Papery spines and a small stem
Sclerocactus papyracanthus (formerly also Toumeya papyracantha) retains its current placement in Sclerocactus in POWO. The Mexican plants described in 2023 had a solitary stem, obconical to cylindrical, 2.5–5.5 cm long and 1.5–2 cm wide, and fleshy roots. The stem surface bore tubercles ending in small areoles. [Ortiz-Brunel et al. 2023] [2-WWW]
Its most distinctive feature is the long central spine, usually one, sometimes accompanied by additional spines. In the material studied, it measured 21–42 mm and was flattened, flexible and often curved upwards. Its surface shows a central thickening, and its margins have fine hairs. Its colour ranges from whitish or light brown to grey. The radial spines, usually 6–8 in number, are much shorter. [Ortiz-Brunel et al. 2023]
Among grasses, this spination resembles the dead leaves of surrounding plants. The similarity in shape, texture and colour helps explain why the small cactus is difficult to find outside the flowering period. The authors describe this resemblance as a feature of its appearance in the habitat. Its effect on the frequency with which plants are eaten remains a separate question to investigate. [Ortiz-Brunel et al. 2023]
Flowers, fruits and seeds
The flowers of the Mexican specimens were 2–2.5 cm in diameter and 2–3.2 cm long. Their whitish tepals had brownish central stripes, the stamen filaments were white and the style greenish. The stigma divided into five lobes. Comparing these features with spine and seed structure confirmed the identification of the plants at the new site. [Ortiz-Brunel et al. 2023]
The ripening fruit changed colour from green to greenish purple. It was 6–10 mm long and 4–6 mm wide, with a few scales in its upper part. The seeds were black, flattened and obovate, around 2.5–3 mm long. The presence of fruits and numerous small plants documented reproduction in the local population. [Ortiz-Brunel et al. 2023]
From a photograph to a confirmed range
The species was previously known from Arizona, New Mexico and western Texas. A photograph posted on Naturalista in 2020 drew researchers' attention to Chihuahua. Two expeditions, in March and April 2023, located the plants, described the habitat and collected documentation material. Specimens were deposited in the IBUG and MEXU herbaria, allowing the identification to be referred to preserved botanical material. [Ortiz-Brunel et al. 2023]
The searches found 38 plants. Under the adopted size classes, 23 were classified as seedlings less than 1 cm tall, two as juveniles 1–3 cm tall, and 13 as adults exceeding 3 cm. This is the number of specimens found during the expeditions. Classification by size characterises the structure of the discovered group, while determining the age of individual plants would require longer tracking of their development. [Ortiz-Brunel et al. 2023]
Grasses, salinity and the flowering rhythm
The site lies in the municipality of Ascensión at an elevation of around 1200 m. The plants grew on saline ground in a community dominated by the grasses Bouteloua gracilis and B. hirsuta. They were found beside tussocks or within rings formed by grasses. Other cacti also occurred nearby, including Coryphantha macromeris and Echinocereus fendleri. Earlier descriptions of US sites often indicated higher elevations, around 1500–2200 m. [Ortiz-Brunel et al. 2023]
Buds were observed in March, and buds, flowers and fruits together in April. These two visits document spring reproductive activity in the newly described population. Two small individuals, 1.2–1.5 cm tall, also flowered. The authors interpret their appearance as neoteny, reaching reproductive maturity while retaining features of a juvenile form. The directly documented fact is flowering at such a small stem size. [Ortiz-Brunel et al. 2023]
The new site extends the confirmed range of the species into Mexico and adds to its habitat description. Combining a photograph, relocation of the plants and herbarium specimens allowed an observation requiring verification to become a documented floristic record. The detailed description of local plants also retains information about their variation relative to populations previously known from the USA. [Ortiz-Brunel et al. 2023]
Related articles
Materials from the author's archive
The species also appears in Konrad Szychowski's private material archive. [Bydgoski Klub Miłośników Kaktusów 2002, file p. 7] [Kaktusy i Inne 2005a, file p. 11]
Synonyms and names in the literature
Toumeya papyracantha · Papyrocactus papyracanthus · Echinocactus papyracanthus · Mammillaria papyracantha [2-WWW]