Table 2.
Comparison of morphological features of Gomphonema baicalodemersum sp. nov. and related species.
| G. baicalodemersum sp. nov. | G. medioasiae | G. demersum | |
|---|---|---|---|
| Outline | slightly heteropolar, rhombic lanceolate (in larger specimens), or very slightly clavate (in smaller specimens) | only very slightly clavate but almost naviculoid symmetrical to the transapical axis since head poles appear weakly broader than basal poles and lateral margins gradually taper to the poles | lanceolate, only very slightly gomphonemoid-cuneate |
| Headpole | acutely rounded | acutely rounded | obtusely rounded |
| Footpole | acutely rounded | acutely rounded | narrower than headpole |
| Axial area | lanceolate, widening at the central area | barely or not separated appearing lanceolate | lanceolate, widening at the central area |
| Central area | weakly expressed | barely or not separated appearing lanceolate | broad rhombic lanceolate |
| Valve length (μm) | 14.5–38.5 | 47–52 | 13–41 |
| Valve breadth (μm) | 3–6 | 6–8 | 3.6–6.0 |
| Striae number in 10 μm | 11–15 | 8–11 | 12–16 |
| Areolae number in 10 μm | ≈30 | 16–18 | ≈30 * |
| Isolated pore type | externally, the circular opening located near the central nodule; internally, large, transversely elongated, and located in a long groove, turning into foraminal rows | located near the central nodule and densely spaced to the rather long median stria | the circular external stigma opens internally in an elongated pore |
| Distribution | Russia. Baikal | Mongolia | Russia. Baikal |
| References | This study | [50] | [44] |
* Counted from published data.