REVISIONARY SYSTEMATICS IN THE GORGONIAN FAMILY ISIDIDAE, WITH DESCRIPTIONS OF NUMEROUS NEW TAXA (COELENTERATA: OCTOCORALLIA)

WA Museum Records and Supplements | Updated 9 years ago

Abstract - The work is a taxonomic treatment of a number of closely related groups of gorgonians within the family Isididae (Octocorallia: Coelenterata). The revisionary aspects of the study are centred around the genus Mopsea which is shown to be grossly paraphyletic. Heretofore including 17 nominal species, it is proposed that only the type species Mopsea encrinula is valid; a second, new species is added. Of the other recognised species, Mopsea dichotoma (Linne) is an unidentifiable melithaeid, and the remainder are divided amongst 1 existing and 7 new genera. These re-assignments are primarily on the basis of polyp structure, colonial branching pattern, and axial architecture, which are correlated with sclerite form and arrangement. Various states of these characters are used to define the relatedness of other genera. Taxonomic confusion is most likely to arise amongst both unbranched forms and branched forms which are predominantly planar, so the species of all known closely related genera with these morphologies are revised. The latter comprises the recognised and valid genera Acanthoisis, Peltastisis, Circinisis, Minuisis and the neglected Notisis. Although Minuisis has a generally bushy habitus, it is included because its growth form is modified to pinnate, planar branching by a commensal scale worm. It is shown that Primnoisis, Chathamisis, and Echinisis which have a bushy growth form can be distinguished as a group on this character, and individually using polyp structure; and these taxa are only considered at the generic level. Descriptions are extensively illustrated with scanning electron micrographs and all preparation techniques are detailed.

The revision of known species is based on type material borrowed from numerous Australian and international institutions. As far as can be ascertained, virtually all of the specimens mentioned in the literature that were considered to be relative to the study have been examined, together with a large suites of additional and previously undescribed material. Numerous new taxa are proposed based on these specimens. In total, 23 established species are validated, 15 as new combinations, and 30 new species are proposed along with 16 new genera. These taxa are assigned to the subfamilies Mopseinae and Circinisidinae, while Peltastisidinae is considered to be untenable. Keys to the genera of the former 2 subfamilies are given.

Lectotypes are designated for the following species Mopsea flabellum Thomson and Mackinnon, M. elegans Thomson and Mackinnon, and M. simplex Tixier-Durivault, and all 3 are assigned to new genera.

The history of all the relevant taxa is given inclusive of all reassignments made in the taxonomic portion of the ~ext. Some new terms are introduced in the section on taxonomic characters and terminology, which contains a particular point of focus on polyp structure. The misuse of the terms anthocodia and anthostele is discussed, and the neglected term anthopoma is reintroduced for the 'opercular' region of the polyp. Each of the defined character states pertaining to polyp structure, axial architecture, and the pattern of ramification, are shown, with rare exceptions, to be consistent within the proposed generic groups.

Distribution maps are given for all species, genera, and subfamilies. A preliminary model is proposed of the broad evolutionary history of the subfamilies in an attempt to explain the disparate distribution ranges of the bushy and non-bushy forms which may have had separate subsequent lineages from a common ancestor.