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FAMILY SARCOMENIACEAE Womersley, fam. nov.

Phylum Rhodophyta

Thallus erect, much branched, branches terete or compressed, usually gelatinous and decaying rapidly. Apical cells prominent, protruding, axial cells with 4 pericentral cells cut off in alternating sequence with the first-formed transverse pericentral cells lying in a linear row. The slightly larger lateral pericentral cells each cut off 2 half-length flanking cells (only associated with reproduction in Malaconema) which produce rows of cells in some genera. Branching endogenous (except for monosiphonous filaments in Dotyella and Sarcotrichia). Trichoblasts absent, but some genera with simple, monosiphonous, rhodoplastic filaments from the pericentral or flanking cells, arising well below the apices, or endogenous from axial cells (in Cottoniella).

Reproduction: Gametophytes dioecious. Procarps borne on the adaxial transverse pericentral cells, with a 4-celled carpogonial branch and 2 sterile cells; carposporophytes with a basal fusion cell and much branched gonimoblast with clavate terminal carposporangia, replaced from lower cells*; cystocarps external to branches, ovoid to urceolate, pericarp arising post-fertilization, ostiolate, with numerous erect filaments developed from adjacent pericentral cells, each cell cutting off 2–3 outer pericentral cells, corticated or not. Spermatangia borne in sori on the surface of shorter, compressed, lateral blades.

Tetrasporangia in stichidia, cut off from lateral pericentral cells, in 2 longitudinal, distichous, rows, in a single layer, with post-sporangial cover cells on both sides.

Type genus: Sarcomenia Sonder 1845: 56.

Taxonomic notes: The "Sarcomenia group" was studied in detail by Womersley & Shepley (1959) who concluded (p. 218) that the group "shows so many features which are characteristic of either the Delesseriaceae or the Rhodomelaceae that it must be recognised as forming an intermediate or linking group between the two families. It could be placed as a subfamily, the Sarcomenioideae, of either family or even recognised as an independent family." They considered it best placed as a subfamily of the Rhodomelaceae.

Following this account, Papenfuss (1961), Hommersand (1963) and Wynne (1969) supported retention of the Sarcomenia group within the Delesseriaceae, but (the first two) without knowledge of Sonderella (Womersley 1965), a distinctive member of the Rhodomelaceae.

While Womersley & Shepley had used the well-accepted (e.g. Papenfuss 1944, p. 200) feature of the order of pericentral cell formation in relating the Sarcomenia group to the Rhodomelaceae, the above 3 authors considered that because of the apparent delesseriaceous features of the group that this distinguishing feature could no longer be used. Other features they used (especially Hommersand 1963, p. 328) need to be reconsidered in fight of the study on Sonderella, which has 4 pericentral cells (5 in female and tetrasporangial segments), the lateral pericentral cells form two "flanking" cells each producing a row of cells, trichoblasts are absent and procarps and spermatangia occur on the blade surface, the procarps from the central of 3 pericentral cells on the adaxial side. The origin of tetrasporangia before the cover cells in the Sarcomenia group, as in the Delesseriaceae, differs from that in Sonderella which agrees with the reverse situation in the Rhodomelaceae.

In their catalogue of Indian Ocean algae, Silva et al. (1996) placed most of the sarcomenioid algae in the Delesseriaceae, but included Malaconema (p. 526) in the Rhodomelaceae. Discovery of a cystocarpic plant of Malaconema (see below) supports its position within the Sarcomeniaceae.

The relationships of the Sarcomenia group have been clarified by molecular studies by Professor Gary W. Saunders, of the University of New Brunswick, Canada, and colleagues* who have found that, based on sequencing data from Platysiphonia victoriae, the group allies somewhat weakly to the Rhodomelaceae and is far more likely to belong there than to the Delesseriaceae. Lin, Fredericq & Hommersand (2001) using sequencing data have found (their Fig. 1) that Sarcomenia delesserioides is closest to the Rhodomelaceae, but in their Figs 2 and 3 is closer to tribes of the Delesseriaceae; clearly this is an untenable situation. They conclude (p. 893) that the position of Sarcomenia was ambiguous and its taxonomic position remains problematic.

It now seems preferable to regard the Sarcomenia group as a family with a suite of characters shared by both the Rhodomelaceae (R) and Delesseriaceae (D), but most closely related to the former. The distinctive features of the Sarcomeniaceae are:

1. Pericentral cells 4 (D, some R), cut off in alternating sequence (R).

2. Flanking cells from the lateral pericentral cells (D and Sonderelleae), in some genera producing lateral rows of cells.

3. Absence of trichoblasts (D, Sonderelleae, some R).

4. Reproductive cells (female and male) borne on surface cells (D, Sonderelleae, some Polyzonieae).

5. Pericarp ovoid, based on erect filaments (R), developed post-fertilization (D).

6. Tetrasporangia cut off before the cover cells (D), in two longitudinal rows (some D and R).


HOMMERSAND, M.H. (1963). The morphology and classification of some Ceramiaceae and Rhodomelaceae. Univ. Calif. Pubis. Bot. 35(2), 165–366.

PAPENFUSS, G.F. (1944). Structure and taxonomy of Taenioma, including a discussion on the phylogeny of the Ceramiales. Madrono 7(7), 193–214.

PAPENFUSS, G.F. (1961). The structure and reproduction of Caloglossa leprieurii. Phycologia 1: 8–31.

SILVA, P.C., BASSON, P.W. & MOE, R.L. (1996). Catalogue of the Benthic Marine Algae of the Indian Ocean. (Univ. California Press: Berkeley.)

SONDER, O.G. (1845). Nova Algarum genera et species, quas in itinere ad oras occidentales Novae Hollandiae, collegit L. Preiss, Ph.Dr. Bot. Zeit. 3, 49–57.

WOMERSLEY, H.B.S. & SHEPLEY, E.A. (1959). Studies on the Sarcomenia group of the Rhodophyta. Aust. J. Bot. 7, 168–223.

WOMERSLEY, H.B.S. (1965). The morphology and relationships of Sonderella (Rhodophyta, Rhodomelaceae). Aust. J. Bot. 13, 435–450.

WYNNE, M.J. (1969). Platysiphonia decumbens sp. nov., a new member of the Sarcomenia group (Rhodophyta) from Washington. J. Phycol. 5, 190–202.

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

Publication: Womersley, H.B.S. (24 February, 2003)
The Marine Benthic Flora of Southern Australia
Rhodophyta. Part IIID. Ceramiales – Delesseriaceae, Sarcomeniaceae, Rhodomelaceae
Reproduced with permission from The Marine Benthic Flora of Southern Australia Part IIID 2003, by H.B.S. Womersley. Australian Biological Resources Study, Canberra. Copyright Commonwealth of Australia.


1. Thallus without flanking cells from the lateral pericentral cells of vegetative (indeterminate) branches, but these present in stichidia and where carpogonial branches develop


1. Thallus with flanking cells from the lateral pericentral cells


2. Free monosiphonous filaments present


2. Free monosiphonous filaments absent


3. Monosiphonous filaments formed endogenously from the central cells anterior to the adaxial transverse pericentral cell


3. Monosiphonous filaments formed exogenously from the anterior flanking cells of each segment and in S. tenera from the transverse pericentral cells


4. Flanking cells not dividing further in the vegetative thallus


4. Flanking cells dividing further, the anterior one producing 2 chains of cells, the posterior one a single chain of cells, which remain laterally adherent giving a strongly compressed thallus


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