Keratoisididae Gray, 1870

Saucier, Esprit Heestand, France, Scott C. & Watling, Les, 2021, Toward a revision of the bamboo corals: Part 3, deconstructing the Family Isididae, Zootaxa 5047 (3), pp. 247-272 : 267-268

Family Keratoisididae Gray, 1870 , n. rank

Ceratoisidae Verrill 1883

Type genus: Keratoisis Wright (1869)

Diagnosis. Colonies typically with an articulated skeleton of hollow or solid calcium carbonate internodes interrupted by brown to dark brown proteinaceous and sclerite-free nodes. unbranched (“whip-like”) or branched with branches originating at the nodes, or from the internodes, either immediately distal to the nodes, or from midway along the internode. Coenenchyme usually thin but sometimes slightly thickened. Colonies may be covered in a fleshy tegument containing nematocysts. Polyps are contractile to varying degrees, but never within the coenenchyme, or only the tentacles contract over the polyp body oral area. Sclerites are only needles, spindles, rods, or scales that are arranged longitudinally, transversely, or obliquely along the polyp body and in the coenenchyme. One or a cluster of mesenterially arranged needle-like sclerites protrude between the bases of the tentacles in many species (in contrast to the intermesenterially arranged anthopomal sclerites of the Mopseidae ); other species may not possess needles but a mesenterial arrangement of rod-like sclerites may still be present. Pharyngeal sclerites usually present; include tuberculated or spiny rodlets, and double stars.

Included genera: Acanella Gray (1870) , Bathygorgia Wright (1885) , Cladarisis Watling 2015 , Eknomisis Watling & France (2011) , Isidella Gray (1857) , Jasonisis Alderslade & McFadden (2012) , Keratoisis Wright (1869) , Lepidisis Verrill (1883) , Orstomisis Bayer (1990) .

Remarks. The Keratoisididae is the most morphologically and genetically diverse of the families resulting from the revision of the Isididae . That diversity is manifested in colonies that range in size from a few centimeters to several meters; from tall spindly whips to large bushes; from polyps that contract to small mounds on the branches to tall polyps where only the tentacles contract over the mouth; from polyps with large numbers of needles, rods, or scales to polyps with barely any sclerites but a thick outer integument; or from polyps covered with a nematocyst impregnated integument to polyps where the outer layer of cells is barely discernable. Some of the variation seems to be derived secondarily. For example, small, bramble-like colonies that we have observed on both Atlantic and Pacific seamounts seem to possess an unarticulated axis that, based on the placement of those species in a more complete phylogenetic analysis of Keratoisididae , may represent a loss of that feature ( Heestand Saucier, 2016). All of these variations characterize a large number of clades within the family that will be dealt with in a companion paper.

Brugler and France (2008) identified a novel (at the time) mitochondrial gene arrangement for keratoisidids, and this, along with our preliminary molecular phylogeny results, drew our attention to the idea that the family Isididae was polyphyletic, as suggested more than a century ago by Kükenthal (1919). Subsequent analyses showed the “S1 clade” of Keratoisididae (that includes Cladarisis Watling 2015 ) to possess the presumed ancestral octocoral mitochondrial gene order ( Pante et al. 2013), and, more recently, Hogan et al. (2019) have reported the interesting finding that species of Pennatulacea in the genus Anthoptilum have the same “keratoisidin” mitochondrial genome arrangement found by Brugler and France (2008). Thus, a specific mitochondrial gene arrangement cannot be used as a synapomorphy of this newly erected family.