woolly, while older ones become bare. [García Morales et al. 2020, p. 2–4; ryc. 1]

Central spines are straight, numbering 1–4, and 7–13 mm long. There are 10–15 radial spines. In comparison with C. halei, the combined difference in central spine number, length and habit is important. C. halei has more, longer central spines and prostrate stems, while C. thomasii develops hanging stems on vertical faces. [García Morales et al. 2020, p. 2, 4–5; tabela 1, klucz]

Flower, splitting fruit and seed

Scarlet flowers have a tubular perianth with bilateral symmetry. They measure 30–42 mm long and 12–15 mm wide at the top. Anthers and the style project beyond the perianth. At the described site, flowering occurred in February and March, and fruit ripening in July and August. This is the phenology of the habitat in Sinaloa. [García Morales et al. 2020, pp. 2–4]

Fruits are ovoid, 7–9 mm long and 6–8 mm wide. Initially green, they become reddish brown and open through a lateral slit. The black pear-shaped seeds are about 1.3 mm long and 0.8 mm wide. The seed surface was examined with scanning microscopy. The protologue documents similarity to C. halei and a set of traits distinguishing the new species. It did not include DNA sequencing. [García Morales et al. 2020, p. 2–5; ryc. 1D, tabela 1]

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