Neidium vandusenense Hamilton, Savoie, Sayre, Skibbe, Zimmermann & Bull, 2019, sp. nov.

Neidium vandusenense sp. nov. Figs 19–44 Individuals examined for morphological analyses: n = 61, examined for molecular analysis: n = 7. Valves linear to linear elliptic with apiculate extended apices (Figs 19–30). Valve length 96–116 μm, width 20.0– 23.0 μm. Striae oblique to mildly convergent at apices, 14–17 in 10 μm. Areolae round to elliptical, 14–16 in 10 μm. Voigt faults on secondary side of valve. Central area transapically expanded, covering 1/3 to 1/2 the valve width. Linear ghost striation markings present along edge of central area (Figs 21–22, 25, 27–28). Axial area linear-elliptical from mid-valve to apex. In LM, raphe filiform and linear-elliptical. Three or more longitudinal canals present along each margin. Central raphe ends deflected hooks, terminal ends forming bifurcate lacinia. Small terminal hyaline area present at apex (Fig. 20, arrow). In SEM external view, valves more or less linear with rounded margins (Figs 31, 33). Apices broadly protracted and mantle at apex recessed not forming linear sides (Figs 31, 33). Raphe linear with a broken thickened ridge along primary side and weak to no ridge along secondary side (Figs 32, 34). Proximal raphe ends form distinct small hooks in opposite directions on small central mound (Fig. 32). Distal raphe ends form broad triangular lacinia with curved expansion at mantle base (Figs 33, 35). Axial area with randomly positioned surface depressions (Figs 32, 34). Areolae depressions on external valve face with recessed finger-forming silicate cribra (Figs 34, 36). Three to four flat, longitudinal canals present along each margin (Figs 32, 36). Internal valve: Central area elevated with ghost striae (Fig. 37). Central helictoglossae offset with small silica interconnection. Terminal helictoglossae form vertically on terminal nodule (Figs 38, 39). Canals flat with valve face, all of equal size and form (Figs 40, 41); towards apex canals extends to hyaline terminal nodule at apex (Fig. 38). Areolae chambered with transapical interconnections (Fig. 41 arrow, on mantle). Areolae covered by hymenes (Figs 42, 43). Renilimbia (2–6) around areolae along axial area, and longitudinal canals (Fig. 42). Renilimbia also randomly scattered around areolae on the valve face. Copulae open bands, with 2 rows of pores (Figs 43, 44). Type:— CANADA. British Columbia: Vancouver, VanDusen Botanical Garden, J. Holmes, December 28, 2016. Small stream at the end of Livingstone Lake (pond) (holotype: CANA! 126257-7, fig. 22 holotype specimen, circled on slide). Isotype ANSP GC65327 (circled specimen on slide). Genbank #s See table 2. Etymology:—The specific epithet (vandusenense), is recognized for the collection site at the VanDusen Botanical Garden. Registration: http//phycobank.org/102030 Observations:—Plastid rbc L DNA sequence, size (96–116 μm), valve outline, 3–4 longitudinal canals, ghost striae along the margins of the central area and recessed mantle margins at the apices identify this taxon. Neidium vandusenense can be compared to N. siveri Metzeltin & Lange-Bertalot (2007: 179) with a similar valve outline, but N. vandusenense is distinguished by the larger size (64–74 μm long, N. siveri), more than one longitudinal canal and the weak oblique striation formation. Neidium vandusenense can also be compared to N. grande Gandhi (1959: 313, as N. grandis) with respect to general valve outline, protracted apices, and multiple longitudinal canals. N. vandusenense is differentiated from N. grande by larger size (45–55 μm, N. grande), linear to slightly triundulate valve margins (not elliptic), and stria density (26–28 in 10 μm, N. grande). No ghost striae were observed in N. grande. Another comparison can be made with N. capitellatum Gandhi (1959: 313, as N. capitellata) with respect to valve outline, although N. capitellatum is smaller (46–86 μm long) and the apices are capitate. In North America compare with N. affine var. humerus Reimer (Patrick & Reimer 1966: 392) with respect to similar valve outline and ghost striae along the central area. N. vandusenense is larger than N. affine var. humerus (41–78 μm long), the valve margins of N. vandusenense are more linear and sometimes weakly triundulate, the apices more protracted and 3 + longitudinal canals versus 1(2) in N. affine var. humerus. The stria and areolae densities of N. affine var. humerus are also higher.

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