Lamprothamnium sardoum R.Becker, sp. nov. (Figs 1–3) Type:— ITALY. Sardini, circa San Giovanni Sinis, in aquis stag., 39°53’13 N, 8°26’22 E, WGS 84, 05 April 2018, Becker 2018 (Herb. ROST). The monoecious plants are small to medium–sized (9–17 cm including the protonema), light green, opaque and not incrusted, with well developed, long stipulodes and bract-cells (Fig. 1 B, C). The bright orange gametangia are clustered inside and outside the base of the whorl and on the lowest branchlets (Fig. 2B), and are abundant and obvious, even in situ in the habitat (Fig 2A). Plants grow as individual shoots, fertile at nearly all nodes, with long whispy protonemal axes longer than the height of the plants (Fig. 1B). Axes narrow, 350–600 µm in diameter (usually 375–550 µm), ecorticate, internodes 1–3.2 cm long except in the apicies. Stipulodes, up to one per branchlet (but frequently replaced by gametangia; Fig. 1A), up to 1.75 mm long, downward and outward pointing where present. Branchlets 5 to 8 in a whorl, up to 1.8 cm long, basal branchlet cell short on fertile branchlets, up to 2 mm long (Fig. 1C), sterile branchlets not seen. Branchlet end segments usually 1 cell, up to 750 µm long, mucronate (Fig. 2D). Bract cells verticillate (4 or 5 around) on the lowest two or three branchlet nodes in fertile whorls, up to 1.7 mm long (Fig. 2C). Gametangia clustered inside and outside the base of the whorl and conjoined, geminate or geminate-conjoined on the lowest 2–3 branchlet nodes (Fig. 1A). Oogonia bright orange (Fig. 2B), apparently sessile, clustered inside and outside the base of the whorl, and when occurring on the branchlets, usually conjoined with antheridia, below or beside the antheridium, 500–750 µm long, 400–600 µm wide (only dry material was measured), with 10–14 convolutions (Fig. 1D). Coronula 75–110 µm long, 130–150 µm wide, coronula cells oval-shaped (Fig. 1E). Oospores black, 510–650 µm long, 250– 475 µm wide at the widest point, with 9–11 striae of low ridges, ornamentation smooth (Fig. 3, Fig.2E). Antheridia 325–450 µm in diameter, orange, solitary or conjoined with oogonia on the branchlets (Fig. 1D), as well as inside and outside the base of the whorl. Vegetative reproduction not known. Chromosomes not known. Etymology: The specific epithet is named for the island of Sardinia where collection was made.

Published as part of Casanova, Michelle T. & Becker, Ralf, 2022, Lamprothamnium sardoum sp. nov. (Characeae, Streptophyta): A new species of Lamprothamnium for Europe, pp. 269-277 in Phytotaxa 567 (3) on pages 271-272, DOI: 10.11646/phytotaxa.567.3.6, http://zenodo.org/record/7156708