Kadenicarpus horripilus

Name and distribution

Kadenicarpus horripilus is the accepted species name. POWO gives a natural range from Querétaro to Veracruz in Mexico. Its basionym is Mammillaria horripila, described in 1838. Names found in the literature include Turbinicarpus horripilus, Gymnocactus horripilus and Bravocactus horripilus. The current combination was published in 2019. [2-WWW]

The 2019 systematic publication discusses populations associated with Metztitlán canyon in Hidalgo. The spine-microstructure study included seeds TCG 40201 originating from San Pablo in the same state. These places describe the material studied. The current accepted range in POWO is broader. [Vázquez-Sánchez et al. 2019, Vázquez-Sánchez et al., p. 415. Mosco, p. 121, Table 1] [Mosco 2009, Vázquez-Sánchez et al., p. 415. Mosco, p. 121, Table 1] [2-WWW]

Hard spines with projections

In Mosco's study, the central spine had a woody texture and a sharp tip. The epidermis was continuous and formed feathery projections. Beneath it lay layers of thin-walled cells, with compact, thick-walled fibres deeper inside. The hard core and external projections are separate parts of spine structure. [Mosco 2009, p. 121–124, tab. 2, ryc. 1D]

Epidermal relief with feathery projections also occurred in Turbinicarpus laui and some other taxa studied. Similarity of spine surfaces therefore crosses current genus boundaries. A broader set of seed, stem-tissue and DNA features indicates the separation of Kadenicarpus and Turbinicarpus. [Mosco 2009, Mosco, pp. 121–127. Vázquez-Sánchez et al., p. 412] [Vázquez-Sánchez et al. 2019, Mosco, pp. 121–127. Vázquez-Sánchez et al., p. 412]

Fibres in cortical bundles

Small vascular bundles passing through cortical parenchyma contained xylem fibres. In the comparison of 35 taxa, this was a feature of the Kadenicarpus lineage studied. No fibres were found in the main stem xylem. Vessels lay among wide-band tracheids, and rays consisted of non-lignified parenchyma cells. [De la Rosa-Tilapa et al. 2019, online version, pp. 2–4]

Prismatic crystals were observed in the hypodermis and pith. The hypodermis lies beneath the epidermis and the pith at the stem centre, so the two findings concern separate zones. In K. pseudomacrochele subsp. minimus, the pith contained druses. Crystal distribution adds to the description of differences within the genus. [De la Rosa-Tilapa et al. 2019, wersja online, p. 2–3]

Distinctness of the evolutionary lineage

K. horripilus and the tested taxa of the K. pseudomacrochele complex formed a strongly supported lineage in the 2019 analysis. Its recognition combined smooth seed microsculpture with fibres in cortical bundles and prismatic crystals in the hypodermis. The final feature is shared with Turbinicarpus. Recognition of the group arose from a combination of traits and molecular data. [Vázquez-Sánchez et al. 2019, p. 409, 412, 416–417]

Analysis of biomineral composition

The 2022 publication presents a biomineral from the hypodermis of K. horripilus in a comparison of X-ray analyses. The EDS spectrum provided elemental composition information, and the electron-microscopy image showed mineral form. This method supplements anatomical observation of the hypodermis. Precise distinction between calcium oxalate monohydrate and dihydrate requires analysis of mineral structure. [De la Rosa-Tilapa et al. 2022, p. 9, ryc. 7A]

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