taxonID	type	description	language	source
03D687D4936EFFA7FF494FBCFA39307A.taxon	materials_examined	Holotype: LAF 6956 A (Figs. 3 – 17), Sackett Bank, NWGMx (28 ° 38.0 ’ N; 89 ° 33.028 ’ W), 65 – 68 m deep, leg. J. L. Richards & S. Fredericq, 7. ix. 2014. Additional material examined: LAF 6970 B (Figs. 18 – 23), Dry Tortugas Vicinity, SEGMx (24 ° 31.494 ’ N; 83 ° 19.793 ’ W), 69 m deep, leg. J. L. Richards & S. Fredericq, 10. ix. 2014 (collected from site in field), 15. xii. 2014 (collected from microcosm).	en	Richards, Joseph L., Fredericq, Suzanne (2018): Sporolithon sinusmexicanum sp. nov. (Sporolithales, Rhodophyta): a new rhodolith-forming species from deepwater rhodolith beds in the Gulf of Mexico. Phytotaxa 350 (2): 135-146, DOI: 10.11646/phytotaxa.350.2.2, URL: http://dx.doi.org/10.11646/phytotaxa.350.2.2
03D687D4936EFFA7FF494FBCFA39307A.taxon	etymology	Etymology: The specific epithet refers to the Gulf of Mexico, the locality of the holotype and Florida specimen.	en	Richards, Joseph L., Fredericq, Suzanne (2018): Sporolithon sinusmexicanum sp. nov. (Sporolithales, Rhodophyta): a new rhodolith-forming species from deepwater rhodolith beds in the Gulf of Mexico. Phytotaxa 350 (2): 135-146, DOI: 10.11646/phytotaxa.350.2.2, URL: http://dx.doi.org/10.11646/phytotaxa.350.2.2
03D687D4936EFFA7FF494FBCFA39307A.taxon	description	Description DNA sequences: DNA sequences from the holotype: rbc L (GB accession = KY 994126), psb A (GB accession = MF 034549), LSU (GB accession = KY 980437), and UPA (GB accession = KY 980429); and from the Florida specimen: LSU (GB accession = KY 980438), rbc L (GB accession = KY 994127), and psb A (GB accession = MF 034550). Morphology and Habit: Thallus non-geniculate, forming biogenic rhodoliths that are smooth to warty (Fig. 3) or with numerous protuberances (Fig. 18). Found growing in benthic rhodolith beds at a depth of 65 – 69 m. Vegetative Anatomy: It was not determined with certainty if thallus construction is dimerous or monomerous, though some areas of the thallus appeared putatively monomerous. New vegetative layers (Fig. 4) formed by a secondary hypothallium with one to two layers of basal filaments (Fig. 5). Hypothallial cells rectangular in shape, 11.5 – 20 μm long x 3 – 7 μm wide. Perithallium with abundant cell fusions (Figs. 6, 20); secondary pit connections not observed. Perithallial cells 6.6 – 19 μm long x 7 – 10.6 μm wide. Meristematic cells 4.2 – 12 μm long x 7.8 – 15.3 μm wide (Figs. 7, 8, 20, 21). Epithallium (Figs. 7, 8, 20, 21) a single layer of armored epithallial cells that are 2 – 3 μm long x 4 – 7.8 μm wide, with thick, heavily calcified cell walls and a trapezoidal-shaped lumen. Reproduction: Tetrasporangial sori are sloughed off after spore release. Sori were observed in the process of sloughing off the surface of the rhodoliths (Figs. 9 – 13, 22). Pores with rosette cells that remained intact (n = 5) showed 10 – 12 rosette cells surrounding each tetrasporangial compartment pore (Fig. 14). Sections showed tetrasporangial compartments at the protuberance tip (Figs. 15 – 17) and no buried tetrasporangial structures embedded in the perithallium (Figs. 15, 19). Intact tetrasporangial compartment measured 83 μm long x 59 μm wide (n = 1), subtended by a stalk cell 14 μm long x 28 μm wide (n = 1) (Fig. 16). Tetrasporangial compartments surrounded by paraphyses with non-elongated cells at the base of tetrasporangial compartments (Figs. 16, 17). Female and male structures were not observed.	en	Richards, Joseph L., Fredericq, Suzanne (2018): Sporolithon sinusmexicanum sp. nov. (Sporolithales, Rhodophyta): a new rhodolith-forming species from deepwater rhodolith beds in the Gulf of Mexico. Phytotaxa 350 (2): 135-146, DOI: 10.11646/phytotaxa.350.2.2, URL: http://dx.doi.org/10.11646/phytotaxa.350.2.2
03D687D4936EFFA7FF494FBCFA39307A.taxon	distribution	Distribution: Sackett Bank, NWGMx, and the vicinity of the Dry Tortugas, SEGMx.	en	Richards, Joseph L., Fredericq, Suzanne (2018): Sporolithon sinusmexicanum sp. nov. (Sporolithales, Rhodophyta): a new rhodolith-forming species from deepwater rhodolith beds in the Gulf of Mexico. Phytotaxa 350 (2): 135-146, DOI: 10.11646/phytotaxa.350.2.2, URL: http://dx.doi.org/10.11646/phytotaxa.350.2.2
03D687D4936EFFA7FF494FBCFA39307A.taxon	discussion	Comments: Unidentified spherical inclusions were observed in the perithallium of specimen LAF 6970 B, which may be unidentified life history stages of microalgal organisms (Fig. 23), as reported in Krayesky-Self et al. (2017).	en	Richards, Joseph L., Fredericq, Suzanne (2018): Sporolithon sinusmexicanum sp. nov. (Sporolithales, Rhodophyta): a new rhodolith-forming species from deepwater rhodolith beds in the Gulf of Mexico. Phytotaxa 350 (2): 135-146, DOI: 10.11646/phytotaxa.350.2.2, URL: http://dx.doi.org/10.11646/phytotaxa.350.2.2
