Table 1.

Morphological characteristics of Naviculacongqiancuoensis sp. nov. and morphologically related species.

	N.congqiancuoensis sp. nov.	N.angustaGrunow (1860: 528)	N.leptostriataJørgensen (1948: 59)	N.pierceiBahls (2012: 28)	N.heimansioidesLange–Bertalot (1993: 113)
Outline	Linear to linear-lanceolate	Linear	Narrowly lanceolate	Linear and subtly triundulate with a distinctly tumid middle	Lanceolate to linear-lanceolate
Ends	Broadly rounded	Slightly protracted ends	Acutely rounded, subtly protracted apices	Broadly rounded, somewhat wedge-shaped apices	Slightly drawn-out ends
Axial area	Narrow and linear	Narrow	Narrow	Very narrow and linear	Narrow
Central area	Slightly widening	Moderately asymmetrical, wedge-shaped or irregularly shaped	Small, transversely widened, and asymmetrical with irregular borders.	Elliptical and asymmetric, bordered by 2–5 irregularly shortened and often faint striae.	Small
Valve length (μm)	42.7–51.2	42.0–58.0	33.0–39.0	64.0–76.0	18.7–39.3
Valve width (μm)	4.9–6.1	6.0–7.0	4.9–5.7	6.8–8.0	5–6
Striae in 10 μm	18–20	12–13	19–20	11–13	14–16
Areolae in 10 μm	50	32	Not given	30	Not given
Distribution	Lake Congqiancuo, Haizishan Nature Reserve, Daocheng County, Sichuan Province, China	Widely distributed	Northern Rocky Mountains, where it is typically associated with Navicula notha.	Copper Lake in Shoshone County, northern Idaho	Widely distributed
Reference	This study	Grunow 1860, Lange-Bertalot 1996	Jørgensen 1948, Lange-Bertalot H 2001	Bahls 2012	Lange–Bertalot 1993, Taylor 2016