Pachyarthron Manza, 1937

Holotype species: Pachyarthron cretaceum (Postels & Ruprecht) Manza

Currently accepted name for the type species: Corallina officinalis Linnaeus

Original publication and holotype designation: Manza, A.V. (1937). The genera of the articulated corallines. Proceedings of the National Academy of Science of the United States of America 23: 44-48.

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Description: Plants consisting of a crustose base and upright axes composed of distinct, alternating calcified segments (intergenicula) and uncalcified segments (genicula); branching mainly irregular but with occasional dichotomies or trichotomies. Thallus construction monomerous, consisting of a single system of branched, pseudoparenchymatously united filaments. Intergenicula more or less cylindrical or occasionally slightly compressed, composed of a core (medullary) region in which thin-walled elongate cells of adjacent filaments become more or less aligned to form a number of tiers of arching cells, and a peripheral (cortical) region where shorter-celled distal portions of core filaments or their derivatives bend outward and terminate at the thallus surface in small epithallial cells; vegetative branch apices composed only of core filaments that terminate in elongate meristematic initials. Genicula derived from transformed core filament cells, composed of a single tier of elongate, thick-walled cells that connect adjacent intergenicula. Cells of adjacent intergenicular filaments linked by cell fusions; genicula devoid of cell fusions. Life history triphasic with separate, isomorphic male, female/carposporangial and tetrasporangial/bisporangial plants. Gametangia and sporangia developing within uniporate conceptacles; female/carposporangial conceptacles and tetrasporangial/bisporangial conceptacles always lateral [formed in peripheral (cortical) regions of intergenicula], protruding from the intergenicular thallus surface; male conceptacles both lateral and axial (formed centrally at the distal ends of intergenicula either at points of branch dichotomies or at tips of branches); conceptacles clumped or scattered over intergenicula and in male plants also occurring at intergenicular apices. Marginal conceptacles (formed at the distal margins or on distal shoulders of intergenicula) absent. Carpogonial filaments arising from the floor of female conceptacle chambers; carposporangia formed after fertilisation, terminating several-celled carposporangial filaments that arise from the upper surface and margins of a fusion cell. Spermatangia terminating short unbranched filaments anchored to the floor and walls of male conceptacle chambers. Tetrasporangia/bisporangia arising from the conceptacle chamber floor, with zonately arranged spores.

Information kindly contributed by From Woelkerling et al. 2008: 267 but may now be outdated.

Taxonomic status: This name is currently regarded as a synonym of Corallina.

Most recent taxonomic treatment adopted: Hind, K.R., Gabrielson, P.W., Lindstrom, S.C. & Martone, P.T. (2014). Misleading morphologies and the importance of sequencing type specimens for resolving coralline taxonomy (Corallinales, Rhodophyta): Pachyarthron cretaceum is Corallina officinalis (Note). Journal of Phycology 50(4): 760-764.

Comments: ETYMOLOGY: Pachyarthron, from the Greek, meaning thick joint. Manza (1937) did not explain the name derivation.

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Some of the descriptions included in AlgaeBase were originally from the unpublished Encyclopedia of Algal Genera, organised in the 1990s by Dr Bruce Parker on behalf of the Phycological Society of America (PSA) and intended to be published in CD format. These AlgaeBase descriptions are now being continually updated, and each current contributor is identified above. The PSA and AlgaeBase warmly acknowledge the generosity of all past and present contributors and particularly the work of Dr Parker.

Descriptions of chrysophyte genera were subsequently published in J. Kristiansen & H.R. Preisig (eds.). 2001. Encyclopedia of Chrysophyte Genera. Bibliotheca Phycologica 110: 1-260.

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Paul Gabrielson in Guiry, M.D. & Guiry, G.M. 17 August 2014. AlgaeBase. World-wide electronic publication, National University of Ireland, Galway.; searched on 25 September 2022

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