Origin and Habitat: Eriosyce tenebricaSN|2370]]SN|2815]] is common from west of Domeyko to the valley of the Rio Choros in the Chilean regions of Atacama and Coquimbo (West of the territory of the Eriosyce napinaSN|2815]]SN|2370]] var. fankhauseri)
Habitat and ecology: It occurs in rocky soil with good drainage in coastal vegetation together with Oxalis giganteaSN|32524]]SN|32524]] and Eulychnia brevifloraSN|7528]]SN|7528]], mainly in large ravines and valleys that reach the coast of the Region of Atacama, between 300 to 750 meters. It grow flat with the ground and is often covered by dark brownish sand and dust.

• Eriosyce napina var. tenebrica (F.Ritter) Romulski
• Eriosyce napina subs. tenebrica (F.Ritter) Ferryman
• Eriosyce tenebrica (F.Ritter) Katt.
• Thelocephala tenebrica F.Ritter

• Eriosyce napina (Phil.) Katt.
• Chilenia napina (Phil.) Backeb.
• Chileorebutia napina (Phil.) F.Ritter
• Echinocactus napinus Phil.
• Hildmannia napina (Phil.) Kreuz. & Buining
• Malacocarpus napinus Britton & Rose
• Neochilenia napina (Phil.) Backeb. ex Dölz
• Neochilenia napina (Phil.) Y.Itô
• Neoporteria napina (Phil.) Backeb.
• Notocactus napinus (Phil.) A.Berger
• Thelocephala napina (Phil.) Y.Itô
• Thelocephala roseiflora Y.Itô
• Eriosyce napina subs. challensis I.Schaub & Keim
• Thelocephala challensis (I.Schaub & Keim) Faúndez & Saldivia
• Eriosyce napina var. imitans (Backeb.) nov. comb. ined.
• Neochilenia imitans Backeb.
• Neoporteria reichei f. imitans (Backeb.) Donald
• Eriosyce napina var. mitis (Phil.) Donald & G.D.Rowley
• Echinocactus mitis Phil.
• Hildmannia mitis (Phil.) Kreuz. & Buining
• Neochilenia mitis (Phil.) Backeb.
• Neochilenia napina var. mitis (Phil.) Backeb. ex Dölz
• Neoporteria napina var. mitis (Phil.) Donald & G.D.Rowley
• Eriosyce napina var. neoreichei (Backeb.) nov. comb. ined.
• Neochilenia neoreichei Backeb.
• Neoporteria reichei f. neoreichei (Backeb.) Donald & G.D.Rowley
• Reicheocactus neoreichei (Backeb.) Backeb.
• Eriosyce napina var. spinosior (Backeb.) nov. comb. ined.
• Neochilenia napina var. spinosior Backeb.
• Neoporteria napina var. spinosior Backeb.
• Neoporteria napina f. spinosior (Backeb.) Donald & G.D.Rowley

• Eriosyce napina var. duripulpa (F.Ritter) Katt.
• Chileorebutia duripulpa F.Ritter
• Eriosyce duripulpa F.Ritter
• Eriosyce napina subs. duripulpa (F.Ritter) Katt.
• Neochilenia duripulpa (F.Ritter) Backeb.
• Neoporteria napina var. duripulpa (F.Ritter) A.E.Hoffm.
• Neoporteria reichei f. duripulpa (F.Ritter) Donald & G.D.Rowley
• Thelocephala duripulpa (F.Ritter) F.Ritter

• Eriosyce napina var. fankhauseri (F.Ritter) Romulski
• Eriosyce napina subs. fankhauseri (F.Ritter) Mächler & Helmut Walter
• Neoporteria napina var. fankhauseri (F.Ritter) A.E.Hoffm.
• Thelocephala fankhauseri F.Ritter

• Eriosyce napina var. lembckei Katt.
• Eriosyce napina subs. lembckei Katt.
• Neochilenia lembckei Backeb.
• Neoporteria napina var. lembckei (Backeb.) A.E.Hoffm.
• Neoporteria reichei var. lembckei (Backeb.) Donald & G.D.Rowley
• Neoporteria reichei f. lembckei (Backeb.) Donald & G.D.Rowley
• Thelocephala lembckei (Backeb.) F.Ritter

• Eriosyce napina var. riparia (Mächler & Helmut Walter) Romulski
• Eriosyce napina subs. riparia Mächler & Helmut Walter
• Thelocephala riparia (Mächler & Helmut Walter) Faúndez & Saldivia

• Eriosyce napina var. tenebrica (F.Ritter) Romulski
• Eriosyce napina subs. tenebrica (F.Ritter) Ferryman
• Eriosyce tenebrica (F.Ritter) Katt.
• Thelocephala tenebrica F.Ritter

Description: Eriosyce napinaSN|2370]]SN|2370]] var. tenebrica is a slow growing, small geophytic cactus usually unbranched 2813]SN|2813]] was made by Friedrich Ritter in 1980. Fred Kattermann introduced her to the genus Eriosyce in 1994.

Bibliography: Major references and further lectures
1) Friedrich Ritter “Kakteen in Südamerika: Ergebnisse meiner 20 jährigen Feldforschung.” Volume 3, Chile, 1980.
2) David Hunt, “Succulent Plant Research.” Volume 1, p. 119, Richmond 1994.
3) Edward F. Anderson “Das große Kakteen-Lexikon.” Eugen Ulmer KG, Stuttgart 2005
4) Wikipedia, "Eriosyce tenebrica - Wikipedia, Die freie Enzyklopädie" 2014 url = "url{https://de.wikipedia.org/w/index.php?title=Eriosyce_tenebrica&oldid=126639566},[Online; Stand 4. November 2016]
5) LUEBERT F. & P. PLISCOFF “Sinopsis bioclimática y vegetacional de Chile”. Editorial Universitaria, Santiago. 2006.

Cultivation and Propagation: This species has the fame to be difficult to grow, but it is really not so difficult. Whatever view one adopts, it is worth a place in every cactus collection. The only problem is that it is very slow growing and for its long root, necessitates a rather larger, or deeper at least, pot that one might expect for the size of plant. Like all thick-rooted species, it requires careful watering (rot sensitive), and patience to match its slow growth. During the winter rest, the plant may pull near the surface of the potting mix. Sometimes they are grafted to avoid root rot problems. Suited for sunny-bright exposure; they can tolerate light shade. They prefer airy exposures. They like warmth (recommended minimum winter temperature 5° C). But plant kept perfectly dry can easily survive in winter night temperatures below 0° C
Pests & diseases: It is especially prone to rot, therefore, underpot in a smaller container filled with a very porous compost.
Propagation: Direct sow after last frost (it usually doesn't produces offsets) or graft. Seeds can be sown in the spring or summer. The seedlings should not be disturbed until they are well rooted, after which they can be planted separately in small pots.