Genus Zibrovermilia gen. nov.

Type-species: Zibrovermilia zibrowii gen. et sp. nov.

Diagnosis. Tube white opaque, quadrangular in cross-section; with 4 denticulate keels, distal parts circular in cross-section, without ring-like peristomes. Operculum an inverse conical ampulla, with chitinous endplate; borne on 2nd normal pinnulated radiole. Pseudoperculum absent. Radioles arranged pectinately, inter-radiolar membrane absent. Radiolar eyes not observed. Stylodes absent. Mouth palps not observed. Seven thoracic chaetigerous chaetigers, including six uncinigerous. Collar trilobed, tonguelets between ventral and lateral collar parts absent. Thoracic membranes short, ending at 2nd–3rd thoracic chaetiger. Collar chaetae limbate, of two sizes. Apomatus chaetae present. Thoracic uncini rasp-shaped with up to 15 teeth in profile and 4–5 teeth in frontal view above blunt peg. Triangular depression absent. Abdominal chaetae flat narrow geniculate, blade with a more or less crenulated edge (rounded teeth). Abdominal uncini rasp-shaped, anterior peg blunt. Achaetous anterior abdominal zone absent. Long posterior capillary chaetae present. Posterior glandular pad absent.

Remarks. The new species is attributed to a new genus mainly because of its very peculiar quadrangular tubes with serrated edges, its pinnulated peduncle and its rasp-shaped thoracic uncini. Zibrovermilia gen. nov. is most similar to Bathyvermilia Zibrowius, 1973 and Vermiliopsis de Saint-Joseph, 1894 in the chaetation pattern (except for rasp-shaped thoracic and abdominal uncini in Zibrovermilia gen. nov.), length of thoracic membranes, and opercular morphology (Table 3). According to Zibrowius (1973), the main differences between Bathyvermilia and Vermiliopsis are the insertion of smooth opercular peduncle as second radiole in the former and as the first in the latter. However, ten Hove & Kupriyanova (2009) argue that the peduncle is ontogenetically formed from second dorsal radiole on one side, but in adults it often located at base of radiolar crown covering 3–6 normal radioles, which would undermine Zibrowius’rather absolute “difference”.

In Zibrovermilia gen. nov. the second normal (pinnulated) radiole bears the operculum with a chitinous endplate lacking any calcification. Ten Hove (1984, 1989) distinguishes between indirect (juveniles develop an operculum on a pinnulated radiole that later loses its pinnules and becomes smooth) and direct (peduncle and operculum develop directly, without a pinnule-bearing stage) opercular ontogeny. It is unclear what kind of opercular ontogeny is typical for the genera of the Vermiliopsis -group, but in the case of indirect development the “diagnostic” pinnulated peduncle of Zibrovermilia might be neotenic and thus not very reliable.

The assignment of the newly described species, Z. zibrowii gen. et sp. nov., to a new monospecific genus is a result of a unique combination of its characters. Although the tube of Z. zibrowii gen. et sp. nov. is quadrangular in cross-section and the peduncle is pinnulated like that in Spirodiscus and Bathyditrupa, the similarities end here. The operculum-bearing radiole in Z. zibrowii gen. et sp. nov. is similar to other radioles, not modified into a thick peduncle as seen in Spirodiscus and Bathyditrupa and the tubes are large and thick-walled, with denticles on the edges. The new species is similar to Bathyvermilia gregrousei sp. nov. in having 7 thoracic segments, thoracic Apomatus chaetae, and very typical Bathyvermilia or Vermiliopsis - type abdominal chaetae. The blunt slightly indented pegs of uncini in Z. zibrowii gen. et sp. nov. are reminiscent of those observed in Vermiliopsis infundibulum (Philippi, 1844) (compare fig. 49C in ten Hove & Kupriyanova 2009). However, thoracic uncini of the new genus are rasp-shaped, not saw-shaped as in Vermiliopsis and Bathyvermila. Pinnulated peduncles are not found either in Bathyvermilia or in Vermiliopsis . Table 3 summarises characters found in the Vermiliopsis -group genera. When molecular data on phylogenetic position of the species become available, the taxonomic position of Zibrovermilia gen. nov. may have to be reconsidered.

Etymology. The genus is named after Dr Helmut Zibrowius who made important contributions to serpulid taxonomy and provided most of material for this study; - vermilia stresses the similarity with other genera (Table 3), with this stem.