Euclymeninae Arwidsson, 1906
Clymenura Verrill, 1900
Clymenura sp. 1
Voucher. SEA LION: station 3MFC and (tentatively) TOROA: station T4FA.
Diagnosis. SEA LION Voucher is a medium sized, incomplete specimen; 15mm long and 0.6mm wide for 11 chaetigers long fragment; preserved specimen light pink in colour. Chaetigers 1-6 about 1mm long (longer than wide) and distinctly separated by deep intersegmental grooves; chaetiger 7-8 of similar length but without pronounced segmental furrow; chaetigers 9 – 11 (end of fragment) much longer, fused. Chaetiger 8 with a distinct semi-circular glandular pad on dorsum as typical for this genus, pad is almost as long as the chaetiger 8.
Prostomium with well-developed cephalic plaque; cephalic rim with lateral (one on each side) and single mid-dorsal notches, anteriorly with shallow dips near mid-anterior peak (not developed into palpode). Nuchal organs wide and straight, slightly diverging anteriorly, about ½ the length of plaque, bordering a very low lying keel-like structure. The posterior half of cephalic plaque with faint horizontal lines (not fully developed into ridges).
Notochaetae capillaries of two types – long, smooth, very narrowly limbate chaetae (about 4 per fascicle) and more numerous (about 8 per fascicle) shorter simple, very thin capillaries. ). In chaetigers 1 -3 single neuropodial rostrate hook present, dentition of these uncini well developed; from chaetiger 4 about 10 rostrate uncini arranged in irregular single row, uncini with main fang and 4 small teeth, up to 4 thin barbells underneath the main fang; with manubrial constriction on its shaft. Posterior end and pygidium not observed. Tube not observed.
Additional notes: As part of taxonomic intercalibration exercise, additional specimen of Clymenura collected from Falkland Islands became available for examination. These possessed pygidial (although fragmented, no complete specimen was observed). The posterior ends of these specimens (otherwise consistent with SEA LION voucher described above) were of following form: 5 pre-pygidial rings (segments without chaetae); anal plaque with few thin cirri, largely differing in length with at least 3 long ones bordered by few shorter ones (three pygidia were available for examination, 3 long cirri were always present, but the number of shorter ones varied); cirri never developed on the dorsal side.
Remarks. Falkland Island specimens are consistent with genus Clymenura as they possess ventral pad on chaetiger 8; well-developed cephalic plaque and neuropodia of chaetigers 1-3 with a low number (one) of rostrate uncini. Currently, there are no known species of Clymenura from the region (Leiochone singularis Gravier, 1907 is considered a nomen dubium). Of the known Clymenura species, FI specimen are most similar to C. borealis from Northern Europe and C. lankesteri from Japan which also possess 5 or 5-6 pre-pygidial rings (other species have only 2-3), have cephalic rim with lateral and dorsal notches and reduced number of uncini in first chaetiger as well as reduced dentition in these uncini, the pygidial cirri are all long and thin. Falkland specimens appear to differ in not having ocelli and in possessing few anal cirri of varying length, although it is not clear if some are just missing. Falkland Island specimens likely represent a new species, but currently it is unclear if there are more than species of Clymenura present as no complete specimen has been found so far. For the same reason, it is unclear if the two voucher specimens represent the same species, but based on currently available morphological evidence, the two specimens share characters, mentioned above.
