Table 4. Comparison of Pseudostaurosira frankenae sp. nov. with selected, similar, congeneric, and cruciform to broadly lanceolate taxa. Features in bold italic font are defining for each taxon. *Internal view of P. caballeroae is unknown. Feature/speciesP. australopatagonica M.L. García, L.A. Villacís, Maidana & E. MoralesP. caballeroae V.H. Salinas, D. Mora, R. Jahn & N. Abarca *P. decipiens E. Morales, G. Chávez & EctorP. frankenae sp. nov.P. laucensis Lange-Bertalot & RumrichP. parasitica (W. Smith) E. MoralesP. pseudoconstruens (Marciniak) D.M. Williams & RoundValve dimensions (µm)L: 20-25 W: 6.5-9.0L: 13.8-17.7 W: 6.9-8.5L: 4-29 W: 4-6L: 8.7-12.0 W: 6.7-7.7L: 5.5-20.0 W: 3.5-5.5L: 9-18 W: 4.5-5.0L: 4-22 W: 3-7Stria density (in 10 µm)10-1213-1413-151414-1519-2115-18Valve outline; axial area; virgaeCruciform to rhomboid with subcapitate apices; lanceolate, wider at central area, clearly depressed with respect to virgae in outer view, slightly depressed in internal view; much wider than striaeCruciform with narrowly rounded ends; lanceolate, wider at central area; clearly depressed with respect to striae in external view; wideLanceolate with rostrate ends; lanceolate wider at central area, externally slightly depressed with respect to virgae, internally at the same level as the latter; wideCruciform with broadly rounded ends; lanceolate, wider at central area; clearly depressed with respect to striae in external and internal view; slender than striaeLanceolate to rhomboid with narrowly subrostrate to cuneate ends; lanceolate, faintly depressed with respect to virgae in outer view, flat in internal view; wideLanceolate with narrowly rounded to subcapitate ends; lanceolate, wider at central area, clearly depressed with respect to virgae in external and internal view; as wide as striaeCruciform with broadly rounded to subcapitate ends; lanceolate wider at central area, slightly depressed with respect to virgae in external and internal view; much wider than striaeAreolae; volae; striaeRound at apices to elliptically elongate; large generally growing opposite from shorter axis of areolae, internally forming a dendritic pattern; composed of 1-2 areolae on valve face, 1 large, round to ovoid on valve mantleRound at apices to elliptically elongate, sometimes only 1 very long on valve face; smaller, bifurcate and growing from longer areolar axis; composed of 1-2 areolae on valve face, valve mantle areola not clearly illustratedRound to ovoid; diapason shaped and further bifurcate at the valve interior, allowing the internal deposition of two concentric disks of inorganic material; composed of 1-2 areolae on valve face and 1 large, trapezoid on mantle, sometimes an extra round one present on mantleRound to elliptic; smaller, bifurcate, allowing the internal deposition of an elliptic disk of inorganic material; composed of 1-4 areolae on valve face and a single, large, trapezoid one on mantleRound to elliptic; developed with ring-like depositions distorted in different ways at the valve interior; composed of 1-2 areolae on valve face, decreasing in size toward axial area and a single, slightly larger, elliptic to trapezoid on the mantleRound at apices to elliptically elongate; small, usually originating from smaller axis of valve; composed typically of 1, unusually 2, areolae on valve face, typically one smaller areola on valve mantleRound to elliptic; smaller, bifurcate, originating from inner areolar perimeter; composed of 1-4 areolae on valve face, 1-2 on valve mantle, of same size as valve face areolaeSpines; stipules; flapsIncipient, forming a short arch-like structure extending from virgae to virgae; absent; absentVery thin, flattened, extending from virgae to virgae, forming an undulate to dentate pattern on valve face/mantle transition; absent; absentSolid, elliptic base, as wide as basal vimen, flattened body with concave sides, spatulate or heart-shaped tip; absent; absent, only mineral depositions resembling floating disks on outer areolar openingSolid, round to elliptic base, wider than basal vimen, triangular in side view, flattened upper body with bifurcate tip; absent; disk-like, 1 persistent in valve face areolae; 1-3 in mantle areolaeIncipient and occurring as whitish depositions along valve face/mantle transition; absent, absentAbsent; absent; absentSolid, with long elliptic base, shorter than basal virgae on which they grow, flattened body with concave sides, highly branched tips; absent; absentApical pore fields; mantle abvalvar blistersCavernous and large, almost covering entire valve apex with poroids at the base of troughs, internally opening into a single elliptic depression; small, absent from the apicesCavernous and large, almost covering entire valve apex with poroids at the base of troughs, internally unknown; excess depositions impede visualization in original illustrationsCavernous, from 1 to several rows of poroids can be seen externally, internally a roundish depression contains several rows or poroids; developed, present including at valve apicesCavernous, only one transapical row of poroids can be seen externally, internally, a round depression contains various rows of poroids; developed, present including at valve apicesNon-cavernous, sunken onto valve apex in external view, internal view unknown; small, not covering apicesCavernous, visibly sunken onto valve apex and occupying almost its entirety, pores lie at bottom of troughs, internally plaque of pores is raised; very small and absent from apicesVery reduced externally, internally opening into a small depressed circular area; small and present at apicesReferencesGarcía et al. (2021)Salinas et al. (2020)Morales et al. (2012b)This studyServant-Vildary (1986), Rumrich et al. (2000)Morales (2003a, 2010)Williams and Round (1987)

Published as part of Morales, Eduardo A., Wetzel, Carlos E. & Ector, Luc, 2021, New and poorly known " araphid " diatom species (Bacillariophyta) from regions near Lake Titicaca, South America and a discussion on the continued use of morphological characters in " araphid " diatom taxonomy, pp. 23 in PhytoKeys 187 on page 23, DOI: 10.3897/phytokeys.187.73338