Chondriovelum Hayward and Thorpe 1988

Genus Chondriovelum Hayward and Thorpe, 1988

(Figure 5)

Type species

Labioporella adeliense Livingstone, 1928, by original designation. Recent, Antarctic coastal waters (see Hayward 1995).

Diagnosis

Colony encrusting or developing erect, bifoliate branches. Autozooids rounded hexagonal; zooidal boundaries raised with a medial groove. Cryptocyst extensive, granular. Gymnocyst lacking. Opesia terminal, occupying about one-third of frontal surface; semielliptical, wider than long, proximal edge convex, distal edge almost straight, lacking opesiular indentations or lateral constrictions (Figure 5 (a)). Ovicells unknown. Avicularia vicarious, asymmetrical (Figure 5 (b)), the same size as an autozooid; granular surface perforated by several small openings, usually a proximal median irregular opening (?opesia) followed by a pair of slit-like openings and a small distal opening; condyles lacking; rostrum acutely triangular, floor pustulose.

Remarks

Hayward and Thorpe (1988) compared Chondriovelum with Smittipora (see below), noting that their new genus had a more extensive cryptocyst and a long, curved distal groove in the avicularium to accommodate the rachis of the mandible. Apart from the type species, two other species have been assigned to Chondriovelum: Smittipora angustiloba Moyano, 1974, from the Magellanic region of Chile; and Chondriovelum fossilis Gordon and Taylor, 1999, a fossil from the Paleocene Red Bluff Tuff of the Chatham Islands, New Zealand. The opesia is proportionally larger in C. angustiloba than it is in C. adeliense and there are two rather than four openings in the cryptocyst of the avicularium. The Paleocene species C. fossilis also has two openings in the cryptocyst, the distal one large and identifiable as the opesia. Unlike the two Recent species, colonies of C. fossilis are erect with cylindrical branches (‘vincularian’).

Gontar (2012, p. 207) claimed that Chondriovelum adeliense has an aragonite skeleton rather than the calcite skeleton that is usual for onychocellids and also for Antarctic bryozoans in general. However, analysis of a specimen from the NHMUK collections failed to find any aragonite and revealed a calcite skeleton instead (Taylor et al. 2009).

Range

Paleocene to Recent.