Observations on the marine benthic diatom Halamphora yundangensis W.W.Wu et al., a species originally described from China, in the Mediterranean Region

During light and scanning electron microscope observations of marine benthic diatoms on various substrates in the eastern Adriatic Sea and the western Black Sea, we discovered a peculiarly structured amphoroid diatom species. The species was characterised by semi-elliptic to semi-lanceolate valves with distinctly protracted capitate to occasionally rostrate apices, a dorsal valve side crossed by transapical slits, a wide dorsal marginal ridge, biseriate dorsal striae internally, and usually lacking ventral striae externally, except for one or two poroids at the apices. Following a search in the literature, this taxon could only be identified as Halamphora yundangensis, a recently described species from the southeastern coasts of China. Here we present the first verified observation of this species in the Mediterranean Region. After thorough analyses of the observed populations in scanning electron microscopy and a literature overview, we provide an emended description of the species, and additional information enabling/justifying its separation from similar taxa occurring in the Mediterranean Region. Notes on the ecology and distribution of the species based on the new observations are also given.