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Electronic Flora of South Australia Genus Fact Sheet

Genus PSEUDOLITHODERMA Svedelius ex Kjellman & Svedelius 1910: 175

Phylum Phaeophyta – Order Chordariales – Family Ralfsiaceae

Reproduction: Reproduction by plurilocular or unilocular sporangia borne on the terminal cell of erect filaments, with one or four unilocular sporangia on each terminal cell.

Life history uncertain: possibly diplohaplontic and isomorphic, but probably direct in some taxa.

Type species: P. extensum (Crouan & Crouan) Lund 1959: 84 [Syn. P. fatiscens (Kuckuck) Svedelius ex Kjellman & Svedelius 1910: 176, fig. 99 (NON Lithoderma fatiscens Areschoug)].

Taxonomic notes: Thallus a few mm to several cm across, crustose and relatively thin (0.2–1 mm thick), usually firm, surface smooth, gelatinous or not, firmly adherent to the substratum, without rhizoids. Basal layer of radiating filaments, becoming 2–4 cells thick, each cell of the upper layer producing an erect filament. Erect filaments either adhering laterally under pressure or separating relatively easily from each other, cylindrical, with short cells. Phaeophycean hairs present or absent. Phaeoplasts discoid to laminate, several per cell, without pyrenoids.

A genus of some 6 species (Sears & Wilce 1973, p. 81; Tanaka & Chihara 1981, p. 377), largely confined to the North Atlantic Ocean. The species described below is apparently the first from the Southern Hemisphere, though Lithoderma piliferum Skottsberg (1921, p. 19, fig. 8e-m) may be a Pseudolithoderma. Pseudolithoderma differs from Lithoderma Areschoug (1875, p. 22) which has lateral plurilocular sporangia and from Petroderma Kuckuck (1897, p. 382) which has only one phaeoplast per cell. However, distinctions between these genera are not always clear, e.g. the type species of Pseudolithoderma has the erect filaments tightly associated and not separating under pressure [as also do P. roscoffensis Loiseaux (1969, p. 308), P. subextensum (Waern) Lund and P. nigra Hollenberg], but P. rosenvingii (Waern) Lund and P. paradoxum Sears & Wilce have a softer thallus with the erect filaments separating easily. This latter character is a feature of Petroderma, which is then separated from Pseudolithoderma by the presence of a single phaeoplast per cell.


ARESCHOUG, J.E. (1875). Observationes Phycologicae, III. Acta Reg. Soc. Sci. Upsala, Ser. III, 10, 1–35, Plates 1–3.

KJELLMAN, F.R. & SVEDELIUS, N. (1910). Lithodermataceae. In Engler, A. & Prantl, K. (Eds). Die natürlichen Pflanzenfamilien, Nachträge zum I T., 2 Abt., 173–176.

KUCKUCK, P. (1897). Bemerkungen zur marinen Algen-vegetation von Helgoland II. Wiss. Meeresunters. Abt. Helgol., N.F. 2, 373–400.

LOISEAUX, S. (1969). Sur une espèce de Myriotrichia obtenue en culture à partir de zoides d'Hecatonema maculans Sauv. Phycologia 8, 11–15.

LUND, S. (1959). The marine algae of East Greenland. I. Taxonomical part. Medd. Grønland 159(1), 1–247.

SEARS, J.R. & WILCE, R.T. (1973). Sublittoral benthic marine algae of southern Cape Cod and adjacent islands: Pseudolithoderma paradoxum sp. nov. (Ralfsiaceae, Ectocarpales). Phycologia 12, 75–82.

SKOTTSBERG, C. (1921). Botanische Ergebnisse der Schwedischen Expedition nach Patagonien und dem Feuerlande, 1907–1909. VIII. Marine Algae. I. Phaeophyceae. K. Svenska Vetenskapsakad. Handl. 61(11), 1–56.

TANAKA, J. & CHIHARA, M. (1981). Taxonomic study of the Japanese crustose brown algae (6). Pseudolithoderma (Lithodermataceae, Ralfsiales). J. Jap. Bot. 56, 376–381.

The Marine Benthic Flora of Southern Australia Part II complete list of references.

Author: H.B.S. Womersley

Publication: Womersley, H.B.S. (14 December, 1987)
The Marine Benthic Flora of Southern Australia
Part II
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