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Genus ACROTHAMNIOPSIS Athanasiadis & Kraft in Athanasiadis 1996: 92

Phylum Rhodophyta – Order Ceramiales – Family Ceramiaceae – Tribe Heterothamnieae

Thallus largely prostrate with more or less erect laterals, basically complanately branched, each axial cell with 2 pinnate major whorl-branchlets and (1–) 2 minor whorl-branchlets on both dorsal and ventral surfaces. Attachment by a series of rhizoids with clumped haptera, from successive cells of minor whorl-branchlets; epiphytic on crustose coralline algae. Structure. Apical cells enlarging relatively rapidly to mature axial cells, with lateral branches developed alternately usually 2 axial cells apart. Major whorl-branchlets over 200 µm long, pinnately branched with pinnules also becoming pinnate; minor whorl-branchlets shorter and less developed; rachides with a shorter basal cell; gland cells frequent, on lower pinnule cells, touching the bearing cell and abutting the next cell. Cells uninucleate.

Reproduction: Gametophytes dioecious. Carpogonial branches borne on the basal cell of major whorl-branchlets; carposporophytes terminal, with 1–3 gonimolobes, partly surrounded by whorl-branchlets from below. Spermatangia on branched filaments on pinnule cells.

Tetrasporangia occur on rachis and lower pinnule cells, sessile or pedicellate, ovoid, tetrahedrally or subdecussately divided.

Type species: A. eliseae Athanasiadis & Kraft in Athanasiadis 1996: 92.

Taxonomic notes: Acrothamniopsis is a distinctive monospecific genus, characterised by its habit, arrangement of major and minor whorl-branchlets, and the unusual arrangement of rhizoids, emitted from a series of cells and with clumped hapteroid ends but the shafts of the rhizoids free from each other.


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

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
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