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Pterothamnion francisianum (Wollaston) Athanasiadis & Kraft 1994: 130.

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Pterothamnieae


Platythamnioll francisianum Wollaston 1978: 6, figs 10–14, 18, 19.

Thallus (Fig. 62A) erect, 1–8 cm high, complanately branched with alternate, flexuous, lateral branches (Fig. 61P) mostly every 5–6 axial cells, overtopping previous apices, ecorticate throughout. Attachment by short lateral branches affixed by rhizoids; epiphytic (e.g. on Ballia mariana) or epilithic. Structure. Apical cells 5–7 µm in diameter and L/D 1–1.4, enlarging to 120–230 µm in diameter and L/D 1.5–2.5 in mid thallus and 1–2 in lower axial cells. Axial cells each with 4 whorl-branchlets, first developed unilaterally in curved apices, when mature with 2 opposite major ones 300–700 µm long (often one larger than the other), adaxially branched (Fig. 62B) often with pairs of pinnules (Fig. 61O) (to 90–270 µm long) from the inner rachis cells and single pinnules from the outer cells, larger pinnules sub-branched; minor pinnae 150–250 µm long, simple or with simple pinnules; basal cells of pinnae 20–50 µm in diameter and L/D 1–1.5, tapering to subapical cells 4–8 µm in diameter and L/D 2.5–3.5, apical cells mucronate; gland cells on rachis and pinnule cells, lateral, ovoid to hemispherical, 12–17 µm in diameter. Lateral branches arising from axial cells. Cells uninucleate; rhodoplasts elongate, ribbon like and longitudinal in larger cells.

Reproduction: Gametophytes unknown.

Tetrasporangia (Fig. 61Q, 62B) borne on short branches from cells of pinnules, terminal or lateral, ovoid, 25–35 µm in diameter, cruciately or decussately divided.

Type from St Francis I., Isles of St Francis, S. Aust., 55 m deep (Shepherd, 9.i.1971); holotype in AD, A38087.

Selected specimens: Blanche Harbor, upper Spencer Gulf, S. Aust., 16 m deep (Reimers, 23.ix.1986; AD, A57261). Tinderbox, Tas., 7–10 m deep (Kraft 9236 & Sanderson, 20.xii.1992; MELU).

Distribution map based
on current data relating to
specimens held in the
State Herbarium of SA

Distribution: Known from the type specimen, and from Blanche Harbor, S. Aust., and Tinderbox, Tasmania.

Taxonomic notes: P. francisianum is distinguished by the overlapping major pinnae and the frequent pairs of adaxial pinnules on the whorl-branchlets. Athanasiadis (1996, p. 73) suggests it may be a synonym of P. antarcticum (Kylin) Moe & Silva (1980, p. 12, figs 1–9). The two species are clearly closely related, but P. francisianum is maintained here until further studies are possible based on sexual material.


ATHANASIADIS, A. & KRAFT, G.T. (1994). Description of Pterothamnion squarrulosum (Harvey) comb. nov. from south-eastern Australia and southern New Zealand, with a taxonomic re-assessment of the genera Pterothamnion, Platythamnion & Glandothamnus (Ceramiaceae, Rhodophyta). Eur. J. Phycol. 29, 119–133.

ATHANASIADIS, A. (1996). Morphology and classification of the Ceramioideae (Rhodophyta) based on phylogenetic principles. Opera Botanica No. 128, pp. 1–216.

MOE, R.L. & SILVA, P.C. (1980). Morphological and taxonomic studies on Antarctic Ceramiaceae (Rhodophyceae). II. Pterothamnion antarcticum (Kylin) comb. nov. (Antithamnion antarcticum Kylin). Br. phycol. J. 15, 1–17.

WOLLASTON, E.M. (1978). Two new species of Platythamnion J. Agardh (Ceramiaceae, Rhodophyta) from eastern and southern Australia. Trans. R. Soc. S. Aust. 102, 1–8.

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

Author: H.B.S. Womersley & E.M. Wollaston

Publication: Womersley, H.B.S. (24 December, 1998)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIIC. Ceramiales – Ceramiaceae, Dasyaceae
©State Herbarium of South Australia, Government of South Australia

Illustration in Womersley Part IIIA, 1998: FIGS 610–Q, 62A, B.

Figure 62 image

Figure 62   enlarge

Fig. 62. A, B. Pterothamnion francisianurn (AD, A38087). A. Upper slightly flexuous branches. B. Branches with pinnae hearing tetrasporangia. C. Pterothamnion aciculare (AD, A46154). Upper branches with tetrasporangia. D. Pterothamnion flexile (AD, A59341). Upper branches.

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