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A critical assessment of the dendrochirotid subfamilies, sclerodactylinae and thyoninae, with the taxonomic management of the "supergenus" thyone (echinodermata : holothuroidea)

The key character separating the dendrochirotid families Sclerodactylidae (sensu
Pawson & Fell, 1965) and the Phyllophoridae (sensu Pawson & Fell, 1965), i.e. entire
or undivided radial processes to the calcareous ring in the former and sub-divided
processes in the latter, is unjustified since most sclerodactylid species also have subdivided
processes. It is here assumed that the basis of elevating the subfamily
Sclerodactylinae Panning to family level was established on a misinterpretation or
mistranslation of the original diagnosis of this subfamily or a lapsus calumni meaning
“plates” instead of “processes”. Panning (1949) categorically states that the processes in
the Sclerodactylinae are composed of 3–4 large pieces of calcite and only as an
exception they are unbroken. Since Pawson & Fell gave no other distinction between
the Sclerodactylidae and the Phyllophoridae, the former is here considered an invalid
taxon and its three current subfamilies (Sclerodactylinae, Sclerothyoninae Thandar and
Cladolabinae Heding & Panning) are re-assigned to the Phyllophoridae. This family
now includes six subfamilies: Cladolabinae, Phyllophorinae Östergren,
Sclerodactylinae, Sclerothyoninae, Semperiellinae Heding & Panning and Thyoninae
Panning. The diagnosis of the Sclerodactylinae, restricted by Thandar (1989), is now
modified to include also those forms whose radial and interradial plates may be slightly
sub-divided but still form a short tube. Of the eleven genera placed within this
subfamily subsequent to its erection, only ten of these remain. Neothyone Deichmann is
a preoccupied name for which Lisacucumis is here proposed as a replacement.
Thandar’s (1989) diagnosis of the Thyoninae is here accepted, however, the genus
Thorsonia Heding is transferred to the Sclerodactylinae. Of the 66 nominal species
which currently stand in the “supergenus” Thyone Jaeger, 10 are transferred to
Havelockia Pearson within the Sclerodactylinae, while one species is regarded as a
synonym of H. herdmani Pearson. In addition, six species are transferred to Stolus
Selenka within the Thyoninae. Finally, three species are transferred to Sclerothyoninae,
two within Sclerothyone Thandar and one within Temparena Thandar. Two species
show an uncertain affinity to Thyone and are temporally removed from the genus.
Furthermore, two species currently classified within Havelockia are transferred to
Thyone. The now remaining 46 species are separated into seven groups based on the
composition of their introvert deposits: tables only (8 spp.), rosettes only (5 spp.), tables
and rosettes (21 spp.), tables and plates/?reduced tables (2 spp.), rosettes and
plates/?reduced tables (3 spp.), plates only (2 spp.), or introvert deposits absent or
unknown (5 spp.). Regrettably, no other character could be used in conjunction with the
above to suggest at least sub-generic levels. Within the genus Havelockia, Cucumaria
redimita Sluiter indicates an affinity with Pentamera Ayres. It is here transferred to this
genus within the Thyoninae. Havelockia, now containing 17 species, is also revised.
Keys, diagnoses and figures are provided for all nominal species now included in
Thyone and Havelockia. / Thesis (M.Sc.)-University of KwaZulu-Natal, Westville, 2011.

Identiferoai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:ukzn/oai:http://researchspace.ukzn.ac.za:10413/9703
Date10 October 2013
CreatorsArumugam, Preyan.
ContributorsThandar, Ahmed Suleman.
Source SetsSouth African National ETD Portal
Languageen_ZA
Detected LanguageEnglish
TypeThesis

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