Further studies on the species diversity of the marine planktonic diatom genus Skeletonema (Bacillariophyta) in the Mexican Pacific Author Hernández-Becerril, David U. text Phytotaxa 2023 2023-08-09 607 3 182 196 http://dx.doi.org/10.11646/phytotaxa.607.3.2 journal article 10.11646/phytotaxa.607.3.2 1179-3163 8243269 Skeletonema grevillei Sarno et Zingone Figs 12–17 References: Zingone et al . 2005 , p. 144, figs 5 A–F, 6 A–I; Sarno et al . 2007 , p. 162, figs 2 A–J; Naik et al . 2010 , p. 291, figs 3–6; Gu et al . 2012 , p. 254, figs 15–17; Bužančić et al . 2017 , p. 195, figs 2–5. Description: Chains are relatively thin, delicate, mostly long (2–9 cells per chain, usually more than 6) and straight to slightly curved ( Fig. 12 ). Usually there are two chloroplasts per cell ( Fig. 12 ). Valves are flat to slightly convex, with a relatively high valve mantle ( Figs 13–16 ). Most specimens show siliceous ridges, sometimes poorly developed, dividing valve face and mantle ( Figs 13, 15 , small arrows). Additional ridges are also found at the bases of the fultoportulae ( Figs 14, 16 , small arrows). The valves have very irregular areolae with rectangular, polyedric or elongate areolae ( Figs 16, 17 ). Details of the cingular bands were not observed. The fultoportulae are open throughout them ( Figs 13–16 ), and the TF’s have their tips irregularly truncated ( Figs 13, 15, 16 ). Each IF fuses to one of the sibling valve ( Figs 13, 14 ). Three to four satellite pores surround each fultoportula ( Fig. 17 , arrows). The TR’s are marginal ( Figs 13, 16 , arrows), and have a long tube, with an inflated tip ( Figs 13, 15, 16 , arrows), whereas the IR is almost marginal, but very short ( Fig. 14 , arrow). Measurements: cell diameter 3.4–5.8 μm, areolae density 33–51 in 10 μm ( Table 1 ).