Crispatotrochus gregarius, Cairns, 2004

Cairns, S. D., 2004, The Azooxanthellate Scleractinia (Coelenterata: Anthozoa) of Australia, Records of the Australian Museum 56, pp. 259-329 : 279

Crispatotrochus gregarius n.sp.

Figs. 3H–J

Records/Types. About 30 coralla (syntypes), all originally part of one fused mass, now in two parts ( QMB GL10161 ). Type Locality: “Southern Intruder” 15, 23°21'S 153°56'E (continental slope off Gladstone , Queensland), 460 m.

Description. Syntypes consist of a pseudocolony formed of 2 large coralla that are completely encrusted with about 30 smaller coralla, 6 of which are large and intact, the others broken at their bases, damaged, or juveniles. Initially, the corallum was thought to be a true colony, but closer examination showed that each corallum had an independent origin, not being a direct outgrowth of a parent corallite as in asexual reproduction. In fact, many of the larger basal coralla were long dead, whereas the smaller and some of the larger distal coralla still had tissue. Individual coralla ceratoid, elongate, and not flared distally, the largest intact specimen 19.3× 15.8 mm in CD, 45 mm in height, and 6.7 mm in PD. Calice elliptical, the GCD:LCD ranging from 1.13 to 1.22. Pedicel robust (PD:GCD = 0.34–0.46), spreading basally to encrust the substrate, which in this case consisting of conspecific coralla. Upper half of theca bears low costal ridges corresponding to the 40 primary to tertiary septa, but these ridges diminish toward the base, being replaced by a low, transverse sculpturing. Corallum white.

Septa decamerally arranged in 4 systems, the complete number being 80 septa, but none of the coralla have that number. The largest 2 coralla of GCD 19.3 mm have an extra pair of fifth cycle septa (i.e., 84 septa), whereas a corallum of 17.0 mm GCD has 82 septa, and one of 17.4 mm lacks a pair of S4, resulting in 78 septa. The 10 primary septa are only slightly exsert (about 1.5 mm), their axial edges highly sinuous, standing directly adjacent to the columella. The 10 secondary septa are less exsert (0.6 mm), have equally sinuous axial edges, and are almost as wide as the primaries, being about 95% of their width. The 20 tertiary septa and all those of higher cycle have straight axial edges, and are about 75% the width of a primary, the quaternary septa being only about 15% the width of a primary. Fossa moderately deep, containing an elongate columella consisting of 10–15 loosely swirled lamellar plates that are interconnected among themselves, almost bridging the gap between the columella known for Crispatotrochus and Labyrinthocyathus .

Remarks. Two of the 11 Recent species of Crispatotrochus have decameral septal symmetry, Cr. woodsi ( Wells, 1964) and Cr. squiresi ( Cairns, 1979) , as well as two unnamed species referred to as Cyathoceras sp. sensu Cairns, 1979 and Cyathoceras sp. A sensu Cairns, 1982. Crispatotrochus gregarius differs from these four taxa in having larger coralla with more septa (the other species having only 40 septa), having transverse thecal sculpture, and in having an interconnected columella (the elements of other species being discrete).

Etymology. gregarius, Latin for “pertaining to a flock”, or “gathering objects together”, an allusion to the quasicolonial nature of the coralla of the type specimens.

Distribution. Known only from the type locality off Gladstone, Queensland, 460 m.