Antithamnion hubbsii, copyright Ignacio Bárbara.

Belongs within: Ceramiales.

Antithamnion is a genus of delicate red algae with an ecorticate thallus.

Characters (from Womersley 1998): Thallus usually 2–20 mm high, delicate, with prostrate and occasionally erect indeterminate axes, completely ecorticate, bearing determinate whorl-branchlets (often as pinnae) in opposite pairs, each with a small unbranched basal cell and other rachis cells bearing opposite, alternate or secund pinnules; gland-cells sessile on short 2–4-celled branchlets on the pinnules; attachment of prostrate axes by rhizoids with haptera; usually epiphytic. Cells uninucleate. Gametophytes usually dioecious. Procarps on the basal cells of whorl-branchlets near apices of indeterminate branches, with series of (4–)8–20 developed successively; the basal cell acts as the supporting cell and bears a 4-celled carpogonial branch, and only a single carposporophyte matures per branch. Post-fertilization the auxiliary cell is cut off the supporting cell and divides to form a lower foot cell and upper gonimoblast cell which forms one or a few rounded groups of carposporangia; no involucral branchlets occur. Spermatangia occur in branched clusters on cells of the pinnules. Tetrasporangia occur on cells of the pinnules, usually sessile, cruciately divided.

<==Antithamnion Nägeli 1847HL09
    |--A. adnatum Agardh 1892L27
    |--A. antillanum Børgesen 1917HL09
    |--A. applicitum (Hooker & Harvey) Agardh 1892L27
    |--A. armatumHK90
    |--A. cruciatum [=Callithamnion cruciatum]G64
    |--A. defectum Kylin 1925S57
    |--A. densiusculum Gardner 1927S57
    |--A. densumKBC03
    |--A. divergensHK90
    |--A. flaccidum (Hooker & Harvey) De Toni 1903 [=Callithamnion flaccidum]L27
    |--A. floccosum (Müller) Kleen 1874S57
    |--A. glanduliferum Kylin 1925S57
    |--A. hubbsiiN10
    |--A. interruptumG64
    |--A. kylinii Gardner 1927S57
    |--A. mucronatum (Agardh) Naeg. 1861L27
    |--A. nigricans Gardner 1927S57
    |--A. occidentale Kylin 1925S57
    |--A. pacificum (Harvey) Kylin 1925 (see below for synonymy)S57
    |--A. plumula (Ellis) Thuret 1863L27
    |    |--A. p. var. plumulaL27
    |    `--A. p. var. investiens Agardh 1876L27
    |--A. ptilota (Hooker & Harvey) Harvey 1893L27
    |--A. sparsumSK02
    |--A. subulatum (Harvey) Agardh 1892 [=Callithamnion subulatum]S57
    `--A. uncinatum Gardner 1927S57

Antithamnion pacificum (Harvey) Kylin 1925 [=A. floccosum var. pacificum; Callithamnion floccosum var. pacificum non C. pikeanum var. pacificum]S57

*Type species of generic name indicated


[G64] Gray, J. E. 1864. Handbook of British Water-weeds or Algae. R. Hardwicke: London.

[HK90] Huisman, J. M., G. A. Kendrick, D. I. Walker & A. Couté. 1990. The marine algae of Shark Bay, Western Australia. In: Berry, P. F., S. D. Bradshaw & B. R. Wilson (eds) Research in Shark Bay: Report of the France-Australe Bicentenary Expedition Committee pp. 89–100. Western Australian Museum.

[HL09] Huisman, J. M., F. Leliaert, H. Veerbruggen & R. A. Townsend. 2009. Marine benthic plants of Western Australia’s shelf-edge atolls. Records of the Western Australian Museum Supplement 77: 50–87.

[KBC03] Kashin, I. A., E. V. Bagaveeva & S. F. Chaplygina. 2003. Fouling communities of hydrotechnical constructions in Nakhodka Bay (Sea of Japan). Russian Journal of Marine Biology 29: 267–283.

[L27] Laing, R. M. 1927. A reference list of New Zealand marine algae. Transactions and Proceedings of the New Zealand Institute 57: 126–185.

[N10] Norris, J. N. 2010. Marine algae of the northern Gulf of California: Chlorophyta and Phaeophyceae. Smithsonian Contributions to Botany 94: 1–276.

[SK02] Saunders, G. W., & G. T. Kraft. 2002. Two new Australian species of Predaea (Nemastomataceae, Rhodophyta) with taxonomic recommendations for an expanded Nemastomatales and expanded Halymeniales. Journal of Phycology 38: 1245–1260.

[S57] Scagel, R. F. 1957. An annotated list of the marine algae of British Columbia and northern Washington (including keys to genera). National Museum of Canada Bulletin 150: 1–289.

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