Platichthys Lange-Bertalot, Kulikovskiy, Witkowski, Seddon & Kociolek 2015, gen. nov.
Creators: name: Lange-Bertalot, Horst
name: Witkowski, Andrzej
name: Seddon, Maxim S. Kulikovskiy Alistair W. R.
name: Kociolek, John P.
Publisher: name: Zenodo
Year: 2015
Subjects: Biodiversity
Taxonomy
Animalia
Chordata
Pleuronectiformes
Pleuronectidae
Platichthys

description: Platichthys Lange-Bertalot, Kulikovskiy, Witkowski, Seddon & Kociolek, gen. nov.   
 LM (Figs 1–18, 39–49): cells solitary. Plastids currently unknown. Frustules lying exclusively in girdle view, linear-elliptical to linear with broadly rounded ends. Between both valves the girdle consists of several barely recognizable copulae. Prominent fibulae, approximately developed as circular structures are apically arranged at some distance below the frustule margins. In straight view the fibulae lie on the same level in both valves. Consequently a “nitzschioid” or “hantzschioid” symmetry classification (i. e. raphe on the same or opposite sides, respectively) becomes obsolete. Valve ends appear slightly rostrate in an appropriately oblique position. Transapical striae, areolae, raphe canals or raphe slit are not discernible, sometimes phase contrast optics allows observation of the central nodule and the apical raphe endings. EM, valve exterior (Figs 19–29, 50–59): the shape of the frustules resembles a flat tongue when the valves are separated from each other, or a cigar when the valves are connected through the girdle bands. The girdle is composed of numerous open, porous copulae. The valve face is steep and compressed laterally to form a narrow keel. Below the keel, around the mid-width, the valve becomes broader. The valve mantle is developed as a very narrow, structureless rim. The raphe runs within a well-separated, structureless axial area with two raphe branches separated by a narrow central nodule. External central raphe endings are relatively simple, slightly expanded, whereas the apical external endings are bent in the same direction. In a hypothetical cross-section of a frustule, the position of both valves is roughly like two hairpins lying opposed with the open ends connected, and the raphe canals are situated at the closed ends. Transapical striae uniseriate, very densely spaced, far beyond the resolution power of LM. The areolae are simple, sometimes, slightly transapically elongate pores. SEM, valve interior (Figs 33–38, 59, 60): internally the fibulae are column-shaped, short and arched. They separate the raphe canal from the major part of the valve lumen (cavity). The fibulae are positioned at some distance from the raphe. As the fibulae are large, usually a few striae merge into one fibula. Wave crests begin at the basis of fibulae while wave troughs continue into the interfibula spaces (portulae). The portulae are very simple and are formed as a result of a slight broadening of the base of the fibulae. Internally, the raphe slit is straight, the two raphe branches are separated by a narrow central nodule, whereas at the apices they terminate in a small helictoglossa. Internally, the areolae are positioned in shallow depressions formed by the virgae.   
 Type:— Platichthys krammeri Lange-Bertalot & Kulikovskiy, sp. nov. (see below).   
 Etymology:—the Greek name of the genus is similar to the scientific name of the flat-fish Platichthys flesus (flounder) and refers to the roughly comparable shape and symmetry of the valve and frustules respectively.   
 Comments: —One salient feature of Platichthys gen. nov. is the stabilization of very thin cell walls by, as seen as alternating wave crests and wave troughs in the SEM, whereas the crests can easily be mistaken for prolongations of the fibulae with LM microscopy. This is known from the “light construction” of the valves of Surirella (Krammer & Lange-Bertalot 2004) and is also observed in Platichthys gen. nov. Striae- and areolae- densities are uncommonly high in comparison with other canal raphe diatom genera, except Entomoneis.
description: Published as part of Lange-Bertalot, Horst, Witkowski, Andrzej, Seddon, Maxim S. Kulikovskiy Alistair W. R. & Kociolek, John P., 2015, Taxonomy, frustular morphology and systematics of Platichthys, a new genus of canal raphe bearing diatoms within the Entomoneidaceae, pp. 135-149 in Phytotaxa 236 (2) on page 137, DOI: 10.11646/phytotaxa.236.2.3, http://zenodo.org/record/13630533