A new genus and species of the family Isididae (Coelenterata: Octocorallia) from a CMAR Biodiversity study, and a discussion on the subfamilial placement of some nominal isidid genera

We describe a new abyssal genus and species of bamboo coral (family Isididae) with some markedly unusual characteristics, collected from a depth of just over 2000 m off southern Tasmania. Jasonisis thresheri n. gen., n. sp. possesses a fleshy tegument that contains nematocysts, tubular axial internodes that are internally partitioned, scale-shaped sclerites that have a morphology not recorded before for octocorals, and polyps that lack thorny rods or double stars in the pharynx. Molecular data place Jasonisis n. gen. in the subfamily Keratoisidinae whose definition is altered to incorporate the unusual characters. We also report some comparative observations on the internal structure of the axial internodes of the isidid genera Keratoisis Wright, 1869, Lepidisis Verrill, 1883 and Isidella Gray, 1857, and we alter the definition of the subfamily Mopseinae to allow the inclusion of the genera Tenuisis, Echinisis sensu Bayer & Stefani 1987 and Sclerisis sensu Bayer & Stefani 1987.