Valves are discoid, flat with a short down-turned mantle, diameter 12– 34 μm. Areolae on valve face are consistent in size and weakly arranged in curved rows. Areolae on the mantle are consistent in size and smaller than areolae on the valve face (Fig. 6, A). Foramen are located on the external wall of loculate areolae, elliptic velum is located on the internal wall (Fig. 6, F & G). A single row of compactly spaced fultoportulae encompasses the valve at the junction of the valve face and margin. Internal structure of the fultoportulae are raised and exhibit small struts that extend into four satellite pores. Externally the fultoportulae are raised ~1 μm from valve face and are covered in granules (Fig. 6, B & D). A single rimoportula is associated with fultoportulae that are slightly displaced toward valve center (Fig. 6, C).

Type: — West Turkana Kaitio, northwestern Kenya, (4.109722° N, 35.871781° E) Pleistocene lake sediment core of the Natoo Member of the Nachukui Formation sediment core (HSPDP-WTK13-1 A) material, sediment depth ~ 60 meters below surface, collected by Feibel, C., Cohen, A., & Beck, C., July 2013, holotype, designated here; deposited in ANSP! (Circled specimen on slide WTK 179, illustrated herein as Fig. 5, B).

Etymology: — Thalassiosira feibelii is named in honor of Dr. Craig Feibel for his outstanding contributions to understand early hominin-environmental relationships in the Tukana Basin, Kenya.

Remarks:— Thalassiosira feibelii is remarkably similar to T. faurii (Gasse) Hasle (1978: 282), the most notable difference is that T. feibelii does not exhibit central fultoportulae while T. faurii is characterized as having three central fultoportulae separated by °120, being midway from valve center to valve margin.