Laonome Malmgren, 1866

Bick, Andreas, Bastrop, Ralf, Kotta, Jonne, Meyer, Maria & Syomin, Vitaly, 2018, Description of a new species of Sabellidae (Polychaeta, Annelida) from fresh and brackish waters in Europe, with some remarks on the branchial crown of Laonome, Zootaxa 4483 (2), pp. 349-364 : 352

Laonome Malmgren, 1866

Type species: Laonome kroyeri Malmgren, 1866

Diagnosis (emended). Six to twelve thoracic and numerous abdominal chaetigers. More than three pairs of radioles; radiolar skeleton composed of two interdigitated cell rows. Dorsal lips and ventral lips fused. Parallel lamella present. Radiolar appendages, dorsal pinnular appendages and ventral radiolar appendages present or absent. Palmate membrane present or absent. Anterior peristomial ring with ventral lobe or of equal height all around; posterior peristomial ring collar present. Ciliary patch formed by the parallel lamella extending the entire mid-ventral length of the collar. Transverse ridge at the junction of the posterior peristomial ring and first chaetiger. Thorax with superior narrowly hooded and inferior paleate notochaetae, and neuropodial avicular uncini with main fang, apical with several rows of small teeth, without handle; companion chaetae present or absent. Abdominal chaetigers with broadly-hooded neurochaetae, and notopodia with avicular uncini with main fang, apical with several rows of small teeth, without handle. Pygidium without eyes and cirri.

Remarks. The above diagnosis is emended with regard to the dorsal pinnular appendages, ventral radiolar appendages, parallel lamella, and number of thoracic chaetigers. Laonome xeprovala sp. nov. possesses dorsal pinnular and ventral radiolar appendages. Their absence was stressed in former diagnoses (e.g. Capa 2007, Capa et al. 2014), although small dorsal pinnular appendages and structures similar to ventral radiolar appendages were previously observed in some specimens of L. calida ( Capa 2007) . The presence of parallel lamella for Laonome has never been recorded before but was found not only in the type species L. kroyeri but also in L. triangularis and L. xeprovala sp. nov. The presence of an extended ciliary patch on the posterior peristomial ring and a narrow, white, transverse ridge between the posterior peristomial ring and chaetiger 1 were already assumed to be an apomorphic character of Laonome by Nogueira et al. (2010). The number of thoracic chaetigers seems to be highly variable not only between but also within the species of this genus. For example, Evenkamp (1931) found 8 to 12 thoracic chaetigers in L. kroyeri from the Baltic Sea, and Capa (2007) found 6 to 8 thoracic chaetigers in L. calida . The number of these chaetigers is obviously not size-dependent. The presence or absence of different structures of the radiolar crown, e.g., the radiolar appendages and their radiolar skeleton extension, dorsal pinnular and ventral radiolar appendages, parallel lamella, and companion chaetae on the thoracic neuropodia implies that different species groups are combined within Laonome . The monophyly of Laonome and the usefulness of the above characters of the branchial crown and other characters need to be verified. A revision of the genus Laonome was announced ( Capa 2007, Fitzhugh 2002, 2003).