Name, type and discovery
The accepted name is Thelocactus tepelmemensis T.J.Davis, H.M.Hern., G.D.Starr & Gómez-Hin. The species was discovered during an expedition in February 2017, and type material was collected in January 2018. Specimen Hernández and colleagues 4128 is preserved in MEXU. The holotype is number 1471315. The comparative description was based on 20 individuals and herbarium material. [2-WWW] [Davis et al. 2018, POWO; p. 115–116]
Habit and diagnostic traits
Stems are solitary or form clusters with lateral shoots. They have 11–13 vertical, tuberculate ribs. Typical areoles bear 8–9 spines, poorly differentiated into radial and central ones. Small extrafloral nectaries were found only near flowering areoles. The description gives flowers as 13–23 mm long and reddish purple. [Davis et al. 2018, p. 117–119, 121, tabela 1]
Seeds are broadly oval and keeled, 1.06–1.21 mm long and 0.78–1.00 mm wide. An expanded rim surrounds the hilum, the scar left by seed attachment. The micropyle lies within this rim. In the T. leucacanthus material compared, the micropyle lies outside the rim. This difference complements the stem and flower traits used in the diagnosis. [Davis et al. 2018, p. 118–121, ryc. 4, tabela 1]
Limestone faces and documented flowering
Sites known in the description were at 1420–1460 m in narrow limestone canyons. Plants grew on faces oriented mainly northeast and southeast, in crevices and on ledges of crumbling rock. The faces were shaded in the afternoon. Habitat observation indicates the combined importance of substrate, topography and exposure. [Davis et al. 2018, p. 119–121, ryc. 3]
Buds and flowers documented in January 2018 and February 2017 formed the basis for the December–February flowering period given by the authors. On two accessible trail sections beside the faces, 35 and 15 plants were counted over lengths of about 50 and 30 m. These were partial counts of visible plants in accessible parts of the canyon. [Davis et al. 2018, p. 119–121]