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Craspedostauros confusus Zidarova, M.de Haan, P.Ivanov, Hineva & Van de Vijver sp. nov. (Figs 9– 6, 8, 8–56) Description LM observations (Figs 9– 6, 8):— Frustules lanceolate in girdle view with convex, rarely weakly constricted (and hence biarcuate) margins, bearing numerous copulae. Longer valves linear with broadly rounded apices (Fig. 19), becoming narrowly lanceolate to elliptic-lanceolate in smaller valves with more cuneately rounded (Figs 21, 22), sometimes almost subrostrate apices (Fig. 23). Valve margins weakly convex (Fig. 21) to almost straight in the middle (Figs 20, 22, 24), lacking any constriction. Valve dimensions (n = 16): length 22.0–49.5 µm, width 4.5–6.5 µm. [Valves (n = 27) observed in other populations on Livingston Island during the study (Figs 60–77, 79) had a valve length of 18–50 µm and a valve width of 4.0–6.5 µm]. Axial area very narrow, linear (Figs 19–24, 28). Central area narrow, forming an almost rectangular (Fig. 19) to bow-tie-shaped fascia (Figs 20–24, 28), widening towards the valve margins. Raphe filiform, straight (Fig. 19) to weakly undulating, with expanded central raphe endings, and elongated terminal raphe fissures, unilaterally weakly bent (Figs 21, 24, 28). Striae rather coarse, parallel to occasionally very weakly radiate in the middle (Fig. 22), parallel to very weakly convergent near the apices (Figs 19, 24), 22–24 in 10 µm. Areolae, at least the larger ones bordering the axial area, weakly discernible in LM (Fig. 19). SEM observations (Figs 8–56):— Valve face weakly domed, with a deep mantle (Figs 48–51). External raphe branches straight with weakly undulating (Fig. 49) to straight (Fig. 51) central raphe endings, terminating in drop-like expanded pores (Figs 49, 51). Terminal raphe fissures continuing shortly onto the mantle, unilaterally hooked (Figs 48, 51). Axial area triangularly expanded at the apices, bearing a silica flap on one side, covering the terminal raphe fissures (Fig. 50). Striae uniseriate, composed of cribrate, rounded to elliptic areolae. Near the raphe areolae clearly larger (Figs 49, 50 and Figs 88–90). Cribrum structure of the areolae bordering the axial area possessing four to seven peripheral pores, and two to three central pores. All other areolae with cribra composed of 2–5 peripheral pores, lacking central pores (Figs 49, 50). Areolae continuing around the apices (Figs 48, 50), ca. 25–30 in 10 µm. Internal areolar openings rounded to elliptic (Figs 53–56). Internal raphe straight, located on a distinct sternum (Figs 52, 53). Central raphe endings terminating onto double helictoglossae (Figs 53, 55). Terminal raphe endings finish onto broad helictoglossae. Stauros narrow, located on a wider hyaline fascia (Figs 52, 53, 55). Type:— ANTARCTICA. South Shetland Islands: Livingston Island, Hannah Point, sample 14 (62° 39’13” S, 60° 36’ 41” W), marine epilithon, R. Zidarova, 16th December 2018 (holotype BR-4760! = Fig. 28, isotype Slide 417! (University of Antwerp, Belgium)). Etymology:— The species epithet, confusus, Latin for confusing, reflects the complex taxonomic history of the genus Craspedostauros in the Antarctic Region, and the possible long-term inclusion of this species within the more common Antarctic species C. laevissimus. Ecology and associated diatom flora:— Craspedostauros confusus sp. nov. was found as abundant in the epilithon of several tidal pools at Hannah Point (sample 14, type), Mongolian (Reserve) Port (samples DNA5 and MO’), and Caleta Argentina (sample LT6). The salinity level in the pools (when measured) ranged between 33 and 35 PSU (Table 1), and their diatom flora was dominated by various species, including Navicula spp., Melosira spp., Parlibellus sp., Tabulariopsis australis (Peragallo 1921: 67) D.M. Williams (1988: 249) and Tripterion margaritae (Frenguelli & Orlando 1958: 98) L.F. Fernandes & Sar (2009: 67)., Published as part of Zidarova, Ralitsa, Haan, Myriam De, Ivanov, Plamen, Hineva, Elitsa & Vijver, Bart Van De, 2022, The genus Craspedostauros E. J. Cox (Bacillariophyta) on the coasts of Livingston Island, Maritime Antarctica, pp. 1-24 in Phytotaxa 572 (1) on page 12, DOI: 10.11646/phytotaxa.572.1.1, http://zenodo.org/record/7305672, {"references":["Peragallo, M. (1921) Diatomees d'eau douce et diatomees d'eau salee. In: Deuxieme Expedition Antarctique Francaise (1908 - 1910) commandee par le Dr. Jean Charcot. Sciences Naturelles, Documents Scientifiques, Botanique, Masson et Cie, pp. 96 + Pl. https: // doi. org / 10.5962 / bhl. title. 64272","Williams, D. M. (1988) Tabulariopsis, a new genus of marine araphid diatom, with notes on the taxonomy of Tabularia Williams et Round. Nova Hedwigia 47: 247 - 254.","Frenguelli, J. & Orlando, H. A. (1958) Diatomeas y silicoflagelados del sector Antartico Sudamericano. Instituto Antartico Argentino Publicacion No. 5: 1 - 191.","Fernandes, L. F. & Sar, E. A. (2009) Fine morphology of Gomphonema margaritae Frenguelli & Orlando and its validation and transfer to Tripterion Holmes, Nagasawa & Takano. Diatom Research 24: 63 - 78. https: // doi. org / 10.1080 / 0269249 X. 2009.9705783"]}

