Euclavella Kott 1990

Type species: Colella claviformis Herdman, 1899

Zooids are embedded completely in common test and both smooth-rimmed apertures, each on a short muscular siphon open separately to the exterior. Embryos appear to be fertilised and are incubated in the distal expanded part of the oviduct at the top of the oesophageal neck. Although replication has not yet been described for this monotypic genus it may involve the long posterior abdominal stolon containing an epicardial tube as in Pycnoclavella (see Trason 1963), rather than the mesodermal tissue of terminal ampullae of the branched stolonic vessels as it does in the Clavelinidae. This monotypic genus is assigned to the Pycnoclavellidae on the basis of its (possibly vegetative) stolon, wide branchial sac with wide interstigmatal membranes and deeply invaginated tubular larval adhesive organs. The developmental sequence of embryos at the top of the oesophageal neck where the distal part of the oviduct is expanded to act as a brood pouch also occurs in some Pycnoclavellidae (e.g. the detorta group: see Kott 2005), in some Clavelinidae (see Kott 1990) and in the South Australian Sigillina fantasiana (Kott, 1957).