Pantocsekiella elgygytgynensis, Luethje & Snyder, 2021

Luethje, Melina & Snyder, Jeffrey, 2021, Climate-related morphological changes in Pantocsekiella (Mediophyceae) spanning 0 - 1.2 Ma in the Lake El’gygytgyn, northeastern Russia including Pantocsekiella elgygytgynensis sp. nov., Phytotaxa 478 (1), pp. 67-91 : 85

Pantocsekiella elgygytgynensis sp. nov.

Figs. 17–30 , 43–44 , 51–52 , 59–64 , 67–70

Description:

Valves circular, valve faces nearly flat. Valve diameter (n = 139): 3.8–21.3 µm in SEM, 3–24 µm in LM. Initial valves dome-shaped, 9–27 µm in diameter ( Figs. 24 , 30 , 70 ). Central area of valve flat to radially undulate, smooth to colliculate. Central area 25–75% of the valve diameter. Radial orbicular depressions 3–6 in number, occasionally with many fovi (small depressions). Central fultoportulae clustered within radial orbicular depressions and fovi. A single rimoportula present near marginal striae, approximately 0.8–5.2 µm from valve margin. Rimoportula distance from the valve margin 15–40% of the valve diameter. Marginal fultoportulae openings visible externally and internally, every 3–6 costae. Striae multiseriate composed of two outer rows of large areolae and 1–3 inner rows of small areolae. Striae density irregular, 12–25 striae /10 µm, with a mean of 18 striae/10 µm. Internally, valve face flat. Central fultoportulae 1–22 in number. Central fultoportulae robust, appearing as short tubules with 2–3 satellite pores. Costae bearing marginal fultoportulae slightly depressed. Internal openings of marginal fultoportulae with 2 satellite pores. The single rimoportulae visible as a sessile labium with a wide slit with variable orientation.

Etymology: The species named here (elgygytgynensis) has only been observed in the Lake El’gygytgyn sedimentological record and is therefore named after the lake.

Type locality: Lake El’gygytgyn, Russia, material from the Lake El’gygytgyn Scientific Drilling Project composite core 5011-1 and LZ1024

Holotype: Composite core 5011-1, sample DC570 (424.1 ka), ANSP GC 36369 , slide housed at the Diatom Herbarium , National Academy of Sciences, Drexel University, U.S ( Fig. 19 ).

Isotypes: ANSP GC 36370, slide housed at the Diatom Herbarium, National Academy of Sciences, Drexel University, U.S, and CANA 128930, slide housed at the Canadian Museum of Nature, Canada.

Taxonomic notes:

Pantocsekiella elgygytgynensis shares the circular valve shape, the flat valve face, the arrangement and position of the marginal striae, costae, and rimoportula with other members of the P. ocellata species complex ( Table 2). The newly named species is distinct from other members of the P. ocellata complex in having up to 22 central fultoportulae that are oriented in radial groups, having a larger range in striae density from 12–25, and marginal fultoportulae on every 3–6 costae.

P. elgygytgynensis appears to be similar to the P. ocellata morphology, with a similar size range (5–22 µm for P. ocellata and 3–24 µm for P. elgygytgynensis ), and unequal striae length, a flat smooth to colliculate central area, and 1 rimoportula. However, it differs from P. ocellata in the number of striae in 10 µm (14–20 in P. ocellata and 12–25 in P. elgygytgynensis ), fovi grouped within the depressed concentric undulations, a higher number of central fultoportulae (1–5 in P. ocellata , and 1–22 in P. elgygytgynensis ), central fultoportulae grouped in the depressed concentric undulations, and position of the marginal fultoportulae (each 2–5 costae in P. ocellata and each 3–6 costae in P. elgygytgynensis ).

The new species also resembles P. polymorpha in that both exhibit radial undulation and a variable number of depressions and fovi. However, the two differ in a number of morphological features. They have different valve sizes (4.5–16 µm in P. polymorpha and 4–21 in P. elgygytgynensis ), a different range of striae in 10 µm (20–24 in P. polymorpha and 12–25 in P. elgygytgynensis ), a higher number of central fultoportulae (1–5 in P. polymorpha and 1–22 in P. elgygytgynensis ), different pattern of the central fultoportulae, and a different position of the marginal fultoportulae (each 2–5 costae in P. polymorpha and 3–6 in P. elgygytgynensis ).