Craspedostauros laevissimus (West & G.S.West 9: 8) Sabbe (00: 5) (Figs – 8, 7, 9– 7, 80–85) LM observations (Figs – 8, 7, 80–85):— Frustules rectangular, lanceolate in girdle view with weakly convex margins (Figs 7, 8), constricted in the middle (i.e. biarcuate), with numerous copulae (Fig. 18). Longest valves linear (Figs 80, 83, 85), linear-lanceolate, smaller valves becoming elliptic-lanceolate (Figs 4, 13, 15, 27). Apices broadly rounded (Figs 4, 15, 27), to almost cuneate (Figs 2, 3, 13). Valve margins in the middle ranging from occasionally almost straight (Fig. 83) to, usually, weakly (Figs 3, 5) to moderately (Figs 4, 9) convex. Valve dimensions (n = 26): valve length 20–42 µm, valve width 4.5–7.0 µm. Occasionally, weakly silicified valves, probably in state of formation, and easily “squashed” on the slides, appear to have a larger valve width (see for instance Figs 81, 82, 84). Axial area very narrow, linear. Central area variable in size, from very narrow (Figs 9, 11), almost rectangular (Figs 3, 16) to bow-tie-shaped fascia, widening towards the margin (Figs 2, 4, 5, 27). Raphe filiform, slightly curved to straight, with enlarged central raphe endings, and elongated, unilaterally bent, terminal raphe fissures. Striae fine, parallel, occasionally very weakly radiate in the middle, 28–30(32) in 10 µm. Areolae not or occasionally slightly individually discernible in LM. SEM observations (Figs 9– 7, 86–87):— Externally, valve face curving into a deep mantle (Figs 29, 38). Raphe almost straight (Figs 29, 32, 36, 39) or sometimes weakly undulating (Fig. 35). Central raphe endings weakly curved and enlarged (Figs 29–30, 32–33, 35, 37), occasionally straight and only weakly expanded (Figs 39–40). At the apices, axial area triangularly widening, forming a silica flap (Figs 38, 41) on one side covering the terminal raphe fissures. Fissures continuing shortly onto the mantle (Figs 31, 34, 35, 38, 39, 41), clearly unilaterally bent (Figs 35, 36) to weakly hooked (Fig. 38). Striae uniseriate, composed of cribrate areolae of almost equal size (Figs 30, 35, 39, 40, 45) to slightly larger near the axial area (Figs 37, 40, 41). Larger areolae, apparently formed by merging two adjacent areolae occasionally present near the axial area (Figs 31, 87, arrows). Areolae continuing around the apices (Figs 31, 34, 38). Cribra composed of usually four (Figs 34, 37, 40, 42), rarely five (Figs 33, 34, 40) peripheral pores, although very rarely, up to 6–7 very small peripheral pores were observed (Fig. 41), or very occasionally only 1–3 (Fig. 45). In general, areolae near the axial area more complex, with more peripheral pores, whereas areolae on the rest of the valve face simplified having a lower number of peripheral pores (Figs 40, 45). Central cribrum pores usually single or absent (Figs 30, 37, 40), occasionally 2–3 (Figs 31, 33, 34, 41). Areolae uniformly distributed over the valve face, ca. 40 in 10 µm. Internally, areolar openings square to rectangular (Figs 46, 47), to almost rounded (Figs 43, 45). Internal raphe branches straight, located on a distinctly raised sternum. Central raphe endings terminating onto double helictoglossae (Figs 43, 45, 46). Stauros narrow, located on a wider hyaline fascia (Figs 43–46). Terminal raphe endings finish onto broad helictoglossae (Figs 46, 47). Ecology and associated diatom flora:— The species was often found in the epilithon of tidal pools at Hannah Point (samples 11 and 13, and LT10), having variable salinity levels between 11.5 and 33.7 (Table 2), but it was most abundant in sample 13. The diatom flora of this sample included Melosira spp. and several unidentified Navicula taxa in larger numbers., Published as part of Zidarova, Ralitsa, Haan, Myriam De, Ivanov, Plamen, Hineva, Elitsa & Vijver, Bart Van De, 2022, The genus Craspedostauros E. J. Cox (Bacillariophyta) on the coasts of Livingston Island, Maritime Antarctica, pp. 1-24 in Phytotaxa 572 (1) on pages 4-7, DOI: 10.11646/phytotaxa.572.1.1, http://zenodo.org/record/7305672

