[1] Cochemiea thomasii forms large, slender clusters of hanging stems that are 60 cm (24 in) or longer.

[citation needed] It has 1–4 stiff, white with reddish-brown tipped central spines, 0.7–1.3 cm (0.28–0.51 in) long, which turn gray with age, and 10–15 radial spines that are initially white, turning brown to black, and are also 0.7–1.3 cm (0.28–0.51 in) long.

[citation needed] The red flowers bloom from young tubercles, measuring 3–4.2 cm (1.2–1.7 in) long, with a vertical, crooked-hemmed, and long flower tube.

[2] Plants are found growing near Cosalá, Sinaloa, in deciduous tropical forest growing on vertical rock cliffs from the coast towards the Sierra Madre Occidental at elevations between 300 and 325 m (984 and 1,066 ft).

[2] This species was described in 2020 by Leccinum J. García Morales, Rodrigo González González, Jesús García Jiménez, and Duilio Iamonico, and named after Thomas Linzen, a German scholar of the genus Mammillaria.