Comprehensive DescriptionRead full entry
“10. Arntzia López-González,
Gili and Orejas, 2002
Primnoella.—Molander, 1929:63 [in part].—Bayer, 1966:179 [in part: discussion].
Arntzia López-González, Gili and Orejas, 2002:385.
Diagnosis. Colonies unbranched (flagelliform). Calyces arranged in whorls of up to 22, the calyces inclined upward or oriented perpendicular to axis and, within each whorl, united at their bases. Brood chamber associated with the fused basal ring in each whorl. Polyps fleshy, a thin layer of tissue covering the calyces and branch, partially obscuring the underlying sclerites; calyces slightly flattened, as in Primnoella. Well-developed operculum present, each opercular scale having one or more ridges on its inner surface. Eight marginal scales do not overlap the operculars, the adaxial marginals smaller than the rest. Polyps protected by eight rows of 8–11 thin, smooth, rectangular scales, the adaxial scales smaller and in shorter rows (Figure 6a), resulting in a bare strip on lower adaxial polyp wall. Coenenchymal scales in two layers: outer layer composed of smooth scales; inner layer composed of small irregularly shaped tuberculate spheroids.
DISCUSSION. Although originally placed in Primnoella, Bayer (1996b) excluded P. gracilis from that genus but did not suggest an alternative. López-González et al. (2002) eventually established a new genus for it. Although the calyces are slightly flattened, Arntzia differs from Primnoella primarily in having marginal scales that do not overlap or override the bases of the operculars. It also differs in having fused calycular bases, nonappressed calyces, and internally ridged opercular scales. Furthermore, it seems to be unique among the primnoids in having a thin layer of tissue covering its scales.
DISTRIBUTION. Weddell Sea, Scotia Arc, and Ross Sea, 64–604 m.
TYPE SPECIES. Primnoella gracilis Molander, 1929, by original designation. The holotype is deposited at the Stockholm Museum of Natural History (1140)."
(Bayer & Cairns, 2009)