Craspedostauros confusus Zidarova, M.de Haan, P.Ivanov, Hineva & Van de Vijver sp. nov. (Figs 9– 6, 8, 8–56) Description LM observations (Figs 9– 6, 8):— Frustules lanceolate in girdle view with convex, rarely weakly constricted (and hence biarcuate) margins, bearing numerous copulae. Longer valves linear with broadly rounded apices (Fig. 19), becoming narrowly lanceolate to elliptic-lanceolate in smaller valves with more cuneately rounded (Figs 21, 22), sometimes almost subrostrate apices (Fig. 23). Valve margins weakly convex (Fig. 21) to almost straight in the middle (Figs 20, 22, 24), lacking any constriction. Valve dimensions (n = 16): length 22.0–49.5 µm, width 4.5–6.5 µm. [Valves (n = 27) observed in other populations on Livingston Island during the study (Figs 60–77, 79) had a valve length of 18–50 µm and a valve width of 4.0–6.5 µm]. Axial area very narrow, linear (Figs 19–24, 28). Central area narrow, forming an almost rectangular (Fig. 19) to bow-tie-shaped fascia (Figs 20–24, 28), widening towards the valve margins. Raphe filiform, straight (Fig. 19) to weakly undulating, with expanded central raphe endings, and elongated terminal raphe fissures, unilaterally weakly bent (Figs 21, 24, 28). Striae rather coarse, parallel to occasionally very weakly radiate in the middle (Fig. 22), parallel to very weakly convergent near the apices (Figs 19, 24), 22–24 in 10 µm. Areolae, at least the larger ones bordering the axial area, weakly discernible in LM (Fig. 19). SEM observations (Figs 8–56):— Valve face weakly domed, with a deep mantle (Figs 48–51). External raphe branches straight with weakly undulating (Fig. 49) to straight (Fig. 51) central raphe endings, terminating in drop-like expanded pores (Figs 49, 51). Terminal raphe fissures continuing shortly onto the mantle, unilaterally hooked (Figs 48, 51). Axial area triangularly expanded at the apices, bearing a silica flap on one side, covering the terminal raphe fissures (Fig. 50). Striae uniseriate, composed of cribrate, rounded to elliptic areolae. Near the raphe areolae clearly larger (Figs 49, 50 and Figs 88–90). Cribrum structure of the areolae bordering the axial area possessing four to seven peripheral pores, and two to three central pores. All other areolae with cribra composed of 2–5 peripheral pores, lacking central pores (Figs 49, 50). Areolae continuing around the apices (Figs 48, 50), ca. 25–30 in 10 µm. Internal areolar openings rounded to elliptic (Figs 53–56). Internal raphe straight, located on a distinct sternum (Figs 52, 53). Central raphe endings terminating onto double helictoglossae (Figs 53, 55). Terminal raphe endings finish onto broad helictoglossae. Stauros narrow, located on a wider hyaline fascia (Figs 52, 53, 55). Type:— ANTARCTICA. South Shetland Islands: Livingston Island, Hannah Point, sample 14 (62° 39’13” S, 60° 36’ 41” W), marine epilithon, R. Zidarova, 16th December 2018 (holotype BR-4760! = Fig. 28, isotype Slide 417! (University of Antwerp, Belgium)). Etymology:— The species epithet, confusus, Latin for confusing, reflects the complex taxonomic history of the genus Craspedostauros in the Antarctic Region, and the possible long-term inclusion of this species within the more common Antarctic species C. laevissimus. Ecology and associated diatom flora:— Craspedostauros confusus sp. nov. was found as abundant in the epilithon of several tidal pools at Hannah Point (sample 14, type), Mongolian (Reserve) Port (samples DNA5 and MO’), and Caleta Argentina (sample LT6). The salinity level in the pools (when measured) ranged between 33 and 35 PSU (Table 1), and their diatom flora was dominated by various species, including Navicula spp., Melosira spp., Parlibellus sp., Tabulariopsis australis (Peragallo 1921: 67) D.M. Williams (1988: 249) and Tripterion margaritae (Frenguelli & Orlando 1958: 98) L.F. Fernandes & Sar (2009: 67).

Based on light and electron microscopical investigations, a new genus Craspedostauros is described for a group of marine biraphid diatoms previously placed in Stauroneis Ehrenberg. The genus Stauronella Mereschkowsky had been erected for one of these species, Amphiprora constricta sensu W. Smith, but Mereschkowsky's name cannot be used for nomenclatural reasons. Craspedostauros species can be recognized by the possession of cribrate areolae, a stauros that is usually narrower than the fascia, many girdle bands with double rows of cribrate areolae and two chloroplasts, fore and aft of the central cytoplasm, each with a central pyrenoid. The genus shows similarities in its pore structure and chloroplast type and arrangement to Mastogloia Thwaites ex W. Smith and Aneumastus Mann & Stickle, suggesting that it is more closely related to these than to other naviculoid genera with a stauros, i.e. Stauroneis, Staurophora Mereschkowsky, Meuniera Silva and Haslea Simonsen. The stauros is a feature that probably aro...