P. tripartita valves exhibit radial undulation, are colliculate, and have a similar valve diameter range to P. elgygytgynensis valves. Valves of P. elgygytgynensis can be distinguished from P. tripartita valves by the absence of triangular punctate fields (present in P. tripartita ), different number of striae in 10 µm (19–22 in P. tripartita , and 12–25 in P. elgygytgynensis ), a higher number of central fultoportulae (2–3 in P. tripartita and 1–22 in P. elgygytgynensis ), and the position of the marginal fultoportulae (each 5–7 costae in P. tripartita and each 3–6 costae in P. elgygytgynensis ).

Figures

FIGURES 17– 25: Representative images of the P.elgygytgynensis morphology during MIS Stages 8, 10 and 12. Figs 17–18 & 24) Valves from 440.7 ka (DC620) with initial valve (Fig. 24), Fig. 19) Holotype valve from 424.1 ka (DC570) Figs 20–22, 25) Valves from 351.9 ka (DC460), Fig 23) Valve from 246.6 ka (LZ11-14).

FIGURES 26–30: Representative valves of P. elgygytgynensis from MIS Stages 9 and 11. Fig. 26) Valve from 409.9 ka (DC548), Figs. 27–28) Valves from 401.5 ka (DC536), Figs. 29–30) Valves from 327.3 ka (LZ12-143) with initial valve (Fig. 30).

FIGURES 41–46. Representative external valves from size class 1 (3–5 µm). Fig. 41) Valve from 1.029 Ma (DC1600) showing numerous fovi and two central fultoportulae (cf), Fig. 42) Valve from 952.6 ka (DC1480) showing the rimoportula placement, Fig. 43) Valve of P. elgygytgynensis from 406.7 ka (DC550) showing the rimoportula placement,, Fig. 44) Valve of P. elgygytgynensis from 302.5 ka (LZ12- 54) showing three depressions and three central fultoportulae, Fig. 45) Valve from 119.3 ka (LZ6-60) showing less distinct depressions, and Fig. 46) Valve from 8.28 ka (LZ366) showing P. ocellata morphology.

FIGURES 47–52. Representative external valves from size class 2 (5–10 µm). Fig. 47) Valve from 0.075 ka (LZ23) showing one central fultoportula (cf) and flat valve face with four depressions, Fig. 48) Valve from 29.12 ka (LZ491) showing flat valve face with three depressions, Fig. 49) Valve from 190.5 ka (LZ9-138) showing flat valve face with numerous fovi, Fig. 50) Valve from 198.2 ka (LZ9-155) showing flat valve face with five scattered central fultoportulae (cf), Fig 51) Valve of P. elgygytgynensis from 238.5 ka (LZ10-227), Fig. 52) Valve of P. elgygytgynensis from 417.4 ka (DC570) with white circles highlighting the clusters of central fultoportulae within the large depressions.

FIGURES 59–64. Representative valves from size class 3 (10–15 µm). Fig. 59) external valve of P. elgygytgynensis from 278.8 ka (LZ11- 125), Fig. 60) external valve of P. elgygytgynensis from 333.2 ka (LZ12-176), Fig. 61) external valve of P. elgygytgynensis from 484.1 ka (DC680), Fig. 62) external valve of P. elgygytgynensis from 406.7 ka (DC550), Fig. 63) internal valve of P. elgygytgynensis from 406.7 ka (DC550), Fig. 64) internal valve of P. elgygytgynensis from 302.5 ka (LZ12-54).

FIGURES 65–70. Representative valves of size class 4 (>15 µm). Fig. 65) external valve from 190.5 ka (LZ9-138), Fig. 66) internal valve from 198.2 ka (LZ9-155), Fig. 67) external valve of P. elgygytgynensis from 238.5 ka (LZ10-227), Fig. 68) external valve of P. elgygytgynensis from 406.7 ka (DC550),Fig. 69) internal valve of P.elgygytgynensis from 333.2 ka (LZ12-176), Fig. 70) P.elgygytgynensis initial valve internal view 302.5 ka (LZ12-54).