Surirella lorenyangensis Brindle, Mohan & Stone, 2018

Brindle, Matthew, Mohan, Joseph, Beck, Catherine & Stone, Jeffery R., 2018, Three novel species of Bacillariophyta (Diatoms) in the genera Surirella and Thalassiosira from Pleistocene Paleolake Lorenyang (~ 2 - 1.6 Ma) Turkana Basin, Kenya, Phytotaxa 371 (3), pp. 230-240 : 233-235

Surirella lorenyangensis Brindle, Mohan & Stone spec. nov. ( Figs 3 & 4 )

Valves are heteropolar, ovate, being symmetrical about the apical axis. Foot pole is subrostrate and slightly protracted, whereas the head pole is cuneate to rounded. Valve length ranges between 92–175 μm, widths are 31–43 μm. Distal ends of the median line and alar wings are arched toward the cingulum (base of the apical plane)( Fig. 4 , A). Valve face convex, raised along the median line and covered in granules ( Fig. 4 , E & G). Small poroids are sparse. Raphe positioned in a slightly raised keel along the external margin of the alar wing ( Fig. 4 , F).

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! GC17191 (Circled specimen on slide WTK 173, illustrated herein as Fig. 3 , C) .

Etymology: — Surirella lorenyangensis is named as pertaining to Paleolake Lorenyang, the lake that existed in the Turkana Basin from 2.0 - 1.5 Ma ( Brown & Feibel 1991; Lepre et al. 2007).

Remarks:— Surirella lorenyangensis resembles S. turkanensis Reichardt (1994: 129) by having similar size range and happens to reside in the modern Lake Turkana whereas Paleolake Lorenyang was present in the same basin. S. lorenyangensis differs from S. turkanensis by being heteropolar, exhibiting a distinct headpole and footpole. Terminal raphe ends and alar wings of S. lorenyangensis are also much more down-turned than in S. turkanensis .

Class: Mediophyceae

Order Thalassiosirales

Family Thalassiosiraceae

Thalassiosira

Figures

FIGURE 3. LM Surirella lorenyangensis. Size diminution series of Surirella lorenyangensis Images taken at x400. Scale bar is 30 μm. C is the holotype.

FIGURE 4. SEM Surirella lorenyangensis. Scanning electron micrographs of Surirella lorenyangensis. A nearly complete frustule (A) with both valves and an attached yet broken girdle band (arrowed). Internal structures are smooth (B) exhibiting hollow fibulae. The internal structure of the fibulae are marked by a lattice structure arrowed in (C). The footpole is rostrate (D), while the headpole is more rounded (E). The ala is downturned towards the girdle at both poles (D & E). The raphe is more towards the exterior sides of the ala in the middle of the valve (C & F) and moves to the top of the ala at the poles (D & E). The raphe is contained within a raised channel along the alar wings (F), ala are supported by the fibulae with unobstructed windows between fibulae (F & G). The exterior valve surface is covered in granules arranged weakly in rows, indicated by arrow in (E), also shown in (A & G).