Norw. J. Bot. 27: 275 (1980).
Protolog: Data lacking.
Protolog type data: Data lacking.
Type locality: Spain, Canary Islands, Gomera, W of Arure, on rock, 750 m, 14. April 1978, H. Krog & H. Østhagen 2971 (O - holotype; BM, UPS - isotypes).
Type locality coordinates: Data lacking.
Molecular barcode: Data lacking.
Thallus: fruticose, fragile, shrubby to subpendulous, up to 8 cm long, with a number of moderately to richly branched laciniae from a common holdfast. Laciniae stramineous, shiny, subterete, angular or flattened, 0.2 - 1.0 - 1.5 mm broad, with numerous, short, divergent branchlets terminating in nodules or hook-shaped structures, thinner branches often nodulose, with fragmentation areas. Pseudocyphellae linear, longitudinally arranged, in flattened branches mainly marginal. Soralia absent. Cortex ca. 30 µm thick, peripherical chondroid tissue forming continuous upper and lower layers in younger parts, becoming disrupted in older parts, medulla dense, sometimes with a few imbedded chondroid strands. Pycinia not seen. Apothecia rare, lateral, up to 5 mm in diameter, disc flat to convex, thalline exciple often with short laciniae, spores 10 - 12 / 3µm (Krog & Østhagen 1980: 275).
Photobiont: Data lacking.
Chemistry: Salacinic acid (Krog & Østhagen 1980: 275).
Ecology: Saxicolous.
Distribution Type: Endemic in the Canary Islands: Gomera, Hierro (Serusiaux 2010: 535). Hierro, Gomera, Tenerife, Fuerteventura, Lanzarote (Hernandez-Padron & Perez-Vargaz (2010: 87). "The specimens reported as R. hamulosa from Fuerteventura (van den Boom & Etayo 2006) all belong to R. crispatula (Sérusiaux et al. 2010: 535).
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