The genus Afrocymbella (Bacillariophyceae) from lakes Malawi and Tanganyika, with description of new fossil and extant species Author Stone, Jeffery R. 0000-0002-1313-0643 Indiana State University, Department of Earth and Environmental Systems, Terre Haute, Indiana, U. S. A. & jeffery. stone @ indstate. edu; https: // orcid. org / 0000 - 0002 - 1313 - 0643 jeffery.stone@indstate.edu Author Wilson, Mallory C. 0000-0002-2852-125X Indiana State University, Department of Earth and Environmental Systems, Terre Haute, Indiana, U. S. A. & mwilson 108 @ sycamores. indstate. edu; https: // orcid. org / 0000 - 0002 - 2852 - 125 X mwilson108@sycamores.indstate.edu Author Jovanovska, Elena 0000-0002-3413-3683 Senckenberg Research Institute, Department of Paleoanthropology, Frankfurt am Main, Germany & jovanovska. eci @ gmail. com; https: // orcid. org / 0000 - 0002 - 3413 - 3683 jovanovska.eci@gmail.com text Phytotaxa 2022 2022-08-01 556 1 21 48 http://dx.doi.org/10.11646/phytotaxa.556.1.3 journal article 111190 10.11646/phytotaxa.556.1.3 ac636d2a-3e29-49a7-a37c-a44fb4e0e878 1179-3163 6951967 Afrocymbella nyassae sp. nov. (LM Figs 32–53 , SEM Figs 54–59 ) Description:— Valve length 20–30 μm, valve breadth 7–10 μm. Length to breadth ratio: 2.8. Valves distinctly dorsiventral and heteropolar, semirhomboid-lanceolate ( Figs 32–59 ). Dorsal margin distinctly arched, ventral margin with gibbous center portion, though otherwise slightly convex ( Fig. 55 ). Valve apices with rostrate and nearly symmetrical poles ( Figs 32–53 ). Internally, valve apices bear small to indistinguishable pseudosepta ( Fig. 59 ). APF of round poroids present at footpole ( Fig. 56 ), surrounded internally by knobby jointed ridge of silica (white arrow in Fig. 59 ). Axial area narrow, dorsal margin slightly curved ( Figs 32–53 , 55 ). Central area round, slightly asymmetric, wider on dorsal side ( Figs 32–53 , 54 ). Single stigmoid present on dorsal side of central nodule, externally circular to transapically elongated ( Figs 54, 55 ), internally elongated slit ( Figs 57, 58 ). Raphe curved and slightly sinusoidal ( Figs 54, 55 ). External proximal raphe ends expanded into small pores dorsally deflected ( Figs 54, 55 ), internally covered by nodular or flap-like silica development ( Figs 57, 58 ). External distal raphe terminal fissures ventrally deflected ( Figs 55, 56 ), internally slightly elevated into small lobed helictoglossa at some distance from valve apices ( Figs 57, 59 ). Striae radiate throughout, uninterruptedly continuing onto valve mantle ( Fig. 55 ), 14–16 in 10 μm at middle; 18 in 10 μm at valve apices. Striae composed of 30–35 lineate to slit-like areolae in 10 μm, internally ellipsoid without velum ( Fig. 57 ). Type:— REPUBLIC OF MALAWI . Lake Malawi central basin, Core MAL05-1 C, Drive 26E2; mud, sampled at 17–18 cm ; composite 83 m depth (corresponding to ~135.5 ka), 11°17’39.6” S 34°26’09.0” E , J. R . Stone, 22 nd May 2006 ( holotype designated here, circled specimen ANS-GC17194! = Fig. 39 , isotypes circled specimens ANSGC17195 !, BM-101978! Cleaned type materials: ANS-GCM 33026. Registration: https://zoobank.org/NomenclaturalActs/13f4f4e3-74e6-41ba-bd38-a84665cfacd3 Etymology:— The species name ‘ nyassae ’ refers to the type locality, Lake Malawi (aka Lake Nyassa). Distribution:— To date, Afrocymbella nyassae sp. nov. has only been observed from sediment assemblages of Lake Malawi ranging from ~140 ka to 90 ka in the MAL05-1C drillcore (1C, Fig. 1 ). It is likely an extinct species, seemingly without extant populations.