Gelidium nayaritense Rodríguez D., Quiroz-González N. & Ponce-Márquez M. sp. nov. (Figs 3–4).

Type: — MEXICO. Nayarit: Sayulita, intertidal, 20°52’29’’N; 105°26’72 W, 17 June 2017, D. Rodríguez & N. Quiroz-González, holotype FCME 10875 (Fig. 3a) in FCME (Faculty of Science, Mexico), isotypes: FCME 10869, 10876, 10880, 10881, 10884 in FCME (Faculty of Science, Mexico).

Description: —Plants a turf of purple-red thalli, with cylindrical prostrate stolon attached to substratum with brushlike haptera and erect linear to clavate axes, with irregular to smooth margins, cylindrical at base and flattened above, mostly without ramification. When branches occasionally present, irregularly arranged with one order of ramification, 0.4–1.0 cm high, 0.2–1 mm width, 0.1–0.3 mm thick (Fig. 3a–d). Axes in transverse section ovoid, elliptical, elliptical acute or elliptic in half moon, decreasing in diameter towards apex. Shape of vegetative apices acute (Fig. 3e–f). Cortex of 2–3 layers of rounded cells, 6–9 µm in diameter (Fig. 3g –h), outer cortical cells irregularly arranged in surface view. Medulla of 3–6 rows of circular or subcircular cells in transverse section, 12–15 μm in diameter, and with very large intercellular spaces. Internal rhizoidal filaments in small groups within the medulla and concentrated in the subcortex (Fig. 3g –h). Tetrasporangial sori located in proximal parts of ordinary branches, ovoid, 180–390 µm wide and 285 µm long, with small sterile margins. Tetrasporangia irregularly arranged in sori, ovoid, spherical, 20–28 µm in diameter, 21–25 µm long, cruciately divided. Gametophytes not observed.

Etymology: —The species epithet referred to the state Nayarit, Mexico, where the type specimen was collected.

Distribution and Habitat:—Sayulita in Nayarit to Zihuatanejo in Guerrero. Intertidal rocks, with low incidence of light and high waves.

Barcode sequences of holotype specimen: —rbc L GenBank accession number MT 798865 and COI-5P GenBank accession number MT 799807 .

Other examined material:— MEXICO. Guerrero: Troncones, intertidal, 17°46’4’’N; 101°43’31’’W, 15 January 2017, D. Rodríguez & N. Quiroz-González, 10888, 10889 (FCME).