Stephanocyathus (Stephanocyathus) isabellae Reyes & Santodomingo & Cairns 2009, new species

Stephanocyathus (Stephanocyathus) isabellae , new species

Figs. 3O–R

Description: The corallum is free, with a slightly rounded base without trace of previous attachment scar; however, regeneration scars are always present; polychaete tubes have been incorporated on the base of some specimens. The C1-C2 septocostae are thin, not well defined, but always reach the base center; C3 is evident, only near the calicular edge, and the C4-C5 are a series of minute spurs near the calicular margin. Costae are formed by the lateral fusion of the high and slender granules bases; dorsal costae and coastal granules bear a shallow and thin furrow along its length as fracture lines. Intercostal spaces are wide, showing along its central section relatively deep holes alternating with tall spine shape granules, some of the latter are fused near the calicular margin constituting a short secondary ridged costae. The calicular edge is slightly lanceolated, projecting at the S1-S2 ends. The septal arrangement is not well defined; but corallites always show up to 103 septa in five cycles (S1≥S2>S3>S4≥S5), the fifth never complete. S1 are the only independent septa; S3-S4 join to their superior septa through several slender synapticulae or by a thin plate. S5 are conspicuous near the calicular edge, but up to 1/3–1/2 of the columella distance each S5 is reduced to a slender spines row that reach the columella. Paliform lobes (P1-P2) are small and their septal notches are shallow and wide; S3 to S5 no have paliform lobes. Upper septal and palar edges are smooth near the calicular margin, but from half of the columella distance they become serrated and bear numerous transversely oriented bent granules. The S2- S3 axial sides present granules which are fused to the columella elements. Lateral septal faces present low and rounded scattered granules. All septa are exsert (S1≥S2>S3≥S4>>S5). Columella is small, fascicular in larger corallites, composed of elements derived from the axial edge of septa; sometimes absent in smaller corallites. Fossa is shallow. Corallites are white or creamy.

Discussion: S. isabellae belongs to the genus Stephanocyathus because of the presence of paliform lobes instead of pali, the septal notches are shallow and wide, and its columella is composed by elements derived from the septal axial edges. S. isabellae differs from other Atlantic Stephanocyathus, but some specimens resemble juvenile forms of S. diadema, due to their lanceolated calicular edges (Cairns 1979). The septal edge granulation, and its rudimentary S5 are similar to those described for Stephanocyathus moseleyanus (Sclater, 1886) sensu Zibrowius (1980: pl. 49 fig. F). On the other hand, the small paliform lobes and the septal edge ornamentation are similar to Stephanocyathus crassus (Jourdan, 1895) sensu Zibrowius (1980: pl. 50, fig. G), but neither of the mentioned species had been previous recorded in the tropical western Atlantic. S. isabellae is distinguishable from the other species of the genus by its basal regeneration scars, the observed thin furrows at the dorsal section of the costae, and by its particular intercostal spaces as longitudinal fracture lines, all perhaps due to its characteristic parricidal budding as the common reproductive mode in the species.

Distribution: Tropical western Atlantic, off Louisiana (Gulf of Mexico); Caribbean, off the southwestern Walton Bank (Jamaica). In Colombia, this species was found off Cabo de La Vela (La Guajira) to off San Bernardo Islands; ranging from 408 to 732 m depth.

Etymology: This new species is named after the youngest daughter of J. Reyes, Isabella Reyes.

Material: Holotype, INV CNI395, 1 specimen, 24.7 mm GCD, E54, Colombia (off Bocas de Ceniza). Paratypes: INV CNI694, 2 specimens, 25.5 and 24.4 mm GCD, respectively, E150, Colombia (off San Bernardo Islands); USNM 100539, 1 specimen, 12.7 mm GCD, P - 1256, Jamaica (SE of Walton Bank); USNM 100538, 1 specimen, 20.9 mm GCD, CI-83 R / V Columbus Iselin, Straits of Florida; USNM 100537, 1 specimen, O-3252, Gulf of Mexico (off Louisiana). Additional records: USNM 100540, 1 fragment, P-776, Colombia (La Guajira, off Aramtka Point); INV CNI691, 1 specimen and 3 fragments, E93, Colombia (La Guajira, off Cabo de la Vela); INV CNI692, 3 fragments, E115, Colombia (La Guajira, off Buritaca); INV CNI693, 1 specimen, E92, Colombia (La Guajira, off Cabo de la Vela).