Cyclotella stoermeri Khursevich & Kociolek, 2013

Kociolek, J. P. & Khursevich, G. K., 2013, Morphology of some fossil lacustrine centric species from the western United States assigned to the genus Cyclotella (Bacillariophyta), including four described as new, Phytotaxa 127 (1), pp. 81-99 : 90-92

Cyclotella stoermeri Khursevich & Kociolek , sp. nov. ( Figs 40–55 )

Type:— USA. Oregon: Klamath County, Sprague River, Drews Road, diatomite, (Circled specimen ( Fig. 40 ) on CAS Slide #433091, material CAS Accession Number 600179 ( CAS !), holotype, designated here).

Additional material examined:— Oregon, Klamath County, Sprague River, Drews Road, CAS Accession Numbers 600175, 600176, 600181, 701883, Slide Number 1026029 ( CAS !).

Description: —Frustules solitary, round or circular in valve view, 7–100 µm in diameter, short cylindrical in girdle view with several intercalary bands. Valve face is nearly flat. The valve center has one-several areolae surrounded by hyaline ring, rarely it is structureless. Central area contains loculate areolae with internal domed cribra and external foramina, arranged in more or less short radial rows (from 2 to 17 small areolae in row). Central area fultoportulae have never been observed. The striated zone occupies 1/2 to 3/4 the length of the valve radius. Striae, 7–12 in 10 µm, are radial, of unequal length, slightly undulate towards the center of the valve. They consist of two rows of small puncta on the valve face surface and of three-five small puncta on the valve margin. The striae are divided by costae dichotomously branched from the central area towards the valve margin. Alveolae are complex and simple. Marginal fultoportulae with three satellite pores are located on all recessed costae within marginal chambers. They are represented by small openings externally. One-several raised rimoportulae are positioned also on the recessed costae internally. They are marked by small round apertures on the external valve surface. Solid conic spines are present irregularly at the valve face/mantle junction.

Remarks: — Cyclotella stoermeri differs from C. elgeri Hustedt (1952: 374 , fig. 31) by the wider striated zone, the smaller central area, as well as by the different structure and location of marginal fultoportulae (they have two satellite pores and are placed on all thick costae on the mantle in C. elgeri , while marginal fultoportulae in C. stoermeri possess three satellite pores and occur only on thin recessed costae). This species is dedicated to our friend and colleague, Dr. E.F. Stoermer of the University of Michigan, Ann Arbor.

Figures

FIGURES 40–49: Cyclotella stoermeri. LM. Valve views showing size diminution series. Note dissimilar lengths of striae. Fig. 40. Holotype. Scale bar = 10 µm.

FIGURES 50–55: Cyclotella stoermeri. SEM. Figures 50–52. External valve views. Fascicles are comprised of 1–3 rows of small areolae. The ribs are thickened and elevated, becoming thinner on the valve mantle. The valve center has enlarged areolae. Scale bars = 10 and 3 µm, respectively. Figures 53–55, internal valve views. Complex and simple alveolae are positioned around the perimeter of the valves. Thick and thin costae are evident, and marginal fultoportulae are evident on the recessed costae. Rimportulae are positioned also on the recessed costae. Areolae with domed cribra are evident in the center of the valves. Scale bars = 3, 2 and 1 µm, respectively.